Dear subscribers,
Andy Ferris compiled this week's abstracts. There are 29 new preprints and 5
replacements.
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arXiv:0908.3015
Date: Thu, 20 Aug 2009 21:00:00 GMT (673kb)
Title: Universal Thermometry for Trapped Quantum Gases Based on Number
Fluctuations
Authors: Qi Zhou and Tin-Lun Ho
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures
\\
We show that by using a generalized of fluctuation-dissipation theorem, one
can determine the temperature of a trapped quantum gases (with or without
optical lattice) by number fluctuations in the interior of the gas. We show
that this scheme is fast convergent, requiring averaging over 50 samples to
achieve 3% accuracy. Moreover, the accuracy of the scheme is unaffected by the
presence of photon shot noise. This method also enables one to map out magnetic
susceptibility of spin systems as a function of chemical potential and
temperature.
\\ ( http://arxiv.org/abs/0908.3015 , 673kb)
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arXiv:0908.3033
Date: Fri, 21 Aug 2009 07:44:57 GMT (2763kb)
Title: Intrinsic instability at the Bose-Einstein condensation of bosonic
quasiparticles in magnetic insulators
Authors: A. Schilling
Categories: cond-mat.str-el cond-mat.quant-gas
Comments: 10 figures, 74 references
\\
Starting from a phenomenological standard energy functional to describe the
condensation of a dilute gas of bosonic quasiparticles in magnetic insulators,
we find that the inclusion of a perturbation term that explicitly violates the
axial symmetry significantly modifies the details of the resulting Bose
Einstein condensation. Systems with an originally axial symmetry must show an
intrinsic tendency to spontaneously violate this symmetry as soon as the
condensation sets in, and the phase transition at the respective critical field
may even become of first order. We can explain a number of features in the
experimental data of various insulating spin systems, such as a slightly
nonlinear magnetization near the critical field as well as hysteresis effects
and peculiarities in the energy-level scheme of TlCuCl3. We also offer a
consistent explanation for certain anomalies in the magnetocaloric effect and
in the magnetization of BaCuSi2O6 by assuming a spontaneous violation of axial
symmetry at the magnetic phase transition on an energy scale of about 1
micro-eV. The resulting anisotropy gap in the magnetic excitation spectrum,
that inevitably forms at the critical field of all such systems, lifts the
linear Goldstone mode and is therefore seriously limiting the lifetime of
magnetic condensates to a few nanoseconds at most.
\\ ( http://arxiv.org/abs/0908.3033 , 2763kb)
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arXiv:0908.3040
Date: Fri, 21 Aug 2009 01:48:20 GMT (541kb)
Title: Bose-Einstein condensation of trapped polaritons in 2D electron-hole
systems in a high magnetic field
Authors: Oleg L. Berman, Roman Ya. Kezerashvili, and Yurii E. Lozovik
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: 16 pages, 6 figures. accepted in Physical Review B
\\
The Bose-Einstein condensation (BEC) of magnetoexcitonic polaritons in
two-dimensional (2D) electron-hole system embedded in a semiconductor
microcavity in a high magnetic field $B$ is predicted. There are two physical
realizations of 2D electron-hole system under consideration: a graphene layer
and quantum well (QW). A 2D gas of magnetoexcitonic polaritons is considered in
a planar harmonic potential trap. Two possible physical realizations of this
trapping potential are assumed: inhomogeneous local stress or harmonic electric
field potential applied to excitons and a parabolic shape of the semiconductor
cavity causing the trapping of microcavity photons. The effective Hamiltonian
of the ideal gas of cavity polaritons in a QW and graphene in a high magnetic
field and the BEC temperature as functions of magnetic field are obtained. It
is shown that the effective polariton mass $M_{\rm eff}$ increases with
magnetic field as $B^{1/2}$. The BEC critical temperature $T_{c}^{(0)}$
decreases as $B^{-1/4}$ and increases with the spring constant of the parabolic
trap. The Rabi splitting related to the creation of a magnetoexciton in a high
magnetic field in graphene and QW is obtained. It is shown that Rabi splitting
in graphene can be controlled by the external magnetic field since it is
proportional to $B^{-1/4}$, while in a QW the Rabi splitting does not depend on
the magnetic field when it is strong.
\\ ( http://arxiv.org/abs/0908.3040 , 541kb)
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arXiv:0908.3046
Date: Fri, 21 Aug 2009 04:38:46 GMT (64kb,D)
Title: Spin gradient thermometry for ultracold atoms in optical lattices
Authors: David M. Weld, Patrick Medley, Hirokazu Miyake, David Hucul, David E.
Pritchard, Wolfgang Ketterle
Categories: cond-mat.quant-gas
Comments: 5 pages, 3 figures
\\
We demonstrate spin gradient thermometry, a new general method of measuring
the temperature of ultracold atoms in optical lattices. We realize a mixture of
spins separated by a magnetic field gradient. Measurement of the width of the
transition layer between the two spin domains serves as a new method of
thermometry which is observed to work over a broad range of lattice depths and
temperatures, including in the Mott insulator regime. We demonstrate the
thermometry in a system of ultracold rubidium atoms. The lowest measured
temperature is 1 nK, indicating that the system has reached the quantum regime,
where insulating shells are separated by superfluid layers.
\\ ( http://arxiv.org/abs/0908.3046 , 64kb)
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arXiv:0908.3052
Date: Fri, 21 Aug 2009 04:40:32 GMT (441kb)
Title: Quantitative test of mean-field description of a trapped two-dimensional
Bose gas
Authors: R. N. Bisset and P. B. Blakie
Categories: cond-mat.quant-gas
Comments: 5 pages, 2 figures, 1 table
\\
We investigate the accuracy of two mean-field theories of the trapped
two-dimensional Bose gas at predicting transition region properties by
comparison to non-perturbative c-field calculations. To make these comparisons
we examine the density profiles and the predictions for the
Berezinskii-Kosterlitz-Thouless superfluid transition temperature over a
parameter range in which the degree of thermal activation in the tightly
trapped direction varies considerably. These results present an important test
of these mean-field theories, and provide a characterization of their typical
accuracy.
\\ ( http://arxiv.org/abs/0908.3052 , 441kb)
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arXiv:0908.3074
Date: Fri, 21 Aug 2009 08:33:54 GMT (350kb)
Title: The BCS-BEC crossover and the disappearance of FFLO-correlations in a
spin-imbalanced, one-dimensional Fermi gas
Authors: F. Heidrich-Meisner. A.E. Feiguin, U. Schollwoeck, W. Zwerger
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 13 pages, 21 eps figures
\\
We present a numerical study of the one-dimensional BCS-BEC crossover of a
spin-imbalanced Fermi gas. The crossover is described by the Bose-Fermi
resonance model in a real space representation. Our main interest is in the
behavior of the pair correlations, which, in the BCS limit, are of the
Fulde-Ferrell-Larkin-Ovchinnikov type, while in the BEC limit, a superfluid of
diatomic molecules forms that exhibits quasi-condensation at zero momentum. We
use the density matrix renormalization group method to compute the phase
diagram as a function of the detuning of the molecular level and the
polarization. As a main result, we show that FFLO-like correlations disappear
well below full polarization close to the resonance. The critical polarization
depends on both the detuning and the filling.
\\ ( http://arxiv.org/abs/0908.3074 , 350kb)
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arXiv:0908.3110
Date: Fri, 21 Aug 2009 19:54:59 GMT (274kb)
Title: Detection of Fermi Pairing via Electromagnetically Induced Transparency
Authors: Lei Jiang, Han Pu, Weiping Zhang, and Hong Y. Ling
Categories: cond-mat.quant-gas cond-mat.other
Comments: 8 pages, 2 figures, to appear in Phys. Rev. A
\\
An optical spectroscopic method based on the principle of
electromagnetically-induced transparency (EIT) is proposed as quite a generic
probing tool that provides valuable insights into the nature of Fermi paring in
ultracold Fermi gases of two hyperfine states. This technique has the
capability of allowing spectroscopic response to be determined in a nearly
non-destructive manner and the whole spectrum may be obtained by scanning the
probe laser frequency faster than the lifetime of the sample without
re-preparing the atomic sample repeatedly. A quasiparticle picture is
constructed to facilitate a simple physical explanation of the pairing
signature in the EIT spectra.
\\ ( http://arxiv.org/abs/0908.3110 , 274kb)
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arXiv:0908.3179
Date: Fri, 21 Aug 2009 18:52:26 GMT (139kb)
Title: Ion induced density bubble in a strongly correlated one dimensional gas
Authors: J. Goold, H. Doerk-Bending, T. Calarco, Th. Busch
Categories: cond-mat.quant-gas quant-ph
Comments: 5 pages, 3 figures
\\
We consider a harmonically trapped Tonks-Girardeau gas of impenetrable bosons
in the presence of a single embedded ion, which is assumed to be tightly
confined in a RF trap. In an ultracold ion-atom collision the ion's charge
induces an electric dipole moment in the atoms which leads to an attractive
$r^{-4}$ potential at large distances. We treat the ion as a deformation of the
harmonic trap potential and model its short range interaction with the gas in
the framework of quantum defect theory. The molecular bound states of the ionic
potential are not populated due to the lack of any possible relaxation process
in the Tonks-Girardeau regime. Armed with this knowledge we calculate the
density profile of the gas in the presence of a central ionic impurity and show
that a density \textit{bubble} of the order of a micron occurs around the ion
for typical experimental parameters. From these exact results we show that an
ionic impurity in a Tonks gas can be described using a pseudopotential,
allowing for significantly easier treatment.
\\ ( http://arxiv.org/abs/0908.3179 , 139kb)
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arXiv:0908.3012
Date: Fri, 21 Aug 2009 18:53:11 GMT (2962kb)
Title: Classical phases and quantum angles in the description of interfering
Bose-Einstein condensates
Authors: W. J. Mullin and F. Lalo\"e
Categories: quant-ph
Comments: 35 pages, 22 figures
\\
The interference of two Bose-Einstein condensates, initially in Fock states,
can be described in terms of their relative phase, treated as a random unknown
variable. This phase can be understood, either as emerging from the
measurements, or preexisting to them; in the latter case, the originating
states could be phase states with unknown phases, so that an average over all
their possible values is taken. Both points of view lead to a description of
probabilities of results of experiments in terms of a phase angle, which plays
the role of a classical variable. Nevertheless, in some situations, this
description is not sufficient: another variable, which we call the "quantum
angle", emerges from the theory. This article studies various manifestations of
the quantum angle. We first introduce the quantum angle by expressing two Fock
states crossing a beam splitter in terms of phase states, and relate the
quantum angle to off-diagonal matrix elements in the phase representation. Then
we consider an experiment with two beam splitters, where two experimenters make
dichotomic measurements with two interferometers and detectors that are far
apart; the results lead to violations of the Bell-Clauser-Horne-Shimony-Holt
inequality (valid for local-realistic theories, including classical
descriptions of the phase). Finally, we discuss an experiment where particles
from each of two sources are either deviated via a beam splitter to a side
collector or proceed to the point of interference. For a given interference
result, we find "population oscillations" in the distributions of the deviated
particles, which are entirely controlled by the quantum angle. Various versions
of population oscillation experiments are discussed, with two or three
independent condensates.
\\ ( http://arxiv.org/abs/0908.3012 , 2962kb)
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arXiv:0908.2815 (*cross-listing*)
Date: Wed, 19 Aug 2009 20:20:01 GMT (40kb)
Title: Semirelativistic N-boson systems bound by attractive pair potentials
Authors: Richard L. Hall, Wolfgang Lucha
Categories: math-ph hep-ph math.MP quant-ph
Comments: 12 pages, 2 figures
Report-no: CUQM - 131; HEPHY - PUB 879/09
\\
We establish bounds on the energy of a system of N identical bosons bound by
attractive pair potentials and obeying the semirelativistic Salpeter equation.
The lower bound is provided by a `reduction', with the aid of Jacobi relative
coordinates, to a suitably scaled one-body Klein-Gordon problem. Complementary
upper energy bounds are provided by means of a Gaussian trial function.
Detailed results are presented for the exponential pair potential V(r) =
-v\exp(-r/a).
\\ ( http://arxiv.org/abs/0908.2815 , 40kb)
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arXiv:0908.3147
Date: Fri, 21 Aug 2009 15:15:06 GMT (181kb)
Title: Decoherence and Collisional Frequency Shifts of Trapped Bosons and
Fermions
Authors: Kurt Gibble
Categories: physics.atom-ph
Comments: To appear in PRL
\\
We perform exact calculations of collisional frequency shifts for several
fermions or bosons using a singlet and triplet basis for pairs of particles.
The "factor of 2 controversy" for bosons becomes clear - the factor is always
2. Decoherence is described by singlet states and they are unaffected by
spatially uniform clock fields. Spatial variations are critical, especially for
fermions which were previously thought to be immune to collision shifts. The
spatial variations lead to decoherence and a novel frequency shift that is not
proportional to the partial density of internal states.
\\ ( http://arxiv.org/abs/0908.3147 , 181kb)
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arXiv:0908.3188
Date: Fri, 21 Aug 2009 21:49:09 GMT (304kb)
Title: Quantum quenches and thermalization in one-dimensional fermionic systems
Authors: Marcos Rigol
Categories: cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el
Comments: 12 pages, 12 figures
\\
We study the dynamics and thermalization of strongly correlated fermions in
finite one-dimensional lattices after a quantum quench. Our calculations are
performed using exact diagonalization. We focus on one- and two-body
observables such as the momentum distribution function [n(k)] and the
density-density structure factor [N(k)], respectively, and study the effects of
approaching an integrable point. We show that while the relaxation dynamics and
thermalization of N(k) for fermions is very similar to the one of hardcore
bosons, the behavior of n(k) is distinctively different. The latter observable
exhibits a slower relaxation dynamics in fermionic systems. We identify the
origin of this behavior, which is related to the off-diagonal matrix elements
of n(k) in the basis of the eigenstates of the Hamiltonian. More generally, we
find that thermalization occurs far away from integrability and that it breaks
down as one approaches the integrable point.
\\ ( http://arxiv.org/abs/0908.3188 , 304kb)
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arXiv:0908.3235
Date: Mon, 24 Aug 2009 19:35:40 GMT (227kb)
Title: An atomic colour superfluid via three-body loss
Authors: A. Kantian, M. Dalmonte, S. Diehl, W. Hofstetter, P. Zoller, A. J.
Daley
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures
\\
Large three-body losses in a three-component Fermi gas confined in an optical
lattice can prevent the occupation of a lattice site by three atoms. This
effective constraint not only gives rise to a suppression of actual three-body
loss, but stabilises BCS pairing phases by suppressing the formation of trions.
We study the effects of the constraint using bosonisation and density matrix
renormalisation group techniques (DMRG). We discuss the case of lithium
experiments, and study the dissipative dynamics including loss using
time-dependent DMRG with quantum trajectories methods.
\\ ( http://arxiv.org/abs/0908.3235 , 227kb)
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arXiv:0908.3260
Date: Sat, 22 Aug 2009 15:57:34 GMT (282kb,D)
Title: Non classical velocity statistics in a turbulent atomic Bose Einstein
condensate
Authors: Angela White, Nick P. Proukakis and Carlo F. Barenghi
Categories: cond-mat.quant-gas cond-mat.other
Comments: 10 pages, 3 figures
\\
In a recent experiment Paoletti et al (Phys. Rev. Lett. 101, 154501, 2008)
monitored the motion of tracer particles in turbulent superfluid helium and
inferred that the velocity components do not obey the Gaussian statistics
observed in ordinary turbulence. Motivated by their experiment, we create a
small turbulent state in an atomic Bose-Einstein condensate, which enables us
to compute directly the velocity field, and we find similar non-classical
power-law tails. Our result thus suggests that non-Gaussian turbulent velocity
statistics describe a fundamental property of quantum fluids. We also track the
decay of the vortex tangle in the presence of the thermal cloud.
\\ ( http://arxiv.org/abs/0908.3260 , 282kb)
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arXiv:0908.3356
Date: Mon, 24 Aug 2009 03:08:35 GMT (1522kb)
Title: Quantum Information Approach to Rotating Bose-Einstein Condensate
Authors: Zhao Liu, Hongli Guo, Shu Chen and Heng Fan
Categories: cond-mat.quant-gas quant-ph
Comments: 4 pages, 6 figures
\\
We investigate the 2D weakly interacting Bose-Einstein condensate in a
rotating trap by the tools of quantum information theory. The critical
exponents of the ground state fidelity susceptibility and the correlation
length of the system are obtained for the quantum phase transition when the
frst vortex is formed. We also find the single-particle entanglement can be an
indicator of the angular momentums for some real ground states. The
single-particle entanglement of fractional quantum Hall states such as Laughlin
state and Pfaffian state is also studied.
\\ ( http://arxiv.org/abs/0908.3356 , 1522kb)
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arXiv:0908.3204
Date: Fri, 21 Aug 2009 20:42:48 GMT (23kb)
Title: Collisional decoherence of internal state superpositions in a trapped
ultracold gas
Authors: C. J. Hemming and R. V. Krems
Categories: quant-ph
Comments: 20 pages, 1 figure
\\
We analyze the temperature-dependent rate of decoherence of superpositions of
internal states of trapped molecules due to collisions with ultracold buffer
gas particles. Our analysis is applicable for an arbitrary bath/tracer particle
mass ratio. Both elastic and inelastic collisions contribute to decoherence. We
obtain an expression relating the observable decoherence rate to pairwise
scattering properties, specifically the scattering lengths and low-temperature
cross-sections. We consider the dependence on the bath/tracer particle mass
ratio for the case of light bath and heavy tracer particles. The expressions
obtained may be useful in low-temperature applications where accurate estimates
of decoherence rates are desirable. The results suggest a method for
determining the scattering lengths of atoms and molecules in different internal
states by measuring decoherence-induced damping of coherent oscillations.
\\ ( http://arxiv.org/abs/0908.3204 , 23kb)
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arXiv:0908.3483
Date: Tue, 25 Aug 2009 19:34:28 GMT (504kb,D)
Title: Non-equilibrium dynamics of interacting Fermi systems in quench
experiments
Authors: Mehrtash Babadi, David Pekker, Rajdeep Sensarma, Antoine Georges,
Eugene Demler
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 4 Pages, 2 Figs
\\
We describe the dynamics of two component non-interacting ultracold Fermions
which are initially in thermal equilibrium and undergo a rapid quench to either
the repulsive or attractive side of a Feshbach resonance. The short time
dynamics is dominated by the exponentially growing collective modes. We study
the Stoner instability and formation of ferromagnetic textures on the repulsive
side, and the pairing instability towards BCS or FFLO-like states (determined
by the population imbalance) on the attractive side. In each case, we evaluate
the growth rate of unstable modes and predict the typical lengthscale of
textures to be formed.
\\ ( http://arxiv.org/abs/0908.3483 , 504kb)
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arXiv:0908.3484
Date: Mon, 24 Aug 2009 20:01:24 GMT (95kb)
Title: Hyperfine Spin-Two (F=2) Atoms in Three-Dimensional Optical Lattices:
Phase Diagrams and Phase Transitions
Authors: Michiel Snoek, Jun Liang Song, and Fei Zhou
Categories: cond-mat.quant-gas
Comments: 10 pages, 10 figures
\\
We consider ultracold matter of spin-2 atoms in optical lattices. We derive
an effective Hamiltonian for the studies of spin ordering in Mott states and
investigate hyperfine spin correlations. Particularly, we diagonalize the
Hamiltonian in an on-site Hilbert space taking into account spin-dependent
interactions and exchange between different sites. We obtain phase diagrams and
quantum phase transitions between various magnetic phases.
\\ ( http://arxiv.org/abs/0908.3484 , 95kb)
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arXiv:0908.3547
Date: Tue, 25 Aug 2009 08:02:36 GMT (76kb)
Title: Quasiparticle excitations in Bose-Fermi mixtures
Authors: Shimul Akhanjee
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 7 pages, eps figures
\\
We analyze the excitation spectrum of a three-dimensional(3D) Bose-Fermi
mixture with tunable resonant interaction parameters. We focus on an attractive
3-particle vertex describing fermionic and bosonic atoms which can scatter to
create fermionic molecules. We demonstrate how this interaction vertex causes
the Lorentzian broadening of an $N_\psi$-fold degenerate molecular Fermi
energy. Mean field equations for a flat, wide atomic dispersion are generated
by a linked cluster expansion and within a Hartree approximation. Beyond mean
field theory, a random phase approximation (RPA) generates a correction to the
bosonic chemical potential at order $1/N_\psi$. The results are expected to be
exact in the limit of infinite degeneracy $N_\psi \to \infty$. We conjecture
that the quasiparticle features of the one level analysis of excitation spectra
apply to the case containing dispersive bands.
\\ ( http://arxiv.org/abs/0908.3547 , 76kb)
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arXiv:0908.3631
Date: Tue, 25 Aug 2009 15:21:28 GMT (900kb,D)
Title: Chiral confinement in quasirelativistic Bose-Einstein condensates
Authors: M. Merkl, A. Jacob, F. E. Zimmer, P. Ohberg and L. Santos
Categories: cond-mat.quant-gas
Comments: 4 pages
\\
In the presence of a laser-induced spin-orbit coupling an interacting ultra
cold spinor Bose-Einstein condensate may acquire a quasi-relativistic character
described by a non-linear Dirac-like equation. We show that as a result of the
spin-orbit coupling and the non-linearity the condensate may become
self-trapped, resembling the so-called chiral confinement, previously studied
in the context of the massive Thirring model. We first consider 1D geometries
where the self-confined condensates present an intriguing sinusoidal dependence
on the inter-particle interactions. We further show that multi-dimensional
chiral-confinement is also possible under appropriate feasible laser
arrangements, and discuss the properties of 2D and 3D condensates, which differ
significantly from the 1D case.
\\ ( http://arxiv.org/abs/0908.3631 , 900kb)
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arXiv:0908.3504
Date: Mon, 24 Aug 2009 21:33:27 GMT (356kb,D)
Title: Macroscopic magnetic guide for cold atoms
Authors: Alexey Tonyushkin and Mara Prentiss
Categories: physics.atom-ph physics.ins-det
\\
We demonstrate a macroscopic magnetic guide for cold atoms, and show the
results of its application to atom interferometry. This guide is based on
copper tape coils that allow the guide to be located more than a cm away from
the surface of the coils; therefore these structures can be placed outside the
vacuum chamber. Compared to a ferromagnetic guide, the new guides offer precise
control over the magnetic field. The guide utilizes symmetric geometry, where
the atoms are located symmetrically between the coils. This geometry has
provided a much lower magnetic field curvature that promises longer coherence
time for atom interferometers.
\\ ( http://arxiv.org/abs/0908.3504 , 356kb)
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arXiv:0908.2447 (*cross-listing*)
Date: Mon, 17 Aug 2009 21:16:48 GMT (62kb,D)
Title: Using Atom Interferometery to Search for New Forces
Authors: Jay G. Wacker
Categories: hep-ph physics.atom-ph
Comments: 5 pages, 2 figures
\\
Atom interferometry is a rapidly advancing field and this Letter proposes an
experiment based on existing technology that can search for new short distance
forces. With current technology it is possible to improve the sensitivity by up
to a factor of 102 and near-future advances will be able to rewrite the limits
for forces with ranges from 100 um to 1 km.
\\ ( http://arxiv.org/abs/0908.2447 , 62kb)
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arXiv:0908.3733
Date: Wed, 26 Aug 2009 06:36:36 GMT (561kb)
Title: Induced interactions and the superfluid transition temperature in a
three-component Fermi gas
Authors: J.-P. Martikainen, J. Kinnunen, P. Torma, C. J. Pethick
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 4 pages, 5 figures
Report-no: NORDITA-2009-52
\\
We study many-body contributions to the effective interaction between
fermions in a three-component Fermi mixture. We find that effective
interactions between two components induced by the third component can lead to
a phase diagram different from that predicted if interactions with the third
component are neglected. As a result, in a confining potential a superfluid
shell structure can arise even for equal populations of the components. We
compute the critical temperature for the BCS transition in a three-component
6Li mixture and find that the result can deviate strongly from the reduction of
T_c by a factor 2.22 predicted for a weakly interacting two-component system.
\\ ( http://arxiv.org/abs/0908.3733 , 561kb)
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arXiv:0908.3790
Date: Wed, 26 Aug 2009 10:42:43 GMT (240kb)
Title: Modification of energy shifts of atoms by the presence of a boundary in
a thermal bath and the Casimir-Polder force
Authors: Zhiying Zhu, Hongwei Yu
Categories: quant-ph physics.atom-ph
Comments: 29 pages, 3 figures
Journal-ref: Phys. Rev. A 79, 032902 (2009
DOI: 10.1103/PhysRevA.79.032902
\\
We study the modification by the presence of a plane wall of energy level
shifts of two-level atoms which are in multipolar coupling with quantized
electromagnetic fields in a thermal bath in a formalism which separates the
contributions of thermal fluctuations and radiation reaction and allows a
distinct treatment to atoms in the ground and excited states. The position
dependent energy shifts give rise to an induced force acting on the atoms. We
are able to identify three different regimes where the force shows distinct
features and examine, in all regimes, the behaviors of this force in both the
low temperature limit and the high temperature limit for both the ground state
and excited state atoms, thus providing some physical insights into the
atom-wall interaction at finite temperature. In particular, we show that both
the magnitude and the direction of the force acting on an atom may have a clear
dependence on atomic the polarization directions. In certain cases, a change of
relative ratio of polarizations in different directions may result in a change
of direction of the force.
\\ ( http://arxiv.org/abs/0908.3790 , 240kb)
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arXiv:0908.3791
Date: Wed, 26 Aug 2009 13:12:39 GMT (185kb)
Title: Observation of Electromagnetically Induced Transparency and Slow Light
in the Dark State - Bright State Basis of CPT
Authors: T. Laupr\^etre (LAC), J. Ruggiero (LAC), R. Ghosh (JNU), F. Bretenaker
(LAC), F. Goldfarb (LAC)
Categories: quant-ph
\\
Electromagnetically induced transparency (EIT) is observed in a three-level
system composed of an excited state and two coherent superpositions of the two
ground-state levels. This peculiar ground state basis is composed of the
so-called bright and dark states of the same atomic system in a standard
coherent population trapping configuration. The characteristics of EIT, namely,
width of the transmission window and reduced group velocity of light, in this
unusual basis, are theoretically and experimentally investigated and are shown
to be essentially identical to those of standard EIT in the same system.
\\ ( http://arxiv.org/abs/0908.3791 , 185kb)
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arXiv:0908.3867
Date: Wed, 26 Aug 2009 17:12:34 GMT (43kb,D)
Title: Double humped states in the nonlinear Schroedinger equation with a
random potential
Authors: Hagar Veksler, Yevgeny Krivolapov and Shmuel Fishman
Categories: quant-ph
Comments: 10 pages, 3 figures
\\
The role of double humped states in spreading of wave packets for the
nonlinear Schroedinger equation (NLSE) with a random potential is explored and
the spreading mechanism is unraveled. Comparison with an NLSE with a
double-well potential is made. There are two independent affects of the
nonlinearity on the double humped states for the NLSE: coupling to other states
and destruction. The interplay between these effects is discussed.
\\ ( http://arxiv.org/abs/0908.3867 , 43kb)
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arXiv:0908.3919
Date: Thu, 27 Aug 2009 01:02:29 GMT (31kb)
Title: Particle-Hole Asymmetry and Brightening of Solitons in A Strongly
Repulsive BEC
Authors: Radha Balakrishnan, Indubala I. Satija and Charles W. Clark
Categories: cond-mat.quant-gas
\\
We study solitary wave propagation in the condensate of a system of hard-core
bosons with nearest neighbor interactions. For this strongly repulsive system,
the evolution equation for the condensate order parameter obtained using spin
coherent state averages is different from the usual Gross-Pitaevskii equation
(GPE). The system is found to support two kinds of solitons when there is a
particle-hole imbalance: a gray soliton that dies out as the velocity
approaches the Bogoliubov sound velocity, and a new type of soliton which
brightens and persists all the way up to the sound velocity, transforming into
a periodic wave train at supersonic speed. Analogous to GPE soliton, the
energy-momentum dispersion for both the solitons is characterized by Lieb II
modes.
\\ ( http://arxiv.org/abs/0908.3919 , 31kb)
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\\
arXiv:0908.3686 (*cross-listing*)
Date: Tue, 25 Aug 2009 20:50:33 GMT (225kb)
Title: Hot Topics in Cold Gases
Authors: Robert Seiringer
Categories: math-ph cond-mat.quant-gas math.MP
Comments: Plenary lecture given at the XVI International Congress on
Mathematical Physics, Prague, August 3-8, 2009
\\
Since the first experimental realization of Bose-Einstein condensation in
cold atomic gases in 1995 there has been a surge of activity in this field.
Ingenious experiments have allowed us to probe matter close to zero temperature
and reveal some of the fascinating effects quantum mechanics has bestowed on
nature. It is a challenge for mathematical physicists to understand these
various phenomena from first principles, that is, starting from the underlying
many-body Schr\"odinger equation. Recent progress in this direction concerns
mainly equilibrium properties of dilute, cold quantum gases. We shall explain
some of the results in this article, and describe the mathematics involved in
understanding these phenomena. Topics include the ground state energy and the
free energy at positive temperature, the effect of interparticle interaction on
the critical temperature for Bose-Einstein condensation, as well as the
occurrence of superfluidity and quantized vortices in rapidly rotating gases.
\\ ( http://arxiv.org/abs/0908.3686 , 225kb)
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\\
arXiv:0908.3952
Date: Thu, 27 Aug 2009 08:36:25 GMT (79kb)
Title: Open system effects on slow light and electromagnetically induced
transparency
Authors: Jonas Tidstr\"om, Marie Ericsson, Erik Sj\"oqvist, L. Mauritz
Andersson
Categories: quant-ph
\\
The interaction of a three-level $\Lambda$-system with a Markovian
environment is analyzed. A coherence vector formalism is used and a vector form
of the Lindblad equation is derived. Depolarization, dephasing, and different
amplitude damping channels acting on the subspace of the ground states of the
$\Lambda$-system are investigated. Analytic expressions of the concomitant
optical susceptibility are given in the limit of a small probe field and a
strong control field, and we analyze how the different channels influence the
optical response. For a given group velocity, the absorption depends
non-trivially on the type of open system interaction and even gain can be
obtained.
\\ ( http://arxiv.org/abs/0908.3952 , 79kb)
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The replacements:
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\\
arXiv:0903.5265
replaced with revised version Fri, 21 Aug 2009 09:35:17 GMT (899kb)
Title: Antiferromagnetic Order of Repulsively Interacting Fermions on Optical
lattices
Authors: Tobias Gottwald, Peter van Dongen
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0903.5265 , 899kb)
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\\
arXiv:0904.0238
replaced with revised version Mon, 24 Aug 2009 15:17:28 GMT (89kb)
Title: Bragg spectroscopy for measuring Casimir-Polder interactions with
Bose-Einstein condensates above corrugated surfaces
Authors: Gustavo A. Moreno, Diego A. R. Dalvit, Esteban Calzetta
Categories: quant-ph
Comments: revised version
\\ ( http://arxiv.org/abs/0904.0238 , 89kb)
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\\
arXiv:0903.3054
replaced with revised version Tue, 25 Aug 2009 07:07:40 GMT (107kb)
Title: Large violation of Wiedemann Franz law in Luttinger liquids
Authors: Arti Garg, David Rasch, Efrat Shimshoni, Achim Rosch
Categories: cond-mat.str-el
Comments: Added reference
Journal-ref: Phys. Rev. Lett. 103, 096402 (2009)
DOI: 10.1103/PhysRevLett.103.096402
\\ ( http://arxiv.org/abs/0903.3054 , 107kb)
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\\
arXiv:0907.2245 (*cross-listing*)
replaced with revised version Wed, 26 Aug 2009 15:40:02 GMT (366kb,D)
Title: Many-body treatment of the collisional frequency shift in fermionic
atoms
Authors: A. M. Rey, A. V. Gorshkov, C. Rubbo
Categories: physics.atom-ph cond-mat.quant-gas cond-mat.str-el quant-ph
Comments: 5 pages, 3 figures. V2: added 1 reference
\\ ( http://arxiv.org/abs/0907.2245 , 366kb)
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\\
arXiv:0906.0014
replaced with revised version Wed, 26 Aug 2009 23:37:01 GMT (520kb)
Title: Renormalization Group for Mixed Fermion-Boson Systems
Authors: Seiji J. Yamamoto and Qimiao Si
Categories: cond-mat.str-el
Comments: (v2) a few points made clearer and some types corrected
\\ ( http://arxiv.org/abs/0906.0014 , 520kb)
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Till next time,
Matt.
--
=========================================================================
Dr M. J. Davis, Associate Professor in Physics
School of Mathematics and Physics, ph : +61 7 334 69824
The University of Queensland, fax : +61 7 336 51242
Brisbane, QLD 4072, mdavis_at_physics.uq.edu.au
Australia. www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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