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Modification of the 3He Phase Diagram by Anisotropic Disorder: Motivated by the recent prediction that uniaxially compressed aerogel can
stabilize the anisotropic A phase over the isotropic B phase, we measure the
pressure dependent superfluid fraction of 3He entrained in 10% axially
compressed, 98% porous aerogel. We observe that a broad region of the
temperature-pressure phase diagram is occupied by the metastable A phase. The
reappearance of the A phase on warming from the B phase, before superfluidity
is extinguished at Tc, is in contrast to its absence in uncompressed aerogel.
The phase diagram is modified from that of pure 3He, with the disappearance of
the polycritical point (PCP) and the appearance of a region of A phase
extending below the PCP of bulk 3He, even in zero applied magnetic field. The
expected alignment of the A phase texture by compression is not observed. | cond-mat_other |
Real-space Green's function approach for intrinsic losses in x-ray
spectra: Intrinsic inelastic losses in x-ray spectra originate from excitations in an
interacting electron system due to a suddenly created core-hole. These losses
characterize the features observed in x-ray photoemission spectra (XPS), as
well Here we present a complementary {\it ab initio} real-space Green's
function (RSGF) generalization of the Langreth cumulant in terms of the
dynamically screened core-hole interaction $W_c(\omega)$ and the independent
particle response function. We find that the cumulant kernel $\beta(\omega)$ is
analogous to XAS, but with the transition operator replaced by the core-hole
potential with monopole selection rules. The behavior reflects the analytic
structure of the loss function, with peaks near the zeros of the dielectric
function, consistent with delocalized quasi-boson excitations. The approach
simplifies when $W_c(\omega)$ is localized and spherically symmetric.
Illustrative results and comparisons are presented for the electron gas,
sodium, and some early transition metal compounds. | cond-mat_other |
Parametric Driving of Dark Solitons in Atomic Bose-Einstein Condensates: A dark soliton oscillating in an elongated harmonically-confined atomic
Bose-Einstein condensate continuously exchanges energy with the sound field.
Periodic optical `paddles' are employed to controllably enhance the sound
density and transfer energy to the soliton, analogous to parametric driving. In
the absence of damping, the amplitude of the soliton oscillations can be
dramatically reduced, whereas with damping, a driven soliton equilibrates as a
stable dark soliton with lower energy, thereby extending the soliton lifetime
up to the lifetime of the condensate. | cond-mat_other |
Glide and Superclimb of Dislocations in Solid $^4$He: Glide and climb of quantum dislocations under finite external stress,
variation of chemical potential and bias (geometrical slanting) in Peierls
potential are studied by Monte Carlo simulations of the effective string model.
We treat on unified ground quantum effects at finite temperatures $T$. Climb at
low $T$ is assisted by superflow along dislocation core -- {\it superclimb}.
Above some critical stress avalanche-type creation of kinks is found. It is
characterized by hysteretic behavior at low $T$. At finite biases gliding
dislocation remains rough even at lowest $T$ -- the behavior opposite to
non-slanted dislocations. In contrast to glide, superclimb is characterized by
quantum smooth state at low temperatures even for finite bias. In some
intermediate $T$-range giant values of the compressibility as well as
non-Luttinger type behavior of the core superfluid are observed. | cond-mat_other |
Bound states of attractive Bose-Einstein condensates in shallow traps in
two and three dimensions: Using variational and numerical solutions of the mean-field Gross-Pitaevskii
equation for attractive interaction (with cubic or Kerr nonlinearity) we show
that a stable bound state can appear in a Bose-Einstein condensate (BEC) in a
localized exponentially-screened radially-symmetric harmonic potential well in
two and three dimensions. We also consider an axially-symmetric configuration
with zero axial trap and a exponentially-screened radial trap so that the
resulting bound state can freely move along the axial direction like a soliton.
The binding of the present states in shallow wells is mostly due to the
nonlinear interaction with the trap playing a minor role. Hence these BEC
states are more suitable to study the effect of the nonlinear force on the
dynamics. We illustrate the highly nonlinear nature of breathing oscillation of
these states. Such bound states could be created in BECs and studied in the
laboratory with present knowhow. | cond-mat_other |
Effects of model approximations for electron, hole, and photon transport
in swift heavy ion tracks: The event-by-event Monte Carlo code, TREKIS, was recently developed to
describe excitation of the electron subsystems of solids in the nanometric
vicinity of a trajectory of a nonrelativistic swift heavy ion (SHI) decelerated
in the electronic stopping regime. The complex dielectric function (CDF)
formalism was applied in the used cross sections to account for collective
response of a matter to excitation. Using this model we investigate effects of
the basic assumptions on the modeled kinetics of the electronic subsystem which
ultimately determine parameters of an excited material in an SHI track. In
particular, (a) effects of different momentum dependencies of the CDF on
scattering of projectiles on the electron subsystem are investigated. The
'effective one-band' approximation for target electrons produces good
coincidence of the calculated electron mean free paths with those obtained in
experiments in metals. (b) Effects of collective response of a lattice appeared
to dominate in randomization of electron motion. We study how sensitive these
effects are to the target temperature. We also compare results of applications
of different model forms of (quasi-) elastic cross sections in simulations of
the ion track kinetics, e.g. those calculated taking into account optical
phonons in the CDF form vs. Mott's atomic cross sections. (c) It is
demonstrated that the kinetics of valence holes significantly affects
redistribution of the excess electronic energy in the vicinity of an SHI
trajectory as well as its conversion into lattice excitation in dielectrics and
semiconductors. (d) It is also shown that induced transport of photons
originated from radiative decay of core holes brings the excess energy faster
and farther away from the track core, however, the amount of this energy is
relatively small. | cond-mat_other |
A Single Cluster Covering for Dodecagonal Quasiperiodic Structure: Single cluster covering approach provides a plausible mechanism for the
formation and stability of octagonal and decagonal quasiperiodic structures.
For dodecagonal quasiperiodic pattern such a single cluster covering scheme is
still unavailable. Here we demonstrated that the ship tiling, one of the
dodecagonal quasiperioidic structures, can be constructed from one single
prototile with matching rules. A deflation procedure is devised by assigning
proper orientations to the tiles present in the ship tiling including regular
triangle, 30{\deg}-rhombus and square, and fourteen types of vertical
configurations have been identified in the deflated pattern, which fulfill the
closure condition under deflation and all result in a T-cluster centered at
vertex. This result can facilitate the study of physical properties of
dodecagonal quasicrystals. | cond-mat_other |
Dynamical symmetry in spinor Bose-Einstein condensates: We demonstrate that dynamical symmetry plays a crucial role in determining
the structure of the eigenspectra of spinor Bose-Einstein condensates (BECs).
In particular, the eigenspectra of spin- 1 and spin-2 BECs in the single-mode
approximation are shown to be completely determined by dynamical symmetries,
where a spin-2 BEC corresponds to the U(5) limit of the interacting boson model
in nuclear physics. The eigenspectrum of a spin-3 BEC is solved analytically
for a specific class of coupling constants, while it is shown that dynamical
symmetry alone is not enough to determine the spectrum for arbitrary coupling
constants. We also study the low-lying eigenspectra of spin-1 and spin-2 BECs
in the absence of external magnetic field, and find, in particular, that the
quasidegenerate spectra emerge for antiferromagnetic and cyclic phases. This
implies that these systems are highly susceptible to external perturbations and
may undergo symmetry-breaking transitions to other states upon increasing the
size of system. | cond-mat_other |
Optical whirlpool near absorbing metallic nanoparticle: The power-flow lines of light interacting with a metallic nanoparticle, in
the proximity of its plasmon resonance, form whirlpool-like nanoscale optical
vortices. Two different types of vortex have been detected. The outward vortex
first penetrates the particle near its centerline then, on exiting the
particle, the flow-lines turn away from the centerline and enter a spiral
trajectory. Outward vortexes are seen for the wavelengths shorter then the
plasmon resonance. For the wavelengths longer that the plasmon resonance the
vortex is inward: the power-flow lines pass around the sides of the particle
before turning towards the centerline and entering the particle to begin their
spiral trajectory. | cond-mat_other |
Induced Time-Reversal Symmetry Breaking Observed in Microwave Billiards: Using reciprocity, we investigate the breaking of time-reversal (T) symmetry
due to a ferrite embedded in a flat microwave billiard. Transmission spectra of
isolated single resonances are not sensitive to T-violation whereas those of
pairs of nearly degenerate resonances do depend on the direction of time. For
their theoretical description a scattering matrix model from nuclear physics is
used. The T-violating matrix elements of the effective Hamiltonian for the
microwave billiard with the embedded ferrite are determined experimentally as
functions of the magnetization of the ferrite. | cond-mat_other |
Reconsideration of Second Harmonic Generation from neat Air/Water
Interface: Broken of Kleinman Symmetry from Dipolar Contribution: It has been generally accepted that there are significant quadrupolar and
bulk contributions to the second harmonic generation (SHG) reflected from the
neat air/water interface, as well as common liquid interfaces. Because there
has been no general methodology to determine the quadrupolar and bulk
contributions to the SHG signal from a liquid interface, this conclusion was
reached based on the following two experimental phenomena. Namely, the broken
of the macroscopic Kleinman symmetry, and the significant temperature
dependence of the SHG signal from the neat air/water interface. However,
because sum frequency generation vibrational spectroscopy (SFG-VS) measurement
of the neat air/water interface observed no apparent temperature dependence,
the temperature dependence in the SHG measurement has been reexamined and
proven to be an experimental artifact. Here we present a complete microscopic
analysis of the susceptibility tensors of the air/water interface, and show
that dipolar contribution alone can be used to address the issue of broken of
the macroscopic Kleinman symmetry at the neat air/water interface. Using this
analysis, the orientation of the water molecules at the interface can be
obtained, and it is consistent with the measurement from SFG-VS. Therefore, the
key rationales to conclude significantly quadrupolar and bulk contributions to
the SHG signal of the neat air/water interface can no longer be considered as
valid as before. This new understanding of the air/water interface can shed
light on our understanding of the nonlinear optical responses from other
molecular interfaces as well. | cond-mat_other |
Rare-earth solid-state qubits: Quantum bits (qubits) are the basic building blocks of any quantum computer.
Superconducting qubits have been created with a 'top-down' approach that
integrates superconducting devices into macroscopic electrical circuits [1-3],
whereas electron-spin qubits have been demonstrated in quantum dots [4-6]. The
phase coherence time (Tau2) and the single qubit figure of merit (QM) of
superconducting and electron-spin qubits are similar -- Tau2 ~ microseconds and
QM ~10-1000 below 100mK -- and it should be possible to scale-up these systems,
which is essential for the development of any useful quantum computer.
Bottom-up approaches based on dilute ensembles of spins have achieved much
larger values of tau2 (up to tens of ms) [7, 8], but these systems cannot be
scaled up, although some proposals for qubits based on 2D nanostructures should
be scalable [9-11]. Here we report that a new family of spin qubits based on
rare-earth ions demonstrates values of Tau2 (~ 50microseconds) and QM (~1400)
at 2.5 K, which suggests that rare-earth qubits may, in principle, be suitable
for scalable quantum information processing at 4He temperatures. | cond-mat_other |
Tunneling time and Faraday/Kerr effects in $\mathcal{PT}$-symmetric
systems: We review the generalization of tunneling time and anomalous behaviour of
Faraday and Kerr rotation angles in parity and time
($\mathcal{P}\mathcal{T}$)-symmetric systems. Similarities of two phenomena are
discussed, both exhibit a phase transition-like anomalous behaviour in certain
range of model parameters. Anomalous behaviour of tunneling time and
Faraday/Kerr angles in $\mathcal{P}\mathcal{T}$-symmetric systems is caused by
the motion of poles of scattering amplitudes in energy/frequency complex plane. | cond-mat_other |
General Form of Magnetization Damping: Magnetization dynamics of a spin
system evolving nonadiabatically and out of equilibrium: Using an effective Hamiltonian including the Zeeman and internal
interactions, we describe the quantum theory of magnetization dynamics when the
spin system evolves non-adiabatically and out of equilibrium. The
Lewis-Riesenfeld dynamical invariant method is employed along with the
Liouville-von Neumann equation for the density matrix. We derive a dynamical
equation for magnetization defined with respect to the density operator with a
general form of magnetization damping that involves the non-equilibrium
contribution in addition to the Landau-Lifshitz-Gilbert equation. Two special
cases of the radiation-spin interaction and the spin-spin exchange interaction
are considered. For the radiation-spin interaction, the damping term is shown
to be of the Gilbert type, while in the spin-spin exchange interaction case the
results depend on a coupled chain of correlation functions. | cond-mat_other |
Quantum tunneling of magnetization in dipolar spin-1 condensates under
external fields: We study the macroscopic quantum tunneling of magnetization of the F=1 spinor
condensate interacting through dipole-dipole interaction with an external
magnetic field applied along the longitudinal or transverse direction. We show
that the ground state energy and the effective magnetic moment of the system
exhibit an interesting macroscopic quantum oscillation phenomenon originating
from the oscillating dependence of thermodynamic properties of the system on
the vacuum angle. Tunneling between two degenerate minima are analyzed by means
of an effective potential method and the periodic instanton method. | cond-mat_other |
Three component fermion pairing in two dimensions: We study pairing of an interacting three component Fermi gas in two
dimensions. By using a mean field theory to decouple the interactions between
different pairs of Fermi components, we study the free energy landscapes as a
function of various system parameters including chemical potentials, binding
energies, and temperature. We find that the s-wave pairing channel is
determined by both chemical potentials and the interaction strengths between
the three available channels. We find a second order thermal phase transition
and a series of first order quantum phase transitions for a homogenous system
as we change the parameters. In particular, for symmetric parameters, we find
the simultaneous existence of three superfluid orders as well as re-entrant
quantum phase transitions as we tune the parameters. | cond-mat_other |
Phonon-induced Exciton Dephasing in Quantum Dot Molecules: A new microscopic approach to the optical transitions in quantum dots and
quantum dot molecules, which accounts for both diagonal and non-diagonal
exciton-phonon interaction, is developed. The cumulant expansion of the linear
polarization is generalized to a multilevel system and is applied to
calculation of the full time dependence of the polarization and the absorption
spectrum. In particular, the broadening of zero-phonon lines is evaluated
directly. It is found that in some range of the dot distance real
phonon-assisted transitions between exciton states dominate the dephasing,
while virtual transitions are of minor importance. The influence of Coulomb
interaction, tunneling, and structural asymmetry on the exciton dephasing in
quantum dot molecules is analyzed. | cond-mat_other |
Capillary wave turbulence on a spherical fluid surface in low gravity: We report the observation of capillary wave turbulence on the surface of a
fluid layer in a low-gravity environment. In such conditions, the fluid covers
all the internal surface of the spherical container which is submitted to
random forcing. The surface wave amplitude displays power-law spectrum over two
decades in frequency, corresponding to wavelength from $mm$ to a few $cm$. This
spectrum is found in roughly good agreement with wave turbulence theory. Such a
large scale observation without gravity waves has never been reached during
ground experiments. When the forcing is periodic, two-dimensional spherical
patterns are observed on the fluid surface such as subharmonic stripes or
hexagons with wavelength satisfying the capillary wave dispersion relation. | cond-mat_other |
Imaging interferometry of excitons in two-dimensional structures: Can it
detect exciton coherence: Using the theory of imaging with partially coherent light, we derive general
expressions for different kinds of interferometric setups like double slit,
shift and mirror interference. We show that in all cases the interference
patterns depend not only on the point spread function of the imaging setup but
also strongly on the spatial emission pattern of the sample. Taking typical
experimentally observed spatial emission patterns into account, we can
reproduce at least qualitatively all the observed interference structures,
which have been interpreted as signatures for spontaneous long range coherence
of excitons, already for incoherent emitters. This requires a critical
reexamination of the previous work. | cond-mat_other |
Motion of discrete solitons assisted by nonlinearity management: We demonstrate that periodic modulation of the nonlinearity coefficient in
the discrete nonlinear Schr\"{o}dinger (DNLS) equation can strongly facilitate
creation of traveling solitons in the lattice. We predict this possibility in
an analytical form, and test it in direct simulations. Systematic simulations
reveal several generic dynamical regimes, depending on the amplitude and
frequency of the time modulation, and on initial thrust which sets the soliton
in motion. These regimes include irregular motion, regular motion of a decaying
soliton, and regular motion of a stable one. The motion may occur in both the
straight and reverse directions, relative to the initial thrust. In the case of
stable motion, extremely long simulations in a lattice with periodic boundary
conditions demonstrate that the soliton keeps moving as long as we can monitor
without any visible loss. Velocities of moving stable solitons are in good
agreement with the analytical prediction, which is based on requiring a
resonance between the ac drive and motion of the soliton through the periodic
potential. All the generic dynamical regimes are mapped in the model's
parameter space. Collisions between moving stable solitons are briefly
investigated too, with a conclusion that two different outcomes are possible:
elastic bounce, or bounce with mass transfer from one soliton to the other. The
model can be realized experimentally in a Bose-Einstein condensate trapped in a
deep optical lattice. | cond-mat_other |
Binding Energies of 6Li p-wave Feshbach Molecules: We present measurements of the binding energies of $^6$Li p-wave Feshbach
molecules formed in combinations of the (F = 1/2, m_F = +1/2), (1), and (F =
1/2, m_F = -1/2), (2), states. The binding energies scale linearly with
magnetic field detuning for all three resonances. The relative molecular
magnetic moments are found to be $113 \pm 7 \mu$K/G, $111 \pm 6 \mu$K/G and
$118 \pm 8 \mu$K/G for the (1)-(1), (1)-(2) and (2)-(2) resonances,
respectively, in good agreement with theoretical predictions. Closed channel
amplitudes and the size of the p-wave molecules are obtained theoretically from
full closed-coupled calculations. | cond-mat_other |
Tunable Quantum Fluctuation-Controlled Coherent Spin Dynamics: Temporal evolution of a macroscopic condensate of ultra cold atoms is usually
driven by mean field potentials, either due to scattering between atoms or due
to coupling to external fields; and coherent quantum dynamics have been
observed in various cold-atom experiments. In this article, we report results
of studies of a class of quantum spin dynamics which are purely driven by zero
point quantum fluctuations of spin collective coordinates. Unlike the usual
mean-field coherent dynamics, quantum fluctuation-controlled spin dynamics or
QFCSD studied here are very sensitive to variation of quantum fluctuations and
can be tuned by four to five order of magnitude using optical lattices. They
have unique dependence on optical lattice potential depths and quadratic Zeeman
fields. QFCSD can be potentially used to calibrate quantum fluctuations and
investigate correlated fluctuations and various universal scaling properties
near quantum critical points. | cond-mat_other |
A model for luminescence of localized state ensemble: A distribution function for localized carriers,
$f(E,T)=\frac{1}{e^{(E-E_a)/k_BT}+\tau_{tr}/\tau_r}$, is proposed by solving a
rate equation, in which, electrical carriers' generation, thermal escape,
recapture and radiative recombination are taken into account. Based on this
distribution function, a model is developed for luminescence from localized
state ensemble with a Gaussian-type density of states. The model reproduces
quantitatively all the anomalous temperature behaviors of localized state
luminescence. It reduces to the well-known band-tail and luminescence quenching
models under certain approximations. | cond-mat_other |
Estimating Probabilities of Default for Low Default Portfolios: For credit risk management purposes in general, and for allocation of
regulatory capital by banks in particular (Basel II), numerical assessments of
the credit-worthiness of borrowers are indispensable. These assessments are
expressed in terms of probabilities of default (PD) that should incorporate a
certain degree of conservatism in order to reflect the prudential risk
management style banks are required to apply. In case of credit portfolios that
did not at all suffer defaults, or very few defaults only over years, the
resulting naive zero or close to zero estimates would clearly not involve such
a sufficient conservatism. As an attempt to overcome this issue, we suggest the
"most prudent estimation" principle. This means to estimate the PDs by upper
confidence bounds while guaranteeing at the same time a PD ordering that
respects the differences in credit quality indicated by the rating grades. The
methodology is most easily applied under an assumption of independent default
events but can be adapted to the case of correlated defaults. | cond-mat_other |
On the Nature of Spin Currents: Full expressions for finite frequency spin and charge conductivity in Rashba
and Luttinger type systems are given. Whereas in the Rashba Hamiltonian the
spin conductivity has the same frequency dependence as the dielectric
polarizability, the Luttinger case is different. Moreover, for a generalized
Rashba-type coupling the two quantities also exhibit different frequency
dependencies. | cond-mat_other |
Local and non-local energy spectra of superfluid $^3$He turbulence: Below the phase transition temperature $Tc \simeq 10^{-3}$K He-3B has a
mixture of normal and superfluid components. Turbulence in this material is
carried predominantly by the superfluid component. We explore the statistical
properties of this quantum turbulence, stressing the differences from the
better known classical counterpart. To this aim we study the time-honored
Hall-Vinen-Bekarevich-Khalatnikov coarse-grained equations of superfluid
turbulence. We combine pseudo-spectral direct numerical simulations with
analytic considerations based on an integral closure for the energy flux. We
avoid the assumption of locality of the energy transfer which was used
previously in both analytic and numerical studies of the superfluid He-3B
turbulence. For T<0.37 Tc, with relatively weak mutual friction, we confirm the
previously found "subcritical" energy spectrum E(k), given by a superposition
of two power laws that can be approximated as $E(k)~ k^{-x}$ with an apparent
scaling exponent 5/3 <x(k)< 3. For T>0.37 Tc and with strong mutual friction,
we observed numerically and confirmed analytically the scale-invariant spectrum
$E(k)~ k^{-x}$ with a (k-independent) exponent x > 3 that gradually increases
with the temperature and reaches a value $x\simeq 9$ for $T\approx 0.72 Tc$. In
the near-critical regimes we discover a strong enhancement of intermittency
which exceeds by an order of magnitude the corresponding level in classical
hydrodynamic turbulence. | cond-mat_other |
Spin dynamics characterization in magnetic dots: The spin structure in a magnetic dot, which is an example of a quantum
few-body system, is studied as a function of exchange coupling strength and dot
size with in the semiclassical approximation on a discrete lattice. As the
exchange coupli ng is decreased or the size is increased, the ground state
undergoes a phase cha nge from a single domain ferromagnet to a spin vortex.
The line separating these two phases has been calculated numerically for small
system sizes. %, and analytically for larger dots. The dipolar interaction has
been fully included in our calculations. Magnon frequencies in such a dot have
also been calculated in both phases by the linearized equation of motion
method. These results have also been reproduced f rom the Fourier transform of
the spin autocorrelation function. From the magnon Density Of States (DOS), it
is possible to identify the magnetic phase of the dot. Furthermore, the magnon
modes have been characterized for both the ferromagnetic and the vortex phase,
and the magnon instability mechanism leading to the vortex-ferro transition has
also been identified. The results can also be used to compute finite
temperature magnetization or vort icity of magnetic dots. | cond-mat_other |
Bistability in a magnetic and nonmagnetic double-quantum-well structure
mediated by the magnetic phase transition: The hole distribution in a double quantum well (QW) structure consisting of a
magnetic and a nonmagnetic semiconductor QW is investigated as a function of
temperature, the energy shift between the QWs, and other relevant parameters.
When the itinerant holes mediate the ferromagnetic ordering, it is shown that a
bistable state can be formed through hole redistribution, resulting in a
significant change in the properties of the constituting magnetic QW (i.e., the
paramagnetic-ferromagnetic transition). The model calculation also indicates a
large window in the system parameter space where the bistability is possible.
Hence, this structure could form the basis of a stable memory element that may
be scaled down to a few hole regime. | cond-mat_other |
Theoretical Analysis of Functionally Graded Piezoelectric Thick-walled
Cylinder Subjected to Mechanical and Electric Loadings: In this paper, the theoretical analysis for a hollow thick-walled
functionally graded piezoelectric cylinder subjected to electric and mechanical
loads are developed. The cylinder consists of two materials (PZT4 and PVDF) and
the volume fraction of PZT4 is given in the three variable parameters power law
form. By using the Voigt method and the assumption of a uniform strain field
within the two linear elastic constituents, the complex hypergeometric
differential equation of the radial displacement is obtained. Then the
solutions of the radial displacement, the stresses, and the electric potential
are derived and solved. The method in this paper is more suitable for actual
engineering gradient piezoelectric materials, and the volume fraction function
can cover more complicated situations. Finally, the influence of the parameter
n in volume fraction on the mechanical behaviors are investigated, and the
difference between the circumferential and radial stresses is discussed to
reduce the stress concentration in the functionally graded piezoelectric
cylinder. | cond-mat_other |
Density Matrix Renormalization Group for Dummies: We describe the Density Matrix Renormalization Group algorithms for time
dependent and time independent Hamiltonians. This paper is a brief but
comprehensive introduction to the subject for anyone willing to enter in the
field or write the program source code from scratch. | cond-mat_other |
Quantum complementarity of microcavity polaritons: We present an experiment that probes polariton quantum correlations by
exploiting quantum complementarity. Specifically, we find that polaritons in
two distinct idler-modes interfere if and only if they share the same
signal-mode so that "which-way" information cannot be gathered. The
experimental results prove the existence of polariton pair correlations that
store the "which-way" information. This interpretation is confirmed by a
theoretical analysis of the measured interference visibility in terms of
quantum Langevin equations. | cond-mat_other |
Creating a supersolid in one-dimensional Bose mixtures: We identify a one-dimensional supersolid phase in a binary mixture of
near-hardcore bosons with weak, local inter-species repulsion. We find
realistic conditions under which such a phase, defined here as the coexistence
of quasi-superfluidity and quasi-charge density wave order, can be produced and
observed in finite ultra-cold atom systems in a harmonic trap. Our analysis is
based on Luttinger liquid theory supported with numerical calculations using
the time-evolving block decimation method. Clear experimental signatures of
these two orders can be found, respectively, in time-of-flight interference
patterns, and the structure factor S(k) derived from density correlations. | cond-mat_other |
Stability of superfluid and supersolid phases of dipolar bosons in
optical lattices: We perform a stability analysis of superfluid (SF) and supersolid (SS) phases
of polarized dipolar bosons in two-dimensional optical lattices at high filling
factors and zero temperature, and obtain the phase boundaries between SF,
checkerboard SS (CSS), striped SS (SSS), and collapse. We show that the phase
diagram can be explored through the application of an external field and the
tuning of its direction with respect to the optical lattice plane. In
particular, we find a transition between the CSS and SSS phases. | cond-mat_other |
Frenkel-Kontorova model with cold trapped ions: We study analytically and numerically the properties of one-dimensional chain
of cold ions placed in a periodic potential of optical lattice and global
harmonic potential of a trap. In close similarity with the Frenkel-Kontorova
model, a transition from sliding to pinned phase takes place with the increase
of the optical lattice potential for the density of ions incommensurate with
the lattice period. Quantum fluctuations lead to a quantum phase transition and
melting of pinned instanton glass phase at large values of dimensional Planck
constant. The obtained results are also relevant for a Wigner crystal placed in
a periodic potential. | cond-mat_other |
Pure spin current from one-photon absorption of linearly polarized light
in noncentrosymmetric semiconductors: We show that one-photon absorption of linearly polarized light should produce
pure spin currents in noncentrosymmetric semiconductors, including even bulk
GaAs. We present 14x14 k.p model calculations of the effect in GaAs, including
strain, and pseudopotential calculations of the effect in wurtzite CdSe. | cond-mat_other |
First-principles calculation of the Gilbert damping parameter via the
linear response formalism with application to magnetic transition-metals and
alloys: A method for the calculations of the Gilbert damping parameter $\alpha$ is
presented, which based on the linear response formalism, has been implemented
within the fully relativistic Korringa-Kohn-Rostoker band structure method in
combination with the coherent potential approximation alloy theory. To account
for thermal displacements of atoms as a scattering mechanism, an alloy-analogy
model is introduced. This allows the determination of $\alpha$ for various
types of materials, such as elemental magnetic systems and ordered magnetic
compounds at finite temperature, as well as for disordered magnetic alloys at
$T = 0$ K and above. The effects of spin-orbit coupling, chemical and
temperature induced structural disorder are analyzed. Calculations have been
performed for the 3$d$ transition-metals bcc Fe, hcp Co, and fcc Ni, their
binary alloys bcc Fe$_{1-x}$Co$_{x}$, fcc Ni$_{1-x}$Fe$_x$, fcc
Ni$_{1-x}$Co$_x$ and bcc Fe$_{1-x}$V$_{x}$, and for 5d impurities in
transition-metal alloys. All results are in satisfying agreement with
experiment. | cond-mat_other |
Aharonov-Bohm interferences from local deformations in graphene: One of the most interesting aspects of graphene is the tied relation between
structural and electronic properties. The observation of ripples in the
graphene samples both free standing and on a substrate has given rise to a very
active investigation around the membrane-like properties of graphene and the
origin of the ripples remains as one of the most interesting open problems in
the system. The interplay of structural and electronic properties is
successfully described by the modelling of curvature and elastic deformations
by fictitious gauge fields that have become an ex- perimental reality after the
suggestion that Landau levels can form associated to strain in graphene and the
subsequent experimental confirmation. Here we propose a device to detect
microstresses in graphene based on a scanning-tunneling-microscopy setup able
to measure Aharonov-Bohm inter- ferences at the nanometer scale. The
interferences to be observed in the local density of states are created by the
fictitious magnetic field associated to elastic deformations of the sample. | cond-mat_other |
Electron-nuclear spin dynamics of Ga$^{2+}$ paramagnetic centers probed
by spin dependent recombination: A master equation approach: Similar to nitrogen-vacancy centers in diamond and impurity atoms in silicon,
interstitial gallium deep paramagnetic centers in GaAsN have been proven to
have useful characteristics for the development of spintronic devices. Among
other interesting properties, under circularly polarized light, gallium centers
in GaAsN act as spin filters that dynamically polarize free and bound electrons
reaching record spin polarizations (100\%). Furthermore, the recent observation
of the amplification of the spin filtering effect under a Faraday configuration
magnetic field has suggested that the hyperfine interaction that couples bound
electrons and nuclei permits the optical manipulation of its nuclear spin
polarization. Even though the mechanisms behind the nuclear spin polarization
in gallium centers are fairly well understood, the origin of nuclear spin
relaxation and the formation of an Overhauser-like magnetic field remain
elusive. In this work we develop a model based on the master equation approach
to describe the evolution of electronic and nuclear spin polarizations of
gallium centers interacting with free electrons and holes. Our results are in
good agreement with existing experimental observations. In regard to the
nuclear spin relaxation, the roles of nuclear dipolar and quadrupolar
interactions are discussed. Our findings show that, besides the hyperfine
interaction, the spin relaxation mechanisms are key to understand the
amplification of the spin filtering effect and the appearance of the
Overhauser-like magnetic field. Based on our model's results we propose an
experimental protocol based on time resolved spectroscopy. It consists of a
pump-probe photoluminescence scheme that would allow the detection and the
tracing of the electron-nucleus flip-flops through time resolved PL
measurements. | cond-mat_other |
Comment on "Critique of the foundations of time-dependent density
functional theory" [Phys. Rev.A. 75, 022513 (2007)]: A recent paper (Phys. Rev A. 75, 022513 (2007), arXiv:cond-mat/0602020)
challenges exact time-dependent density functional theory (TDDFT) on several
grounds. We explain why these criticisms are either irrelevant or incorrect,
and that TDDFT is both formally exact and predictive. | cond-mat_other |
Spin Seebeck Effect: Amplification of Spin Waves by Thermal Torque: We observe amplification of spin-wave packets propagating along a film of
yttrium iron garnet (YIG) subject to a transverse temperature gradient. The
amplification is attributed to a spin-transfer thermal torque created by spin
currents generated by means of the spin Seebeck effect that acts on the
magnetization and opposes the relaxation. The experimental data are interpreted
with a simple theoretical model using spin-wave theory that gives an
amplification gain in very good agreement with measurements. | cond-mat_other |
Fundamental limits for non-destructive measurement of a single spin by
Faraday rotation: Faraday rotation being a dispersive effect, is commonly considered as the
method of choice for non-destructive detection of spin states. Nevertheless
Faraday rotation is inevitably accompanied by spin-flips induced by Raman
scattering, which compromises non-destructive detection. Here, we derive an
explicit general relation relating the Faraday rotation and the spin-flip Raman
scattering cross-sections, from which precise criteria for non-destructive
detection are established. It is shown that, even in ideal conditions,
non-destructive measurement of a single spin can be achieved only in
anisotropic media, or within an optical cavity. | cond-mat_other |
Deuteron Momentum Distribution in KD2HPO4: The momentum distribution in KD2PO4(DKDP) has been measured using neutron
Compton scattering above and below the weakly first order
paraelectric-ferroelectric phase transition(T=229K). There is very litte
difference between the two distributions, and no sign of the coherence over two
locations for the proton observed in the paraelectric phase, as in KH2PO4(KDP).
We conclude that the tunnel splitting must be much less than 20mev. The width
of the distribution indicates that the effective potential for DKDP is
significantly softer than that for KDP. As electronic structure calculations
indicate that the stiffness of the potential increases with the size of the
coherent region locally undergoing soft mode fluctuations, we conclude that
there is a mass dependent quantum coherence length in both systems. | cond-mat_other |
Are high-energy photoemission final states free-electron-like?: Three-dimensional (3D) electronic band structure is fundamental for
understanding a vast diversity of physical phenomena in solid-state systems,
including topological phases, interlayer interactions in van der Waals
materials, dimensionality-driven phase transitions, etc. Interpretation of
ARPES data in terms of 3D electron dispersions is commonly based on the
free-electron approximation for the photoemission final states. Our soft-X-ray
ARPES data on Ag metal reveals, however, that even at high excitation energies
the final states can be a way more complex, incorporating several Bloch waves
with different out-of-plane momenta. Such multiband final states manifest
themselves as a complex structure and excessive broadening of the spectral
peaks from 3D electron states. We analyse the origins of this phenomenon, and
trace it to other materials such as Si and GaN. Our findings are essential for
accurate determination of the 3D band structure over a wide range of materials
and excitation energies in the ARPES experiment. | cond-mat_other |
A consistent description of the iron dimer spectrum with a correlated
single-determinant wave function: We study the iron dimer by using an accurate ansatz for quantum chemical
calculations based on a simple variational wave function, defined by a single
geminal expanded in molecular orbitals and combined with a real space
correlation factor. By means of this approach we predict that, contrary to
previous expectations, the neutral ground state is $^7 \Delta$ while the ground
state of the anion is $^8 \Sigma_g^-$, hence explaining in a simple way a long
standing controversy in the interpretation of the experiments. Moreover, we
characterize consistently the states seen in the photoemission spectroscopy by
Leopold \emph{et al.}. It is shown that the non-dynamical correlations included
in the geminal expansion are relevant to correctly reproduce the energy
ordering of the low-lying spin states. | cond-mat_other |
Intense slow beams of bosonic potassium isotopes: We report on an experimental realization of a two-dimensional magneto-optical
trap (2D-MOT) that allows the generation of cold atomic beams of 39K and 41K
bosonic potassium isotopes. The high measured fluxes up to 1.0x10^11 atoms/s
and low atomic velocities around 33 m/s are well suited for a fast and reliable
3D-MOT loading, a basilar feature for new generation experiments on
Bose-Einstein condensation of dilute atomic samples. We also present a simple
multilevel theoretical model for the calculation of the light-induced force
acting on an atom moving in a MOT. The model gives a good agreement between
predicted and measured flux and velocity values for our 2D-MOT. | cond-mat_other |
Chiral charge-density-waves: We discovered the chirality of charge density waves (CDW) in 1T-TiSe$_2$ by
using scanning tunnelling microscopy (STM) and optical ellipsometry. We found
that the CDW intensity becomes $I{a_1}:I{a_2}:I{a_3} = 1:0.7 \pm 0.1:0.5 \pm
0.1$, where $Ia_i$ (i =1, 2, 3) is the amplitude of the tunnelling current
contributed by the CDWs. There were two states, in which the three intensity
peaks of the CDW decrease \textit{clockwise} and \textit{anticlockwise} when we
index each nesting vector in order of intensity in the Fourier transformation
of the STM images. The chirality in CDW results in the three-fold symmetry
breaking. Macroscopically, two-fold symmetry was indeed observed in optical
measurement. We propose the new generalized CDW chirality $H_{CDW} \equiv
{\boldmath $q_1$} \cdot ({\boldmath $q_2$}\times {\boldmath $q_3$})$, where
${\boldmath $q_i$}$ are the nesting vectors, which is independent of the
symmetry of components. The nonzero $H_{CDW}$ - the triple-${\boldmath $q$}$
vectors do not exist in an identical plane in the reciprocal space - should
induce a real-space chirality in CDW system. | cond-mat_other |
Spectroscopy of Strong-Pulse Superradiance in a Bose-Einstein condensate: We study experimentally superradiance in a Bose-Einstein condensate using a
two-frequency pump beam. By controlling the frequency difference between the
beam components, we measure the spectrum of the backward (energy-mismatched)
superradiant atomic modes. In addition, we show that the populations of these
modes display coherent time-dynamics. These results are compared to a
semi-classical model based on coupled Schroedinger-Maxwell equations. | cond-mat_other |
Thermal Fluctuations of the Electric Field in the Presence of Carrier
Drift: We consider a semiconductor in a non-equilibrium steady state, with a dc
current. On top of the stationary carrier motion there are fluctuations. It is
shown that the stationary motion of the carriers (i.e., their drift) can have a
profound effect on the electromagnetic field fluctuations in the bulk of the
sample as well as outside it, close to the surface (evanescent waves in the
near field). The effect is particularly pronounced near the plasma frequency.
This is because drift leads to a significant modification of the dispersion
relation for the bulk and surface plasmons. | cond-mat_other |
Topological Constraints on the Charge Distributions for the Thomson
Problem: The method of Morse theory is used to analyze the distributions of unit
charges interacting through a repulsive force and constrained to move on the
surface of a sphere -- the Thomson problem. We find that, due to topological
reasons, the system may organize itself in the form of pentagonal structures.
This gives a qualitative account for the interesting ``pentagonal buttons''
discovered in recent numerical work. | cond-mat_other |
Combined chips for atom-optics: We present experiments with Bose-Einstein condensates on a combined atom
chip. The combined structure consists of a large-scale "carrier chip" and
smaller "atom-optics chips", containing micron-sized elements. This allows us
to work with condensates very close to chip surfaces without suffering from
fragmentation or losses due to thermally driven spin flips. Precise
three-dimensional positioning and transport with constant trap frequencies are
described. Bose-Einstein condensates were manipulated with submicron accuracy
above atom-optics chips. As an application of atom chips, a direction sensitive
magnetic field microscope is demonstrated. | cond-mat_other |
Quantum Non-Demolition Detection of Strongly Correlated Systems: Preparation, manipulation, and detection of strongly correlated states of
quantum many body systems are among the most important goals and challenges of
modern physics. Ultracold atoms offer an unprecedented playground for
realization of these goals. Here we show how strongly correlated states of
ultracold atoms can be detected in a quantum non-demolition scheme, that is, in
the fundamentally least destructive way permitted by quantum mechanics. In our
method, spatially resolved components of atomic spins couple to quantum
polarization degrees of freedom of light. In this way quantum correlations of
matter are faithfully mapped on those of light; the latter can then be
efficiently measured using homodyne detection. We illustrate the power of such
spatially resolved quantum noise limited polarization measurement by applying
it to detect various standard and "exotic" types of antiferromagnetic order in
lattice systems and by indicating the feasibility of detection of superfluid
order in Fermi liquids. | cond-mat_other |
Energy flow of moving dissipative topological solitons: We study the energy flow due to the motion of topological solitons in
nonlinear extended systems in the presence of damping and driving. The total
field momentum contribution to the energy flux, which reduces the soliton
motion to that of a point particle, is insufficient. We identify an additional
exchange energy flux channel mediated by the spatial and temporal inhomogeneity
of the system state. In the well-known case of a DC external force the
corresponding exchange current is shown to be small but non-zero. For the case
of AC driving forces, which lead to a soliton ratchet, the exchange energy flux
mediates the complete energy flow of the system. We also consider the case of
combination of AC and DC external forces, as well as spatial discretization
effects. | cond-mat_other |
Comparison study of DFA and DMA methods in analysis of autocorrelations
in time series: Statistics of the Hurst scaling exponents calculated with the use of two
methods: recently introduced Detrended Moving Average Analysis(DMA) and
Detrended Fluctuation Analysis (DFA)are compared. Analysis is done for
artificial stochastic Brownian time series of various length and reveals
interesting statistical relationships between two methods. Good agreement
between DFA and DMA techniques is found for long time series $L\sim 10^{5}$,
however for shorter series we observe that two methods give different results
with no systematic relation between them. It is shown that, on the average, DMA
method overestimates the Hurst exponent comparing it with DFA technique. | cond-mat_other |
Quantum dynamics of two bosons in an anharmonic trap: Collective vs
internal excitations: This work deals with the effects of an anharmonic trap on an interacting
two-boson system in one dimension. Our primary focus is on the role of the
induced coupling between the center of mass and the relative motion as both
anharmonicity and the (repulsive) interaction strength are varied. The ground
state reveals a strong localization in the relative coordinate, counteracting
the tendency to fragment for stronger repulsion. To explore the quantum
dynamics, we study the system's response upon (i) exciting the harmonic ground
state by continuously switching on an additional anharmonicity, and (ii)
displacing the center of mass, this way triggering collective oscillations. The
interplay between collective and internal dynamics materializes in the collapse
of oscillations, which are explained in terms of few-mode models. | cond-mat_other |
Temporal dynamics of tunneling. Hydrodynamic approach: We use the hydrodynamic representation of the Gross -Pitaevskii/Nonlinear
Schroedinger equation in order to analyze the dynamics of macroscopic tunneling
process. We observe a tendency to a wave breaking and shock formation during
the early stages of the tunneling process. A blip in the density distribution
appears in the outskirts of the barrier and under proper conditions it may
transform into a bright soliton. Our approach, based on the theory of shock
formation in solutions of Burgers equation, allows us to find the parameters of
the ejected blip (or soliton if formed) including the velocity of its
propagation. The blip in the density is formed regardless of the value and sign
of the nonlinearity parameter. However a soliton may be formed only if this
parameter is negative (attraction) and large enough. A criterion is proposed.
An ejection of a soliton is also observed numerically. We demonstrate,
theoretically and numerically, controlled formation of soliton through
tunneling. The mass of the ejected soliton is controlled by the initial state. | cond-mat_other |
Nonlinear intraband tunneling of BEC in a cubic three-dimensional
lattice: The intra-band tunneling of a Bose-Einstein condensate between three
degenerate high-symmetry X-points of the Brillouin zone of a cubic optical
lattice is studied in the quantum regime by reduction to a three-mode model.
The mean-field approximation of the deduced model is described. Compared to the
previously reported two-dimensional (2D) case [Phys. Rev. A 75, 063628 (2007)],
which is reducible to the two-mode model, in the case under consideration there
exist a number of new stable stationary atomic distributions between the
X-points and a new critical lattice parameter. The quantum collapses and
revivals of the atomic population dynamics are absent for the experimentally
realizable time span. The 2D stationary configurations, embedded into the 3D
lattice, turn out to be always unstable, while existence of a stable 1D
distribution, where all atoms populate only one X-state, may serve as a
starting point in the experimental study of the nonlinear tunneling in the 3D
lattice. | cond-mat_other |
Evolution of a quantum spin system to its ground state: Role of
entanglement and interaction symmetry: We study the decoherence of two ferro- and antiferromagnetically coupled
spins that interact with a frustrated spin-bath environment in its ground
state. The conditions under which the two-spin system relaxes from the initial
spin-up - spin-down state towards its ground state are determined. It is shown
that the two-spin system relaxes to its ground state for narrow ranges of the
model parameters only. It is demonstrated that the symmetry of the coupling
between the two-spin system and the environment has an important effect on the
relaxation process. In particular, we show that if this coupling conserves the
magnetization, the two-spin system readily relaxes to its ground state whereas
a non-conserving coupling prevents the two-spin system from coming close to its
ground state. | cond-mat_other |
Comment on "Fully covariant radiation force on a polarizable particle": Recently Pieplow and Henkel (PH) (NJP \textbf{15} (2013) 023027) presented a
new fully covariant theory of the Casimir friction force acting on small
neutral particle moving parallel to flat surface. We compare results of this
theory with results which follow from a fully relativistic theory of friction
in plate-plate configurations in the limit when one plate is considered as
sufficiently rarefied. We show that there is the agreement between these
theories. | cond-mat_other |
Conditions for the Existence of Polaron States in Classical Molecular
Chains at Finite Temperatures: Today in many articles the polaron states are calculated in classical
molecular chains for zero temperature. At the same time it is assumed that
polaron properties do not change significantly, if the temperature is nonzero,
but much smaller than the characteristic energy equal to the depth of the
polaron level. However, the results of computational experiments lead us to
suggestion that in infinitely long chain the polaron is destroyed at any small
different from zero temperature. The paper is devoted to the resolution of
described "paradoxical" situation. | cond-mat_other |
Complex Envelope Soliton in Bose-Einstein Condensate with Time Dependent
Scattering Length: We elaborate on a general method to find complex envelope solitons in a cigar
shaped Bose-Einstein condensate in a trap. The procedure incorporates time
dependent scattering length, oscillator frequency and loss/gain. A variety of
time dependencies of the above parameters, akin to the ones occurring in the
experiments can be tackled. | cond-mat_other |
Importance of bath dynamics for decoherence in spin systems: We study the decoherence of two coupled spins that interact with a chaotic
spin-bath environment. It is shown that connectivity of spins in the bath is of
crucial importance for the decoherence of the central system. The previously
found phenomenon of two-step decoherence (Phys. Rev. Lett. {\bf 90}, 210401
(2003)) turns out to be typical for the bath with a slow enough dynamics or no
dynamics. For a generic random system with chaotic dynamics a conventional
exponential relaxation to the pointer states takes place. Our results confirm a
conjecture of Paz and Zurek (Phys. Rev. Lett. {\bf 82}, 5181 (1999)) that for
weak enough interactions the pointer states are eigenstates of the central
system. | cond-mat_other |
Self-induced density modulations in the free expansion of Bose-Einstein
condensates: We simulate numerically the free expansion of a repulsive Bose-Einstein
condensate with an initially Gaussian density profile. We find a self-similar
expansion only for weak inter-atomic repulsion. In contrast, for strong
repulsion we observe the spontaneous formation of a shock wave at the surface
followed by a significant depletion inside the cloud. In the expansion,
contrary to the case of a classical viscous gas, the quantum fluid can generate
radial rarefaction density waves with several minima and maxima. These
intriguing nonlinear effects, never observed yet in free-expansion experiments
with ultra-cold alkali-metal atoms, can be detected with the available setups. | cond-mat_other |
Continuum Mechanics for Quantum Many-Body Systems: The Linear Response
Regime: We derive a closed equation of motion for the current density of an
inhomogeneous quantum many-body system under the assumption that the
time-dependent wave function can be described as a geometric deformation of the
ground-state wave function. By describing the many-body system in terms of a
single collective field we provide an alternative to traditional approaches,
which emphasize one-particle orbitals. We refer to our approach as continuum
mechanics for quantum many-body systems. In the linear response regime, the
equation of motion for the displacement field becomes a linear fourth-order
integro-differential equation, whose only inputs are the one-particle density
matrix and the pair correlation function of the ground-state. The complexity of
this equation remains essentially unchanged as the number of particles
increases. We show that our equation of motion is a hermitian eigenvalue
problem, which admits a complete set of orthonormal eigenfunctions under a
scalar product that involves the ground-state density. Further, we show that
the excitation energies derived from this approach satisfy a sum rule which
guarantees the exactness of the integrated spectral strength. Our formulation
becomes exact for systems consisting of a single particle, and for any
many-body system in the high-frequency limit. The theory is illustrated by
explicit calculations for simple one- and two-particle systems. | cond-mat_other |
Comment on "Amplitude of waves in the Kelvin-wave cascade": In the recently published preprint arXiv:200.02610 Eltsov and L'vov
calculated the amplitudes of waves in the Kelvin-wave cascades. This returns us
to the rather old, but still unresolved dispute on the role of the tilt
symmetry and the locality in the Kelvin-wave cascade. The estimations by Eltsov
and L'vov show that the possible nonlocality of the energy flux in the
Kelvin-wave cascade has no essential effect on the Kelvin-wave cascade in the
3D vortex tangle. | cond-mat_other |
Spin-transfer mechanism of ferromagnetism in polymerized fullerenes: $Ab
initio$ calculations: A mechanism of the high temperature ferromagnetism in polymerized fullerenes
is suggested. It is assumed that some of the C$_{60}$ molecules in the crystal
become magnetically active due to spin and charge transfer from the
paramagnetic impurities (atoms or groups), such as hydrogen, fluorine, hydroxyl
group OH, amino group NH$_2$, or methyl group CH$_3$, dispersed in the
fullerene matrix. The exchange interaction between the spins localized on the
magnetically active fullerenes is evaluated using \textit{ab initio}
calculations. The nearest neighbour and next nearest neighbour exchange
interaction is found to be in the range $0.1\div 0.3 $ eV, that is, high enough
to account for the room temperature ferromagnetism. | cond-mat_other |
A Quantum Top Inside a Bose Josephson Junction: We consider an atomic quantum dot confined between two weakly-coupled
Bose-Einstein condensates, where the dot serves as an additional tunneling
channel. It is shown that the thus-embedded atomic quantum dot is a pseudospin
subject to an external torque, and therefore equivalent to a quantum top. We
demonstrate by numerical analysis of the time-dependent coupled evolution
equations that this microscopic quantum top is very sensitive to any deviation
from linear oscillatory behavior of the condensates. For sufficiently strong
dot-condensate coupling, the atomic quantum dot can induce or modify the
tunneling between the macroscopic condensates in the two wells. | cond-mat_other |
Dark state experiments with ultracold, deeply-bound triplet molecules: We examine dark quantum superposition states of weakly bound Rb2 Feshbach
molecules and tightly bound triplet Rb2 molecules in the rovibrational ground
state, created by subjecting a pure sample of Feshbach molecules in an optical
lattice to a bichromatic Raman laser field. We analyze both experimentally and
theoretically the creation and dynamics of these dark states. Coherent
wavepacket oscillations of deeply bound molecules in lattice sites, as observed
in one of our previous experiments, are suppressed due to laser-induced phase
locking of molecular levels. This can be understood as the appearance of a
novel multilevel dark state. In addition, the experimental methods developed
help to determine important properties of our coupled atom / laser system. | cond-mat_other |
Ground State and Tkachenko Modes of a Rapidly Rotating Bose-Einstein
Condensate in the Lowest Landau Level State: The Letter considers the ground state and the Tkachenko modes for a rapidly
rotating Bose-Einstein condensate (BEC), when its macroscopic wave function is
a coherent superposition of states analogous to the lowest Landau levels of a
charge in a magnetic field. As well as in type II superconductors close to the
critical magnetic field $H_{c2}$, this corresponds to a periodic vortex
lattice. The exact value of the shear elastic modulus of the vortex lattice,
which was known from the old works on type II superconductors, essentially
exceeds the values calculated recently for BEC. This is important for
comparison with observation of the Tkachenko mode in the rapidly rotating BEC. | cond-mat_other |
A Twisted Pair Cryogenic Filter: In low temperature transport measurements, there is frequently a need to
protect a device at cryogenic temperatures from thermal noise originating in
warmer parts of the experiment. There are also a wide range of experiments,
such as high precision transport measurements on low impedance devices, in
which a twisted-pair wiring configuration is useful to eliminate magnetic
pickup. Furthermore, with the rapid growth in complexity of cryogenic
experiments, as in the field of quantum computing, there is a need for more
filtered lines into a cryostat than are often available using the bulky low
temperature filters in use today. We describe a low cost filter that provides
the needed RF attenuation while allowing for tens of wires in a twisted pair
configuration with an RF-tight connection to the sample holder. Our filter
consists of manganin twisted pairs wrapped in copper tape with a light-tight
connection to the shield of the sample holder. We demonstrate agreement of our
filter with a theoretical model up to the noise floor of our measurement
apparatus (90 dB). We describe operation of our filter in noise thermometry
experiments down to 10 mK. | cond-mat_other |
The Moment Map: Nonlinear dynamics of density evolution via a few
moments: We explore situations in which certain stochastic and high-dimensional
deterministic systems behave effectively as low-dimensional dynamical systems.
We define and study moment maps, maps on spaces of low-order moments of
evolving distributions, as a means of understanding equations-free multiscale
algorithms for these systems. We demonstrate how nonlinearity arises in these
maps and how this results in the stabilization of metastable states. Examples
are shown for a hierarchy of models, ranging from simple stochastic
differential equations to molecular dynamics simulations of a particle in
contact with a heat bath. | cond-mat_other |
Optical properties of atomic Mott insulators: from slow light to
dynamical Casimir effects: We theoretically study the optical properties of a gas of ultracold,
coherently dressed three-level atoms in a Mott insulator phase of an optical
lattice. The vacuum state, the band dispersion and the absorption spectrum of
the polariton field can be controlled in real time by varying the amplitude and
the frequency of the dressing beam. In the weak dressing regime, the system
shows unique ultra-slow light propagation properties without absorption. In the
presence of a fast time modulation of the dressing amplitude, we predict a
significant emission of photon pairs by parametric amplification of the
polaritonic zero-point fluctuations. Quantitative considerations on the
experimental observability of such a dynamical Casimir effect are presented for
the most promising atomic species and level schemes. | cond-mat_other |
Intrinsic relation between ground-state fidelity and the
characterization of a quantum phase transition: The notion of fidelity in quantum information science has been recently
applied to analyze quantum phase transitions from the viewpoint of the ground
state (GS) overlap for various many-body systems. In this work, we unveil the
intrinsic relation between the GS fidelity and the derivatives of GS energy and
find that they play equivalent role in identifying the quantum phase
transition. The general connection between the two approaches enables us to
understand the different singularity and scaling behaviors of fidelity
exhibited in various systems on general grounds. Our general conclusions are
illustrated via several quantum spin models which exhibit different kinds of
QPTs. | cond-mat_other |
Coherent electronic transfer in quantum dot systems using adiabatic
passage: We describe a scheme for using an all-electrical, rapid, adiabatic population
transfer between two spatially separated dots in a triple-quantum dot system.
The electron spends no time in the middle dot and does not change its energy
during the transfer process. Although a coherent population transfer method,
this scheme may well prove useful in incoherent electronic computation (for
example quantum-dot cellular automata) where it may provide a coherent
advantage to an otherwise incoherent device. It can also be thought of as a
limiting case of type II quantum computing, where sufficient coherence exists
for a single gate operation, but not for the preservation of superpositions
after the operation. We extend our analysis to the case of many intervening
dots and address the issue of transporting quantum information through a
multi-dot system. | cond-mat_other |
Molecular-dynamics simulation of clustering processes in sea-ice floes: In seasonally ice-covered seas and along the margins of perennial ice pack,
i.e. in regions with medium ice concentrations, the ice cover typically
consists of separate floes interacting with each other by inelastic collisions.
In this paper, hitherto unexplored analogies between this type of ice cover and
two-dimensional granular gases are used to formulate a model of ice dynamics at
the floe level. The model consists of: (i) momentum equations for floe motion
between collisions, formulated in the form of a Stokes-flow problem, with
floe-size dependent time constant and equilibrium velocity, and (ii) hard-disk
collision model. The numerical algorithm developed is suitable for simulating
particle-laden flow of $N$ disk-shaped floes with arbitrary size distribution.
The model is applied to study clustering phenomena in sea ice with power-law
floe-size distribution. In particular, the influence of the average ice
concentration $\bar{A}$ on the formation and characteristics of clusters is
analyzed in detail. The results show the existence of two regimes, at low and
high ice concentration, differing in terms of the exponents of the cluster-size
distribution and of the size of the largest cluster. | cond-mat_other |
Two roads to antispacetime in polar distorted B phase: Kibble wall and
half-quantum vortex: We consider the emergent tetrad gravity and the analog of antispacetime
realized in the recent experiments ( J.T. Makinen, et al., Nat. Comm. 10, 237
(2019)) on the composite defects in superfluid $^3$He: the Kibble walls bounded
by strings (the half quantum vortices). The antispacetime can be reached in two
different ways: by the "safe" route around the Alice string or by dangerous
route across the Kibble wall. This consideration also suggests the scenario of
the formation of the discrete symmetry -- the parity $P$ in Dirac equations --
from the continuous symmetry existing on the more fundamental level. | cond-mat_other |
Collisions between tunable halo dimers: exploring an elementary
four-body process with identical bosons: We study inelastic collisions in a pure, trapped sample of Feshbach molecules
made of bosonic cesium atoms in the quantum halo regime. We measure the
relaxation rate coefficient for decay to lower-lying molecular states and study
the dependence on scattering length and temperature. We identify a pronounced
loss minimum with varying scattering length along with a further suppression of
loss with decreasing temperature. Our observations provide insight into the
physics of a few-body quantum system that consists of four identical bosons at
large values of the two-body scattering length. | cond-mat_other |
Single-atom doping for quantum device development in diamond and silicon: The ability to inject dopant atoms with high spatial resolution, flexibility
in dopant species and high single ion detection fidelity opens opportunities
for the study of dopant fluctuation effects and the development of devices in
which function is based on the manipulation of quantum states in single atoms,
such as proposed quantum computers. We describe a single atom injector, in
which the imaging and alignment capabilities of a scanning force microscope
(SFM) are integrated with ion beams from a series of ion sources and with
sensitive detection of current transients induced by incident ions. Ion beams
are collimated by a small hole in the SFM tip and current changes induced by
single ion impacts in transistor channels enable reliable detection of single
ion hits. We discuss resolution limiting factors in ion placement and
processing and paths to single atom (and color center) array formation for
systematic testing of quantum computer architectures in silicon and diamond. | cond-mat_other |
Energy concentration in composite quantum systems: The spontaneous emission of photons from optical cavities and from trapped
atoms has been studied extensively in the framework of quantum optics.
Theoretical predictions based on the rotating wave approximation (RWA) are in
general in very good agreement with experimental findings. However, current
experiments aim at combining better and better cavities with large numbers of
tightly confined atoms. Here we predict an energy concentrating mechanism in
the behavior of such a composite quantum system which cannot be described by
the RWA. Its result is the continuous leakage of photons through the cavity
mirrors, even in the absence of external driving. We conclude with a discussion
of the predicted phenomenon in the context of thermodynamics. | cond-mat_other |
A controllable nanomechanical memory element: We report the realization of a completely controllable high-speed
nanomechanical memory element fabricated from single-crystal silicon wafers.
This element consists of a doubly-clamped suspended nanomechanical beam
structure, which can be made to switch controllably between two stable and
distinct states at a single frequency in the megahertz range. Because of their
sub-micron size and high normal-mode frequencies, these nanomechanical memory
elements offer the potential to rival the current state-of-the-art electronic
data storage and processing. | cond-mat_other |
On the Transition to Turbulence of Oscillatory Flow of Liquid Helium-4: Oscillating solid bodies have frequently been used for studying the
properties of normal and superfluid helium. In particular, the transition from
laminar flow to turbulence has attracted much interest recently. The purpose of
this note is to review several central features of this transition in
oscillatory flow, which have been inaccurately formulated in some recent work. | cond-mat_other |
Motional Averaging of Nuclear Resonance in a Field Gradient: The traditional view of nuclear-spin decoherence in a field gradient due to
molecular self-diffusion is challenged on the basis of temperature dependence
of the linewidth, which demonstrates different behaviors between liquids and
gases. The conventional theory predicts that in a fluid, linewidth should
increase with temperature; however, in gases we observed the opposite behavior.
This surprising behavior can be explained using a more detailed theoretical
description of the dephasing function that accounts for position
autocorrelation effects. | cond-mat_other |
Electron dynamics in vacancy islands: The dynamics of Ag(111) surface state electrons confined to nanoscale
hexagonal and triangular vacancy islands are investigated using scanning
tunneling spectroscopy. The lifetimes of quantised states with significant
amplitude near the centers of the vacancies are weakly affected by the geometry
of the confining cavity. A model that includes the dependence of the lifetime
on electron energy, vacancy size, step reflectivity and the phase coherence
length describes the results well. For vacancy islands with areas in the range
$\approx 40$--$220 {\rm nm}^2$ lossy scattering is the dominant
lifetime-limiting process. This result and a corrected analysis of published
experimental data improve the consistency of experimental and calculated
surface state lifetimes. | cond-mat_other |
Current-induced interactions of multiple domain walls in magnetic
quantum wires: We show that an applied charge current in a magnetic nanowire containing
domain walls (DWs) results in an interaction between DWs mediated by
spin-dependent interferences of the scattered carriers. The energy and torque
associated with this interaction show an oscillatory behaviour as a function of
the mutual DWs orientations and separations, thus affecting the DWs'
arrangements and shapes. Based on the derived DWs interaction energy and torque
we calculate DW dynamics and uncover potential applications of interacting DWs
as a tunable nano-mechanical oscillator. We also discuss the effect of
impurities on the DW interaction. | cond-mat_other |
Natural Negative-Refractive-Index Materials: Our calculation shows that negative refractive index (NRI), which was known
to exist only in metamaterials in the past, can be found in Dirac semimetals
(DSM). Electrons in DSM have zero effective mass and hence the system carries
no nominal energy scale. Therefore, unlike those of ordinary materials, the
electromagnetic responses of the electrons in DSM will not be overwhelmed by
the physical effects related to electron mass. NRI is induced by the
combination of the quantum effect of vacuum polarization and its finite
temperature correction which is proportional to $T^4$ at low temperature. It is
a phenomenon of resonance between the incident light and the unique structure
of Dirac cones, which allows numerous states to participate in electron-hole
pair production excited by the incident light with similar dispersion relation
to that of Dirac cones. NRI phenomenon of DSM manifests in an extensive range
of photon frequency and wave number and can be observed around giga Hertz range
at temperature slightly higher than room temperature. | cond-mat_other |
An Investigation of Mean-field Effects for a Bose Condensate in an
Optical Lattice: This paper presents a mean-field numerical analysis, using the full
three-dimensional time-dependent Gross-Pitaevskii equation (GPE), of an
experiment carried out by Orzel et al. [Science 291, 2386 (2001)] intended to
show number squeezing in a gaseous Bose-Einstein condensate in an optical
lattice. The motivation for the present work is to elucidate the role of
mean-field effects in understanding the experimental results of this work and
those of related experiments. We show that the non-adiabatic loading of atoms
into optical lattices reproduces many of the main results of the Orzel et al.
experiment, including both loss of interference patterns as laser intensity is
increased and their regeneration when intensities are lowered. The
non-adiabaticity found in the GPE simulations manifests itself primarily in a
coupling between the transverse and longitudinal dynamics, indicating that
one-dimensional approximations are inadequate to model the experiment. | cond-mat_other |
The free surface of superfluid 4He at zero temperature: The structure and energetics of the free surface of superfluid $^4$He are
studied using the diffusion Monte Carlo method. Extending a previous
calculation by Vall\'es and Schmidt, which used the Green's function Monte
Carlo method, we study the surface of liquid $^4$He within a slab geometry
using a larger number of particles in the slab and an updated interatomic
potential. The surface tension is accurately estimated from the energy of slabs
of increasing surface density and its value is close to one of the two existing
experimental values. Results for the density profiles allow for the calculation
of the surface width which shows an overall agreement with recent experimental
data. The dependence on the transverse direction to the surface of other
properties such as the two-body radial distribution function, structure factor,
and one-body density matrix is also studied. The condensate fraction, extracted
from the asymptotic behavior of the one-body density matrix, shows an
unambiguous enhancement when approaching the surface. | cond-mat_other |
Topological Constraints on the Charge Distributions for the Thomson
Problem: The method of Morse theory is used to analyze the distributions of unit
charges interacting through a repulsive force and constrained to move on the
surface of a sphere -- the Thomson problem. We find that, due to topological
reasons, the system may organize itself in the form of pentagonal structures.
This gives a qualitative account for the interesting ``pentagonal buttons''
discovered in recent numerical work. | cond-mat_other |
Measuring the spin polarization and Zeeman energy of a spin-polarized
electron gas: Comparison between Raman scattering and photoluminescence: We compare resonant electronic Raman scattering and photoluminescence
measurements for the characterization of a spin-polarized two-dimensional
electron gas embedded in $\text{Cd}_{1-x}\text{Mn}_x\text{Te}$ single quantum
wells. From Raman scattering by single-particle excitations in a zero magnetic
field, we measure the Fermi velocity and then obtain the Fermi energy (as well
as the electron density), which is comparable to that extracted from
photoluminescence for moderate electron densities, assuming a bare band-edge
mass. At large electron densities, the Fermi energies derived from Raman
scattering and photoluminescence differ. For an applied in-plane magnetic field
and zero wave vector transferred to the electron gas, Raman scattering spectra
show peaks at both the Zeeman energy $Z$, resulting from collective excitations
of the spin-polarized electron gas, and the one electron spin-flip energy
$Z^*$. Magneto-photoluminescence spectra show conduction band splitting that
are equivalent to $Z$, suggesting that collective effects are present in the
photoluminescence spectra. Assuming (as before) an uncorrected mass, the degree
of spin polarization $\zeta$ determined from the magneto-photoluminescence
lineshape is found to differ from that derived from the magnetic field
dependent Raman scattering measurements for large electron densities. We
attribute the discrepancy in measuring $\zeta$ and the Fermi energy to the
renormalized mass resulting from many-body electron-electron interactions. | cond-mat_other |
Bipartite Yule Processes in Collections of Journal Papers: Collections of journal papers, often referred to as 'citation networks', can
be modeled as a collection of coupled bipartite networks which tend to exhibit
linear growth and preferential attachment as papers are added to the
collection. Assuming primary nodes in the first partition and secondary nodes
in the second partition, the basic bipartite Yule process assumes that as each
primary node is added to the network, it links to multiple secondary nodes, and
with probability, $\alpha$, each new link may connect to a newly appearing
secondary node. The number of links from a new primary node follows some
distribution that is a characteristic of the specific network. Links to
existing secondary nodes follow a preferential attachment rule. With
modifications to adapt to specific networks, bipartite Yule processes simulate
networks that can be validated against actual networks using a wide variety of
network metrics. The application of bipartite Yule processes to the simulation
of paper-reference networks and paper-author networks is demonstrated and
simulation results are shown to mimic networks from actual collections of
papers across several network metrics. | cond-mat_other |
Quantum fluid effects and parametric instabilities in microcavities: We present a description of the non-equilibrium properties of a microcavity
polariton fluid, injected by a nearly-resonant continuous wave pump laser. In
the first part, we point out the interplay between the peculiar dispersion of
the Bogolubov-like polariton excitations and the onset of polariton parametric
instabilities. We show how collective excitation spectra having no counterpart
in equilibrium systems can be observed by tuning the excitation angle and
frequency. In the second part, we explain the impact of these collective
excitations on the in-plane propagation of the polariton fluid. We show that
the resonant Rayleigh scattering induced by artificial or natural defects is a
very sensitive tool to show fascinating effects such as polariton superfluidity
or polariton Cherenkov effect. We present a comprehensive set of predicted
far-field and near-field images for the resonant Rayleigh scattering emission. | cond-mat_other |
Transport and recombination through weakly coupled localized spin pairs
in semiconductors during coherent spin excitation: Semi-analytical predictions for the transients of spin-dependent transport
and recombination rates through localized states in semiconductors during
coherent electron spin excitation are made for the case of weakly spin-coupled
charge carrier ensembles. The results show that the on-resonant Rabi frequency
of electrically or optically detected spin-oscillation doubles abruptly as the
strength of the resonant microwave field gamma B_1 exceeds the Larmor frequency
separation within the pair of charge carrier states between which the transport
or recombination transition takes place. For the case of a Larmor frequency
separation of the order of gamma B_1 and arbitrary excitation frequencies, the
charge carrier pairs exhibit four different nutation frequencies. From the
calculations, a simple set of equations for the prediction of these frequencies
is derived. | cond-mat_other |
Quantum Monte Carlo study of ring-shaped polariton parametric
luminescence in a semiconductor microcavity: We present a quantum Monte Carlo study of the quantum correlations in the
parametric luminescence from semiconductor microcavities in the strong
exciton-photon coupling regime. As already demonstrated in recent experiments,
a ring-shaped emission is obtained by applying two identical pump beams with
opposite in-plane wavevectors, providing symmetrical signal and idler beams
with opposite in-plane wavevectors on the ring. We study the squeezing of the
signal-idler difference noise across the parametric instability threshold,
accounting for the radiative and non-radiative losses, multiple scattering and
static disorder. We compare the results of the complete multimode Monte Carlo
simulations with a simplified linearized quantum Langevin analytical model. | cond-mat_other |
Effect of interactions on the localization of a Bose-Einstein condensate
in a quasi-periodic lattice: The transport properties of a Bose-Einstein condensate in a 1D incommensurate
bichromatic lattice are investigated both theoretically and experimentally. We
observe a blockage of the center of mass motion with low atom number, and a
return of motion when the atom number is increased. Solutions of the
Gross-Pitaevskii equation show how the localization due to the quasi-disorder
introduced by the incommensurate bichromatic lattice is affected by the
interactions. | cond-mat_other |
Alignment of the Diamond Nitrogen Vacancy Center by Strain Engineering: The nitrogen vacancy (NV) center in diamond is a sensitive probe of magnetic
field and a promising qubit candidate for quantum information processing. The
performance of many NV-based devices improves by aligning the NV(s) parallel to
a single crystallographic direction. Using ab initio theoretical techniques, we
show that NV orientation can be controlled by high-temperature annealing in the
presence of strain under currently accessible experimental conditions. We find
that $(89\pm7)\%$ of NVs align along the [111] crystallographic direction under
2\% compressive biaxial strain (perpendicular to [111]) and an annealing
temperature of 970$^\circ$C. | cond-mat_other |
Current-induced spin torques in III-V ferromagnetic semiconductors: We formulate a theory of current-induced spin torques in inhomogeneous III-V
ferromagnetic semiconductors. The carrier spin-3/2 and large spin-orbit
interaction, leading to spin non-conservation, introduce significant conceptual
differences from spin torques in ferromagnetic metals. We determine the spin
density in an electric field in the weak momentum scattering regime,
demonstrating that the torque on the magnetization is intimately related to
spin precession under the action of both the spin-orbit interaction and the
exchange field characteristic of ferromagnetism. The spin polarization excited
by the electric field is smaller than in ferromagnetic metals and, due to lack
of angular momentum conservation, cannot be expressed in a simple closed
vectorial form. Remarkably, scalar and spin-dependent scattering do not affect
the result. We use our results to estimate the velocity of current-driven
domain walls. | cond-mat_other |
Electron inelastic mean free paths in condensed matter down to a few
electronvolts: A method is reported for a simple, yet reliable, calculation of electron
inelastic mean free paths in condensed phase insulating and conducting
materials, from the very low energies of hot electrons up to the high energies
characteristic of electron beams. Through a detailed consideration of the
energy transferred by the projectile in individual and collective electronic
excitations, as well as ionizations, together with the inclusion of higher
order corrections to the results provided by the dielectric formalism,
inelastic mean free paths are calculated for water, aluminum, gold and copper
in excellent agreement with the available experimental data, even at the
elusive very low energy region. These results are important due to the crucial
role played by low energy electrons in radiobiology (owing to their relevant
effects in biodamage), and also in order to assess the not yet elucidated
disagreement between older and recent measurements of low energy electron mean
free paths in metals (which are relevant for low energy electron transport and
effects in nanostructured devices). | cond-mat_other |
Numerical Study on Entrance Length in Thermal Counterflow of Superfluid
$^4$He: Three-dimensional numerical simulations in a square duct were conducted to
investigate entrance lengths of normal fluid and superfluid flows in a thermal
counterflow of superfluid $^4$He. The two fluids were coarse-grained by using
the Hall-Vinen-Bekharevich-Khalatnikov (HVBK) model and were coupled through
mutual friction. We solved the HVBK equations by parameterizing the coefficient
of the mutual friction to consider the vortex line density. A uniform mutual
friction parameter was assumed in the streamwise direction. Our simulation
showed that the entrance length of the normal fluid from a hot end becomes
shorter than that of a single normal fluid due to the mutual friction with the
parabolically developed superfluid flow near the hot end. As the mutual
friction increases, the entrance length decreases. Same as that, the entrance
length of the superfluid from a cold end is affected by the strength of the
mutual friction due to the parabolically developed normal fluid flow near the
cold end. Aside from the entrance effect, the realized condition of a
tail-flattened flow is discussed by parameterizing the superfluid turbulent
eddy viscosity and the mutual friction. | cond-mat_other |
Many-body perturbation theory using the density-functional concept:
beyond the GW approximation: We propose an alternative formulation of Many-Body Perturbation Theory that
uses the density-functional concept. Instead of the usual four-point integral
equation for the polarizability, we obtain a two-point one, that leads to
excellent optical absorption and energy loss spectra. The corresponding
three-point vertex function and self-energy are then simply calculated via an
integration, for any level of approximation. Moreover, we show the direct
impact of this formulation on the time-dependent density-functional theory.
Numerical results for the band gap of bulk silicon and solid argon illustrate
corrections beyond the GW approximation for the self-energy. | cond-mat_other |
Influence of the substrate lattice structure on the formation of Quantum
Well States in thin In and Pb films on silicon: The substrate lattice structure may have a considerable influence on the
formation of quantum well states in a metal overlayer material. Here we study
three model systems using angle resolved photoemission and low energy electron
diffraction: indium films on Si(111) and indium and lead on Si(100). Data are
compared with theoretical predictions based on density functional theory. We
find that the interaction between the substrate and the overlayer strongly
influences the formation of quantum well states; indium layers only exhibit
well defined quantum well states when the layer relaxes from an initial
face-centered cubic to the bulk body-centered tetragonal lattice structure. For
Pb layers on Si(100) a change in growth orientation inhibits the formations of
quantum well states in films thicker than 2 ML. | cond-mat_other |
Supersolids in one dimensional Bose Fermi mixtures: Using quantum Monte Carlo simulations, we study a mixture of bosons and
fermions loaded on an optical lattice. With simple on-site repulsive
interactions, this system can be driven into a solid phase. We dope this phase
and, in analogy with pure bosonic systems, identify the conditions under which
the bosons enter a supersolid phase, i.e., exhibiting at the same time charge
density wave and superfluid order. We perform finite size scaling analysis to
confirm the presence of a supersolid phase and discuss its properties, showing
that it is a collective phase that also involve phase coherence of the
fermions. | cond-mat_other |
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