[Matts-arxiv] Matt's arXiv selection: week ending 24 July 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Sat, 05 Sep 2009 20:22:05 +1000

Dear subscribers,

The bus is still going... it looks like four weeks worth is going to be the
limit for today. This week was compiled by Andy Ferris. There are a whopping
38 new preprints and 16 replacements.

Date: Thu, 16 Jul 2009 20:13:00 GMT (340kb)

Title: Dynamical Mean Field Theory for the Bose-Hubbard Model
Authors: Wen-Jun Hu and Ning-Hua Tong
Categories: cond-mat.quant-gas cond-mat.other
Comments: 11 pages, 8 figures
   The dynamical mean field theory (DMFT), which is successful in the study of
strongly correlated fermions, was recently extended to boson systems [Phys.
Rev. B {\textbf 77}, 235106 (2008)]. In this paper, we employ the bosonic DMFT
to study the Bose-Hubbard model which describes on-site interacting bosons in a
lattice. Using exact diagonalization as the impurity solver, we get the DMFT
solutions for the Green's function, the occupation density, as well as the
condensate fraction on a Bethe lattice. Various phases are identified: the Mott
insulator, the Bose-Einstein condensed (BEC) phase, and the normal phase. At
finite temperatures, we obtain the crossover between the Mott-like regime and
the normal phase, as well as the BEC-to-normal phase transition. Phase diagrams
on the $\mu/U-\tilde{t}/U$ plane and on the $T/U-\tilde{t}/U$ plane are
produced ($\tilde{t}$ is the scaled hopping amplitude). We compare our results
with the previous ones, and discuss the implication of these results to
\\ ( http://arxiv.org/abs/0907.2928 , 340kb)
Date: Thu, 16 Jul 2009 22:39:50 GMT (230kb,D)

Title: Simulating Stochastic Dynamics Using Large Time Steps
Authors: O. Corradini, P. Faccioli and H. Orland
Categories: cond-mat.soft cond-mat.stat-mech
Comments: 17 pager, 7 figures
   We present a novel approach to investigate the long-time stochastic dynamics
of multi-dimensional classical systems, in contact with a heat-bath. When the
potential energy landscape is rugged, the kinetics displays a decoupling of
short and long time scales and both
   Molecular Dynamics (MD) or Monte Carlo (MC) simulations are generally
inefficient. Using a field theoretic approach, we perform analytically the
average over the short-time stochastic fluctuations. This way, we obtain an
effective theory, which generates the same long-time dynamics of the original
theory, but has a lower time resolution power. Such an approach is used to
develop an improved version of the MC algorithm, which is particularly suitable
to investigate the dynamics of rare conformational transitions. In the specific
case of molecular systems at room temperature, we show that elementary
integration time steps used to simulate the effective theory can be chosen a
factor ~100 larger than those used in the original theory. Our results are
illustrated and tested on a simple system, characterized by a rugged energy
\\ ( http://arxiv.org/abs/0907.2948 , 230kb)
Date: Fri, 17 Jul 2009 11:58:48 GMT (619kb)

Title: Textures and non-Abelian vortices in atomic d-wave paired Fermi
Authors: H. M. Adachi, Y. Tsutsumi, J. A. M. Huhtam\"aki, K. Machida
Categories: cond-mat.supr-con cond-mat.quant-gas
Comments: 5 pages, 4 figures
   We report on fundamental properties of superfluids with d-wave pairing
symmetry. We consider neutral atomic Fermi gases in a harmonic trap, the
pairing being produced by a Feshbach resonance via a d-wave interaction
channel. A Ginzburg-Landau (GL) functional is constructed which is symmetry
constrained for five component order parameters (OP). We find OP textures in
the cyclic phase and stability conditions for a non-Abelian fractional
1/3-vortex under rotation. It is proposed how to create the intriguing
1/3-vortex experimentally in atomic gases via optical means.
\\ ( http://arxiv.org/abs/0907.2972 , 619kb)
Date: Fri, 17 Jul 2009 08:20:54 GMT (159kb)

Title: Spin drag in noncondensed Bose gases
Authors: R.A. Duine, H.T.C. Stoof
Categories: cond-mat.quant-gas
   We show how time-dependent magnetic fields lead to spin motive forces and
spin drag in a spinor Bose gas. We propose to observe these effects in a
toroidal trap and analyze this particular proposal in some detail. In the
linear-response regime we define a transport coefficient that is analogous to
the usual drag resistivity in electron bilayer systems. Due to Bose enhancement
of atom-atom scattering, this coefficient strongly increases as temperature is
lowered. We also investigate the effects of heating.
\\ ( http://arxiv.org/abs/0907.3017 , 159kb)
Date: Fri, 17 Jul 2009 09:03:47 GMT (401kb)

Title: Numerical approaches to time evolution of complex quantum systems
Authors: Holger Fehske, Jens Schleede, Gerald Schubert, Gerhard Wellein,
   Vladimir S. Filinov, and Alan R. Bishop
Categories: cond-mat.str-el
Comments: 8 pages, 3 figures
Journal-ref: Phys. Lett. A 373, 2182 (2009)
   We examine several numerical techniques for the calculation of the dynamics
of quantum systems. In particular, we single out an iterative method which is
based on expanding the time evolution operator into a finite series of
Chebyshev polynomials. The Chebyshev approach benefits from two advantages over
the standard time-integration Crank-Nicholson scheme: speedup and efficiency.
Potential competitors are semiclassical methods such as the Wigner-Moyal or
quantum tomographic approaches. We outline the basic concepts of these
techniques and benchmark their performance against the Chebyshev approach by
monitoring the time evolution of a Gaussian wave packet in restricted
one-dimensional (1D) geometries. Thereby the focus is on tunnelling processes
and the motion in anharmonic potentials. Finally we apply the prominent
Chebyshev technique to two highly non-trivial problems of current interest: (i)
the injection of a particle in a disordered 2D graphene nanoribbon and (ii) the
spatiotemporal evolution of polaron states in finite quantum systems. Here,
depending on the disorder/electron-phonon coupling strength and the device
dimensions, we observe transmission or localisation of the matter wave.
\\ ( http://arxiv.org/abs/0907.3022 , 401kb)
Date: Fri, 17 Jul 2009 09:57:28 GMT (588kb)

Title: Collective Oscillations of an Imbalanced Fermi Gas: Axial Compression
   Modes and Polaron Effective Mass
Authors: Sylvain Nascimbene (LKB - Lhomond), Nir Navon (LKB - Lhomond), Kaijun
   Jiang (LKB - Lhomond), Leticia Tarruell (ETH), Martin Teichmann
   (Max-Born-Institut), Jason Mckeever (IOS), Fr\'ed\'eric Chevy (LKB -
   Lhomond), Christophe Salomon (LKB - Lhomond)
Categories: cond-mat.other
Comments: 4 pages, 4 figures, submitted to PRL
   We investigate the low-lying compression modes of a unitary Fermi gas with
imbalanced spin populations. For low polarization, the strong coupling between
the two spin components leads to a hydrodynamic behavior of the cloud. For
large population imbalance we observe a decoupling of the oscillations of the
two spin components, giving access to the effective mass of the Fermi polaron,
a quasi-particle composed of an impurity dressed by particle-hole pair
excitations in a surrounding Fermi sea. We find $m^*/m=1.17(10)$, in agreement
with the most recent theoretical predictions.
\\ ( http://arxiv.org/abs/0907.3032 , 588kb)
Date: Fri, 17 Jul 2009 13:46:18 GMT (122kb)

Title: Core sizes and dynamic instabilities of giant vortices in dilute
   Bose-Einstein condensates
Authors: Pekko Kuopanportti, Emil Lundh, Jukka Huhtam\"aki, Ville Pietil\"a,
   Mikko M\"ott\"onen
Categories: cond-mat.quant-gas
Comments: 8 pages, 6 figures
   Motivated by recent demonstration of cyclic addition of quantized vorticity
into a Bose-Einstein condensate, the vortex pump, we study dynamic
instabilities and core sizes of giant vortices. The core size is found to
increase roughly as a square-root function of the quantum number of the vortex,
whereas the strength of the dynamic instability either saturates to a fairly
low value or increases extremely slowly for large quantum numbers. Our studies
suggest that giant vortices of very high angular momenta may be achieved by
gradually increasing the operation frequency of the vortex pump.
\\ ( http://arxiv.org/abs/0907.3077 , 122kb)
Date: Fri, 17 Jul 2009 18:48:08 GMT (37kb)

Title: Stable Topological Superfluid Phase of Ultracold Polar Fermionic
Authors: N. R. Cooper and G. V. Shlyapnikov
Categories: cond-mat.quant-gas cond-mat.str-el
   We show that single-component fermionic polar molecules confined to a 2D
geometry and dressed by a microwave field, may acquire an attractive $1/r3$
dipole-dipole interaction leading to superfluid p-wave pairing at sufficiently
low temperatures even in the BCS regime. The emerging state is the topological
$p_x+ip_y$ phase promising for topologically protected quantum information
processing. The main decay channel is via collisional transitions to dressed
states with lower energies and is rather slow, setting a lifetime of the order
of seconds at 2D densities $\sim 108$ cm$^{-2}$.
\\ ( http://arxiv.org/abs/0907.3080 , 37kb)
Date: Fri, 17 Jul 2009 16:01:06 GMT (222kb,D)

Title: Second Josephson oscillations
Authors: M. P. Strzys and J. R. Anglin
Categories: cond-mat.quant-gas
   As a model for mesoscopic quantum systems in thermal contact, we consider a
four-mode Bose-Hubbard model with two greatly differing tunneling rates. By a
series of Holstein-Primakoff transformations we show that the low-frequency
dynamics of this system consists in general of two slow Josephson oscillations,
rather than the single slow mode predicted by linear Bogoliubov theory. We
identify the second slow Josephson oscillation as a heat exchange mode
analogous to second sound.
\\ ( http://arxiv.org/abs/0907.3096 , 222kb)
Date: Fri, 17 Jul 2009 19:22:30 GMT (54kb)

Title: Dynamical delocalization of Majorana edge states by sweeping across a
   quantum critical point
Authors: A. Bermudez, L. Amico, and M. A. Martin-Delgado
Categories: cond-mat.str-el
Comments: Submitted to the Special Issue on "Dynamics and Thermalization in
   Isolated Quantum Many-Body Systems" in New Journal of Physics. Editors:M.
   Cazalilla, M. Rigol
   We study the adiabatic dynamics of Majorana fermions across a quantum phase
transition. We show that the Kibble-Zurek scaling, which describes the density
of bulk defects produced during the critical point crossing, is not valid for
edge Majorana fermions. Therefore, the dynamics governing an edge state quench
is nonuniversal and depends on the topological features of the system. Besides,
we show that the localization of Majorana fermions is a necessary ingredient to
guaranty robustness against defect production.
\\ ( http://arxiv.org/abs/0907.3134 , 54kb)
Date: Fri, 22 Jun 2007 09:43:14 GMT (16kb)

Title: Trapped Bose gases with large positive scattering length
Authors: M. Th{\o}gersen, D.V. Fedorov, and A.S. Jensen
Categories: quant-ph cond-mat.quant-gas
Journal-ref: EPL 79 (2007) 40002
DOI: 10.1209/0295-5075/79/40002
   We calculate the energy and the condensate fraction of a system of trapped
bosons interacting via a short-range two-body potential with positive
scattering length. The potential is attractive and has a two-body bound state.
When the scattering length is small compared to the trap length the system is
model independent: all potential models -- attractive, repulsive and zero-range
-- provide similar results. When the scattering length is large the attractive
model differs qualitatively from the repulsive and zero-range models. In this
regime the system with attractive potential becomes independent of the
scattering length, with both the energy and the condensate fraction converging
towards finite constants.
\\ ( http://arxiv.org/abs/0706.3300 , 16kb)
Date: Tue, 24 Jun 2008 09:39:27 GMT (22kb)

Title: N-body Efimov states of trapped bosons
Authors: M. Th{\o}gersen, D. V. Fedorov, A. S. Jensen
Categories: physics.atom-ph cond-mat.quant-gas quant-ph
Journal-ref: Europhys. Lett., 83 (2008) 30012
DOI: 10.1209/0295-5075/83/30012
   We demonstrate the possibility of existence of meta-stable N-body Efimov
states in trapped Bose systems with large scattering length. We calculate
spectra of trapped systems of N=3,4,5,6, and 7 bosons using a stochastic
variational method with a restricted correlated Gaussian basis. For each system
the calculations reveal a series of Efimov states where the energy and the
r.m.s. radius exhibit the characteristic exponential dependence upon the state
number. We also estimate the contribution of these states to the recombination
rate of Bose-Einstein condensates.
\\ ( http://arxiv.org/abs/0806.3839 , 22kb)
Date: Fri, 17 Jul 2009 06:50:45 GMT (337kb)

Title: Dynamics of entanglement in a two-mode nonlinear Jaynes-Cummings mode
Authors: A B M Ahmed and S Sivakumar
Categories: quant-ph
Comments: 26 pages;9 figures
   Dynamics of entanglement due to intensity-dependent interaction between a
two-level atom and a single-mode electromagnetic field in a Kerr medium is
studied. The form of the interaction is such that the Hamiltonian evolution is
exactly solvable. The Hamiltonian is shown to be a deformed Jaynes-Cummings
model admitting a closed, symmetric algebra. Dynamics of population inversion
and atom-field entanglement are studied taking the initial state of the field
to be either a coherent state or a squeezed vacuum. Analysis is extended to the
case of a two-mode cavity field interacting with a two-level atom. For the
two-mode case, the initial field is a pair coherent state or a two-mode
squeezed vacuum. Effects due to nonlinearity, intensity-dependent interaction
and detuning on the dynamics are discussed and compared with those of the
single-mode case.
\\ ( http://arxiv.org/abs/0907.2992 , 337kb)
Date: Mon, 13 Jul 2009 16:04:36 GMT (463kb)

Title: Functional renormalization group approach to the BCS-BEC crossover
Authors: S. Diehl, S. Floerchinger, H. Gies, J. M. Pawlowski, C. Wetterich
Categories: cond-mat.quant-gas hep-th quant-ph
Comments: 28 pages, 12 figures
   The phase transition to superfluidity and the BCS-BEC crossover for an
ultracold gas of fermionic atoms is discussed within a functional
renormalization group approach. Non-perturbative flow equations, based on an
exact renormalization group equation, describe the scale dependence of the
flowing or average action. They interpolate continuously from the microphysics
at atomic or molecular distance scales to the macroscopic physics at much
larger length scales, as given by the interparticle distance, the correlation
length, or the size of the experimental probe. We discuss the phase diagram as
a function of the scattering length and the temperature and compute the gap,
the correlation length and the scattering length for molecules. Close to the
critical temperature, we find the expected universal behavior. Our approach
allows for a description of the few-body physics (scattering and molecular
binding) and the many-body physics within the same formalism.
\\ ( http://arxiv.org/abs/0907.2193 , 463kb)
Date: Sat, 18 Jul 2009 01:19:31 GMT (594kb)

Title: Solitons in Tonks-Girardeau gas with dipolar interactions
Authors: B. B. Baizakov, F. Kh. Abdullaev, B. A. Malomed, M. Salerno
Categories: cond-mat.quant-gas
Comments: 15 pages, 8 figures, accepted by J. Phys. B: At. Mol. Opt. Phys
   The existence of bright solitons in the model of the Tonks-Girardeau (TG) gas
with dipole-dipole (DD) interactions is reported. The governing equation is
taken as the quintic nonlinear Schr\"{o}dinger equation (NLSE) with the
nonlocal cubic term accounting for the DD attraction. In different regions of
the parameter space (the dipole moment and atom number), matter-wave solitons
feature flat-top or compacton-like shapes. For the flat-top states, the NLSE
with the local cubic-quintic (CQ) nonlinearity is shown to be a good
approximation. Specific dynamical effects are studied assuming that the
strength of the DD interactions is ramped up or drops to zero. Generation of
dark-soliton pairs in the gas shrinking under the action of the intensifying DD
attraction is observed. Dark solitons exhibit the particle-like collision
behavior. Peculiarities of dipole solitons in the TG gas are highlighted by
comparison with the NLSE including the local CQ terms. Collisions between the
solitons are studied too. In many cases, the collisions result in merger of the
solitons into a breather, due to strong attraction between them.
\\ ( http://arxiv.org/abs/0907.3172 , 594kb)
Date: Sat, 18 Jul 2009 10:02:03 GMT (132kb)

Title: Analytical theory of the dressed bound state in highly polarized Fermi
Authors: R. Combescot, S. Giraud and X. Leyronas
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 5 pages, 3 figures
   We present an analytical treatment of a single \down atom within a Fermi sea
of \up atoms, when the interaction is strong enough to produce a bound state,
dressed by the Fermi sea. Our method makes use of a diagrammatic analysis, with
the involved diagrams taking only into account at most two particle-hole pairs
excitations. The agreement with existing Monte-Carlo results is excellent. In
the BEC limit our equation reduces exactly to the Skorniakov and
Ter-Martirosian equation. We present results when \up and \down atoms have
different masses, which is of interest for experiments in progress.
\\ ( http://arxiv.org/abs/0907.3197 , 132kb)
Date: Sat, 18 Jul 2009 10:08:46 GMT (20kb)

Title: Analytic thermodynamics and thermometry of Gaudin-Yang Fermi gases
Authors: Erhai Zhao, Xi-Wen Guan, W. Vincent Liu, M. T. Batchelor, Masaki
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 4 pages, 2 figures
   We study the thermodynamics of a one-dimensional attractive Fermi gas (the
Gaudin-Yang model) with spin imbalance. The infinite number of coupled
thermodynamic Bethe ansatz equations are analytically reduced to a simple,
powerful set of four algebraic equations. The simplified equations become
universal and exact in the experimental regime of strong interaction and
relatively low temperature. Using the new formulation, we discuss the
qualitative features of finite-temperature crossover and make quantitative
predictions on the density profiles in traps. We propose a practical two-stage
scheme to achieve accurate thermometry for a trapped spin-imbalanced Fermi gas.
\\ ( http://arxiv.org/abs/0907.3198 , 20kb)
Date: Sat, 18 Jul 2009 11:06:46 GMT (58kb)

Title: Dynamics after a sweep through a quantum critical point
Authors: Frank Pollmann, Subroto Mukerjee, Andrew G. Green, Joel E. Moore
Categories: cond-mat.str-el
Comments: 4 pages, 4 figures
   The coherent quantum evolution of a one-dimensional many-particle system
after sweeping the Hamiltonian through a critical point is studied using a
generalized quantum Ising model containing both integrable and non-integrable
regimes. It is known from previous work that universal power laws appear in
such quantities as the mean number of excitations created by the sweep. Several
other phenomena are found that are not reflected by such averages: there are
two scaling regimes of the entanglement entropy and a relaxation that is
power-law rather than exponential.% as in the case of a sudden quench. The
final state of evolution after the quench is not well characterized by any
effective temperature, and the Loschmidt echo converges algebraically to a
constant for long times, with cusplike singularities in the integrable case
that are dynamically broadened by nonintegrable perturbations.
\\ ( http://arxiv.org/abs/0907.3206 , 58kb)
Date: Sun, 19 Jul 2009 20:15:46 GMT (9kb)

Title: Exact bosonization for an interacting Fermi gas in arbitrary dimensions
Authors: K.B. Efetov, C. Pepin, H. Meier
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 4 pages, no figures
   We present an exact mapping of models of interacting fermions onto boson
models. The bosons correspond to collective excitations in the initial
fermionic models. This bosonization is applicable in any dimension and for any
interaction between fermions. We show schematically how the mapping can be used
for Monte Carlo calculations and argue that it should be free from the sign
problem. Introducing superfields we derive a field theory that may serve as a
new way of analytical study.
\\ ( http://arxiv.org/abs/0907.3243 , 9kb)
Date: Mon, 20 Jul 2009 10:18:34 GMT (212kb)

Title: Detection of coherent superpositions of phase states by full counting
   statistics in a Bose Josephson junction
Authors: Giulia Ferrini and Anna Minguzzi and Frank W.J.Hekking
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures
   For a Bose-Josephson junction realized with a double-well potential we
propose a strategy to observe the coherent superpositions of phase states
occurring during the time evolution after a sudden rise of the barrier
separating the two wells. We show that their phase content can be obtained by
the full-counting statistics of the spin-boson operators characterizing the
junction, which could be mapped out by repeated measurements of the population
imbalance after rotation of the state. This measurement can distinguish between
coherent superpositions and incoherent mixtures, and can be used for a
two-dimensional, tomographic reconstruction of the phase content of the state.
\\ ( http://arxiv.org/abs/0907.3365 , 212kb)
Date: Mon, 20 Jul 2009 14:47:13 GMT (91kb)

Title: Parametric amplification of vacuum fluctuations in a spinor condensate
Authors: C. Klempt, O. Topic, G. Gebreyesus, M. Scherer, T. Henninger, P.
   Hyllus, W. Ertmer, L. Santos, J.J. Arlt
Categories: cond-mat.quant-gas
Comments: 5 pages, 4 figures
   Parametric amplification of vacuum fluctuations is crucial in modern quantum
optics, enabling the creation of squeezing and entanglement. We demonstrate the
parametric amplification of vacuum fluctuations for matter waves using a spinor
F=2 Rb-87 condensate. Interatomic interactions lead to correlated pair creation
in the m_F= ± 1 states from an initial unstable m_F=0 condensate, which acts
as a vacuum for m_F unequal 0. Although this pair creation from a pure m_F=0
condensate is ideally triggered by vacuum fluctuations, unavoidable spurious
initial m_F= ± 1 atoms induce a classical seed which may become the dominant
triggering mechanism. We show that pair creation is insensitive to a classical
seed for sufficiently large magnetic fields, demonstrating the dominant role of
vacuum fluctuations. The presented system thus provides a direct path towards
the generation of non-classical states of matter on the basis of spinor
\\ ( http://arxiv.org/abs/0907.3413 , 91kb)
Date: Mon, 20 Jul 2009 10:32:43 GMT (10kb)

Title: Number operator-annihilation operator uncertainty as an alternative of
   the number-phase uncertainty relation
Authors: Inigo Urizar Lanz, Geza Toth
Categories: quant-ph
Comments: 3 pages including 1 figure, revtex4
   We consider the number operator-annihilation operator uncertainty as a well
behaved alternative of the number-phase uncertainty relation, and examine its
properties. We find a formulation in which the bound on the product of
uncertainties depends on the expectation value of the particle number. Thus,
while the bound is not a constant, it is a quantity that can be easily
controlled and is even conserved in some systems. We propose several setups for
experimental verification.
\\ ( http://arxiv.org/abs/0907.3147 , 10kb)
Date: Sat, 18 Jul 2009 12:01:01 GMT (2224kb)

Title: Measuring atomic NOON-states and using them to make precision
Authors: David W. Hallwood, Adam Stokes, Jessica J. Cooper and Jacob Dunningham
Categories: quant-ph
Comments: 14 preprint pages, 7 figures
   A scheme for creating NOON-states of the quasi-momentum of ultra-cold atoms
has recently been proposed [New J. Phys. 8, 180 (2006)]. This was achieved by
trapping the atoms in an optical lattice in a ring configuration and rotating
the potential at a rate equal to half a quantum of angular momentum . In this
paper we present a scheme for confirming that a NOON-state has indeed been
created. This is achieved by spectroscopically mapping out the anti-crossing
between the ground and first excited levels by modulating the rate at which the
potential is rotated. Finally we show how the NOON-state can be used to make
precision measurements of rotation.
\\ ( http://arxiv.org/abs/0907.3213 , 2224kb)
Date: Tue, 21 Jul 2009 16:00:22 GMT (123kb)

Title: Localization of a Bose-Einstein condensate in a bichromatic optical
Authors: S. K. Adhikari and L. Salasnich
Categories: cond-mat.quant-gas
Comments: 8 pages
   By direct numerical simulation of the time-dependent Gross-Pitaevskii
equation we study different aspects of the localization of a non-interacting
ideal Bose-Einstein condensate (BEC) in a one-dimensional bichromatic
quasi-periodic optical-lattice potential. Such a quasi-periodic potential, used
in a recent experiment on the localization of a BEC [Roati et al., Nature 453,
895 (2008)], can be formed by the superposition of two standing-wave polarized
laser beams with different wavelengths. We investigate the effect of the
variation of optical amplitudes and wavelengths on the localization of a
non-interacting BEC. We also simulate the non-linear dynamics when a
harmonically trapped BEC is suddenly released into a quasi-periodic potential,
{as done experimentally in a laser speckle potential [Billy et al., Nature 453,
891 (2008)]$ We finally study the destruction of the localization in an
interacting BEC due to the repulsion generated by a positive scattering length
between the bosonic atoms.
\\ ( http://arxiv.org/abs/0907.3498 , 123kb)
Date: Mon, 20 Jul 2009 22:29:24 GMT (488kb,D)

Title: Analysis of Kapitza-Dirac diffraction patterns beyond the Raman-Nath
Authors: Bryce Gadway, Daniel Pertot, Rene Reimann, Martin G. Cohen, Dominik
Categories: cond-mat.quant-gas
   We study Kapitza-Dirac diffraction of a Bose-Einstein condensate from a
standing light wave for a square pulse with variable pulse length but constant
pulse area. We find that for sufficiently weak pulses, the usual analytical
short-pulse prediction for the Raman-Nath regime continues to hold for longer
times, albeit with a reduction of the apparent modulation depth of the standing
wave. We quantitatively relate this effect to the Fourier width of the pulse,
and draw analogies to the Rabi dynamics of a coupled two-state system. Our
findings, combined with numerical modeling for stronger pulses, are of
practical interest for the calibration of optical lattices in ultracold atomic
\\ ( http://arxiv.org/abs/0907.3507 , 488kb)
Date: Tue, 21 Jul 2009 05:43:40 GMT (32kb)

Title: Supersolidity in a Bose-Holstein model
Authors: Sanjoy Datta and Sudhakar Yarlagadda
Categories: cond-mat.str-el cond-mat.supr-con
Report-no: NSF-KITP-09-118
   We derive an effective d-dimensional Hamiltonian for a system of
hard-core-bosons coupled to optical phonons in a lattice. At non-half-fillings,
a superfluid-supersolid transition occurs at intermediate boson-phonon
couplings, while at strong-couplings the system phase separates. We demonstrate
explicitly that the presence of next-nearest-neighbor hopping and
nearest-neighbor repulsion leads to supersolidity. Thus we present a
microscopic mechanism for the homogeneous coexistence of charge-density-wave
and superfluid orders.
\\ ( http://arxiv.org/abs/0907.3543 , 32kb)
Date: Tue, 21 Jul 2009 14:35:16 GMT (119kb)

Title: Two-Poton Correlations of Luminescence under Bose-Einstein Condensation
   of Dipolar Excitons
Authors: A.V. Gorbunov, V.B. Timofeev, D.A. Demin, A.A. Dremin
Categories: cond-mat.mes-hall cond-mat.quant-gas
Comments: 6 pages, 5 figures
Journal-ref: Pis'ma v ZhETF 90 (2009) pp.156-162
   Correlations of luminescence intensity have been studied under Bose-Einstein
condensation of dipolar excitons in the temperature range of 0.45-4.2 K.
Photoexcited dipolar excitons were collected in a lateral trap in GaAs/AlGaAs
Schottky-diode heterostructure with single wide (25 nm) quantum well under
applied electric bias. Two-photon correlations were measured with the use of a
classical Hanbury Brown - Twiss intensity interferometer (time resolution ~0.4
ns). Photon "bunching" has been observed near the Bose condensation threshold
of dipolar excitons determined by the appearance of a narrow luminescence line
of exciton condensate at optical pumping increase. The two-photon correlation
function shows super-poissonian distribution at time scales of system coherence
(<~1 ns). No photon bunching was observed at the excitation pumping appreciably
below the condensation threshold. At excitation pumping increasing well above
the threshold, when the narrow line of exciton condensate grows in the
luminescence spectrum, the photon bunching is decreasing and finally vanishes -
the two-photon correlator becomes poissonian reflecting the
single-quantum-state origin of excitonic Bose condensate. Under the same
conditions a first-order spatial correlator, measured by means of the
luminescence interference from spatially separated condensate parts, remains
significant. The discovered photon bunching is rather sensitive to temperature:
it drops several times with temperature increase from 0.45 K up to 4.2 K. If
assumed that the luminescence of dipolar excitons collected in the lateral trap
reflects directly coherent properties of interacting exciton gas, the observed
phenomenon of photon bunching nearby condensation threshold manifests phase
transition in interacting exciton Bose gas.
\\ ( http://arxiv.org/abs/0907.3612 , 119kb)
Date: Tue, 21 Jul 2009 13:51:58 GMT (25kb)

Title: High-momentum tail in the Tonks-Girardeau gas under general confining
Authors: Gustavo A. Moreno
Categories: cond-mat.quant-gas
   We prove that the ground state momentum distribution of a one-dimensional
system of impenetrable bosons exhibits a $k^{-4}$ tail for any confining
potential. We also derive an expression for easily computing the asymptotic
occupation numbers and verify our results with an exact numerical approach.
\\ ( http://arxiv.org/abs/0907.3659 , 25kb)
Date: Tue, 21 Jul 2009 14:04:44 GMT (163kb,D)

Title: Lattice modulation spectroscopy of strongly interacting bosons in
   disordered and quasi-periodic optical lattices
Authors: G. Orso, A. Iucci, M. A. Cazalilla and T. Giamarchi
Categories: cond-mat.quant-gas
Comments: 11 pages, 8 figures
   We compute the absorption spectrum of strongly repulsive one-dimensional
bosons in a disordered or quasi-periodic optical lattice. At commensurate
filling, the particle-hole resonances of the Mott insulator are broadened as
the disorder strength is increased. In the non-commensurate case, mapping the
problem to the Anderson model allows us to study the Bose-glass phase.
Surprisingly we find that a perturbative treatment in both cases, weak and
strong disorder, gives a good description at all frequencies. In particular we
find that the infrared absorption rate in the thermodynamic limit is quadratic
in frequency. This result is unexpected, since for other quantities like the
conductivity in one dimensional systems, perturbation theory is only applicable
at high frequencies. We discuss applications to recent experiments on optical
lattice systems, and in particular the effect of the harmonic trap.
\\ ( http://arxiv.org/abs/0907.3663 , 163kb)
Date: Tue, 21 Jul 2009 19:22:09 GMT (103kb)

Title: A repulsive atomic gas in a harmonic trap on the border of itinerant
Authors: G.J. Conduit, B.D. Simons
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 5 pages, 4 figures
   Alongside superfluidity, itinerant ferromagnetism remains one of the most
well-characterised strongly correlated phases of fermionic matter. The
transition between ferromagnetism and paramagnetism with increasing temperature
is considered a canonical example of a continuous phase transition, and the
phenomenon has been firmly established in many materials. The ability to tune
the critical temperature through varying pressure presents experimentalists
with an opportunity to investigate novel many-body physics predicted to arise
in the vicinity of a quantum critical point. However, in the majority of
experimental systems, the transition is seen to turn first order at low
temperatures. Whether this phase behaviour derives from soft magnetic
fluctuations, which are believed to drive the Stoner transition first order, or
is a consequence of coupling to auxiliary degrees of freedom such as lattice
vibrations remains a subject of considerable interest and debate. The control
afforded by Feshbach resonance phenomena in ultracold degenerate Fermi gases,
which has been so successful in exploring resonance superfluidity in the regime
of BEC-BCS crossover, presents an opportunity to explore the correlated phase
behaviour predicted by Stoner theory. The aim of this letter is to identify key
experimental signatures of itinerant ferromagnetism in the atomic trap
geometry, and show that these results compare favourably with the findings of a
recent experimental study by Jo et al.
\\ ( http://arxiv.org/abs/0907.3725 , 103kb)
Date: Mon, 20 Jul 2009 14:26:55 GMT (953kb)

Title: Observation of the Anderson Metal-Insulator Transition with Atomic
   Matter Waves: Theory and Experiment
Authors: Gabriel Lemari\'e (LKB - Jussieu), Julien Chab\'e (PhLAM, CERLA),
   Pascal Szriftgiser (PhLAM, CERLA), Jean-Claude Garreau (PhLAM, CERLA),
   Beno\^it Gr\'emaud (LKB - Jussieu), Dominique Delande (LKB - Jussieu)
Categories: quant-ph cond-mat.dis-nn nlin.CD physics.optics
Comments: 19 pages, 15 figures, submitted to PRA
   Using a cold atomic gas exposed to laser pulses -- a realization of the
chaotic quasiperiodic kicked rotor with three incommensurate frequencies -- we
study experimentally and theoretically the Anderson metal-insulator transition
in three dimensions. Sensitive measurements of the atomic wavefunction and the
use of finite-size scaling techniques make it possible to unambiguously
demonstrate the existence of a quantum phase transition and to measure its
critical exponents. By taking proper account of systematic corrections to
one-parameter scaling, we show the universality of the critical exponent
$\nu=1.59\pm0.01,$ which is found to be equal to the one previously computed
for the Anderson model.
\\ ( http://arxiv.org/abs/0907.3411 , 953kb)
Date: Tue, 21 Jul 2009 20:00:07 GMT (41kb,D)

Title: Does thermalization occur in an isolated system after a global quantum
Authors: G. Biroli, C. Kollath, A. Laeuchli
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 4 pages, 1 figure
   We consider the question of thermalization for isolated quantum systems after
a sudden parameter change, a so-called quantum quench. In particular we
investigate the pre-requisites for thermalization focusing on the statistical
properties of the time-averaged density matrix and of the expectation values of
observables in the final eigenstates. We find that eigenstates, which are rare
compared to the typical ones sampled by the micro-canonical distribution, are
responsible for the absence of thermalization of some infinite integrable
models and play an important role for some finite size non-integrable systems,
such as the Bose-Hubbard model. We stress the importance of finite size effects
for the thermalization of isolated quantum systems and propose a condition,
relying on the Kullback-Leibler entropy, to obtain thermalization.
\\ ( http://arxiv.org/abs/0907.3731 , 41kb)
Date: Wed, 22 Jul 2009 10:56:06 GMT (346kb)

Title: Superfluid Quenching of the Moment of Inertia in a Strongly Interacting
   Fermi Gas
Authors: S. Riedl, E. R. Sanchez Guajardo, C. Kohstall, J. Hecker Denschlag, R.
Categories: cond-mat.quant-gas
   We report on the observation of a quenched moment of inertia as resulting
from superfluidity in a strongly interacting Fermi gas. Our method is based on
setting the hydrodynamic gas in slow rotation and determining its moment of
inertia by detecting the precession of a radial quadrupole excitation. The
measurements distinguish between the superfluid or collisional origin of
hydrodynamic behavior, and show the phase transition.
\\ ( http://arxiv.org/abs/0907.3814 , 346kb)
Date: Wed, 22 Jul 2009 18:16:47 GMT (164kb)

Title: Nonperturbative Thermodynamic Geometry of Anyon Gas
Authors: Behrouz Mirza, Hosein Mohammadzadeh
Categories: cond-mat.stat-mech cond-mat.quant-gas
Comments: 20 pages
   Following our earlier work on the Ruppeiner geometry of an anyon gas [B.
Mirza and H. Mohammadzadeh, Phys. Rev. E {\bf 78,} 021127 (2008)], we will
derive nonperturbative thermodynamic curvature of a two-dimensional ideal anyon
gas. At different values of the thermodynamic parameter space, some unique and
interesting behaviors of the anyon gas are explored. A complete picture of
attractive and repulsive phases of the anyon gas is given.
\\ ( http://arxiv.org/abs/0907.3899 , 164kb)
Date: Tue, 21 Jul 2009 20:59:02 GMT (123kb,D)

Title: Hyperfine-interaction- and magnetic-field-induced
   Bose-Einstein-statistics suppressed two-photon transitions
Authors: M. G. Kozlov, D. English, D. Budker
Categories: physics.atom-ph
   Two-photon transitions between atomic states of total electronic angular
momentum $J_a=0$ and $J_b=1$ are forbidden when the photons are of the same
energy. This selection rule is analogous to the Landau-Yang theorem in particle
physics that forbids decays of vector particle into two photons. It arises
because it is impossible to construct a total angular momentum $J_{2\gamma}=1$
quantum-mechanical state of two photons that is permutation symmetric, as
required by Bose-Einstein statistics. In atoms with non-zero nuclear spin, the
selection rule can be violated due to hyperfine interactions. Two distinct
mechanisms responsible for the hyperfine-induced two-photon transitions are
identified, and the hyperfine structure of the induced transitions is
evaluated. The selection rule is also relaxed, even for zero-nuclear-spin
atoms, by application of an external magnetic field. Once again, there are two
similar mechanisms at play: Zeeman splitting of the intermediate-state
sublevels, and off-diagonal mixing of states with different total electronic
angular momentum in the final state. The present theoretical treatment is
relevant to the ongoing experimental search for a possible
Bose-Einstein-statistics violation using two-photon transitions in barium,
where the hyperfine-induced transitions have been recently observed, and the
magnetic-field-induced transitions are being considered both as a possible
systematic effect, and as a way to calibrate the measurement.
\\ ( http://arxiv.org/abs/0907.3727 , 123kb)
Date: Wed, 22 Jul 2009 11:01:00 GMT (443kb)

Title: Quantum Control of Interacting Bosons in Periodic Optical Lattice
Authors: Analabha Roy Linda E. Reichl
Categories: physics.atom-ph
Comments: Sent to Physical Review A Corrected spelling mistake in name
   We study the avoided crossings in the dynamics of quantum controlled
excitations for an interacting two-boson system in an optical lattice.
Specifically, we perform numerical simulations of quantum control in this
system where driving pulses connect the undriven stationary states in a manner
characteristic of Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate
that the dynamics of such a transition is affected by chaos induced avoided
crossings, resulting in a loss in coherence of the final outcome in the
adiabatic limit.
\\ ( http://arxiv.org/abs/0907.3813 , 443kb)
Date: Thu, 23 Jul 2009 02:35:58 GMT (7kb)

Title: On supersolid fraction
Authors: Yongle Yu
Categories: cond-mat.supr-con
Comments: 1 page, 1 figure
   We present an explanation of why the observed supersolid fractions of helium
solids are rather far below unity. One might observe large supersolid fraction
of neon systems immersing in liquid $^3$He. A system of bosonic ions in a ring
trap could display a supersolid fraction close to unity.
\\ ( http://arxiv.org/abs/0907.3971 , 7kb)
Date: Thu, 23 Jul 2009 06:22:14 GMT (2164kb)

Title: Observation of shock waves in a large Bose-Einstein condensate
Authors: R. Meppelink, S. B. Koller, J. M. Vogels, P. van der Straten, E. D.
   van Ooijen, N. R. Heckenberg, H. Rubinsztein-Dunlop, S. A. Haine, and M. J.
Categories: cond-mat.quant-gas
Comments: 7 pages, 7 figures
   We observe the formation of shock waves in a Bose-Einstein condensate
containing a large number of sodium atoms. The shock wave is initiated with a
repulsive, blue-detuned light barrier, intersecting the BEC, after which two
shock fronts appear. We observe breaking of these waves when the size of these
waves approaches the healing length of the condensate. At this time, the wave
front splits into two parts and clear fringes appear. The experiment is modeled
using an effective 1D Gross-Pitaevskii-like equation and gives excellent
quantitative agreement with the experiment, even though matter waves with
wavelengths two orders of magnitude smaller than the healing length are
present. In these experiments, no significant heating or particle loss is
\\ ( http://arxiv.org/abs/0907.3989 , 2164kb)

The replacements:

replaced with revised version Fri, 17 Jul 2009 14:48:40 GMT (96kb)

Title: Stability of a BEC with Higher-order Interactions near a Feshbach
Authors: N.T. Zinner and M. Th{\o}gersen
Categories: cond-mat.other quant-ph
Comments: 4 pages, 3 figures, Revtex4, revised version, changed title
\\ ( http://arxiv.org/abs/0903.2261 , 96kb)
arXiv:0904.3107 (*cross-listing*)
replaced with revised version Fri, 17 Jul 2009 01:25:01 GMT (462kb)

Title: Nearly Perfect Fluidity: From Cold Atomic Gases to Hot Quark Gluon
Authors: Thomas Schaefer (North Carolina State University), Derek Teaney (SUNY
   Stony Brook and Riken-BNL)
Categories: hep-ph cond-mat.quant-gas hep-lat hep-th nucl-th
Comments: 76 pages, 11 figures, review article, extensive revisions
\\ ( http://arxiv.org/abs/0904.3107 , 462kb)
replaced with revised version Fri, 17 Jul 2009 02:41:32 GMT (222kb,D)

Title: Numerical method for evolving the dipolar projected Gross-Pitaevskii
Authors: P. B. Blakie, C. Ticknor, A. S. Bradley, A. M. Martin, M. J. Davis,
   and Y. Kawaguchi
Categories: cond-mat.quant-gas cond-mat.stat-mech physics.comp-ph
Comments: 16 pages, 6 figures. Updated to published version
Journal-ref: Phys. Rev. E 80, 016703 (2009)
DOI: 10.1103/PhysRevE.80.016703
\\ ( http://arxiv.org/abs/0904.3440 , 222kb)
replaced with revised version Fri, 17 Jul 2009 01:19:02 GMT (64kb)

Title: Cooling atoms into entangled states
Authors: Giovanni Vacanti and Almut Beige
Categories: quant-ph
Comments: 16 pages, 6 figures, typos corrected
\\ ( http://arxiv.org/abs/0903.2796 , 64kb)
replaced with revised version Sun, 19 Jul 2009 06:29:31 GMT (24kb,D)

Title: Kondo polarons in a one-dimensional Fermi gas
Authors: Austen Lamacraft
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: Published version
Journal-ref: Phys. Rev. Lett. 101, 225301 (2008)
\\ ( http://arxiv.org/abs/0805.0235 , 24kb)
replaced with revised version Mon, 20 Jul 2009 06:43:11 GMT (296kb)

Title: Statistical mechanics of a Feshbach coupled Bose-Fermi gas in an optical
Authors: O. Soe Sorensen, N. Nygaard, and P. B. Blakie
Categories: cond-mat.other
Comments: 9 pages, 5 figures
Journal-ref: Phys. Rev. A 79, 053601 (2009)
DOI: 10.1103/PhysRevA.79.053601
\\ ( http://arxiv.org/abs/0810.2696 , 296kb)
replaced with revised version Sun, 19 Jul 2009 08:11:33 GMT (120kb,D)

Title: Dispersion relation and spectral function of an impurity in a
   one-dimensional quantum liquid
Authors: Austen Lamacraft
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: Published version
Journal-ref: Phys. Rev. B 79, 241105(R) (2009)
\\ ( http://arxiv.org/abs/0810.4163 , 120kb)
replaced with revised version Mon, 20 Jul 2009 07:15:49 GMT (1187kb)

Title: Adiabatic cooling of a tunable Bose-Fermi mixture in an optical lattice
Authors: O. Soe Sorensen, N. Nygaard, P. B. Blakie
Categories: cond-mat.other
Comments: 10 pages, 7 figures
Journal-ref: Phys. Rev. A 79, 063615 (2009)
DOI: 10.1103/PhysRevA.79.063615
\\ ( http://arxiv.org/abs/0901.3625 , 1187kb)
replaced with revised version Mon, 20 Jul 2009 17:52:00 GMT (898kb)

Title: Ultracold three-body collisions near overlapping Feshbach resonances
Authors: J. P. D'Incao and B. D. Esry
Categories: physics.atom-ph
Comments: 4 pages, 3 figures, 1 table
\\ ( http://arxiv.org/abs/0905.0772 , 898kb)
replaced with revised version Mon, 20 Jul 2009 15:09:23 GMT (5623kb)

Title: Characterization and limits of a cold atom Sagnac interferometer
Authors: A. Gauguet (SYRTE), Benjamin Canuel (SYRTE), Thomas L\'ev\`eque
   (SYRTE), Walid Chaibi (ARTEMIS), Arnaud Landragin (SYRTE)
Categories: physics.atom-ph
\\ ( http://arxiv.org/abs/0907.2580 , 5623kb)
replaced with revised version Mon, 20 Jul 2009 15:43:21 GMT (1601kb,D)

Title: Decoherence via induced dipole collisions in an ultracold gas
Authors: Anthony R. Gorges, Mathew S. Hamilton, and Jacob L. Roberts
Categories: physics.atom-ph
Comments: 4 page, 4 figures
\\ ( http://arxiv.org/abs/0907.2884 , 1601kb)
replaced with revised version Wed, 22 Jul 2009 16:29:24 GMT (43kb)

Title: Andreev reflection in bosonic condensates
Authors: I. Zapata and F. Sols
Categories: cond-mat.other cond-mat.mes-hall cond-mat.supr-con
Comments: 5 pages, 3 figures. Text revised
Journal-ref: Phys. Rev. Lett. 102, 180405 (2009)
DOI: 10.1103/PhysRevLett.102.180405
\\ ( http://arxiv.org/abs/0804.4631 , 43kb)
replaced with revised version Wed, 22 Jul 2009 08:57:30 GMT (61kb)

Title: Superfluid to Bose-glass transition in a 1D weakly interacting Bose gas
Authors: Luca Fontanesi, Michiel Wouters, Vincenzo Savona
Categories: cond-mat.quant-gas cond-mat.dis-nn
Comments: 4 pages, 4 figures
Journal-ref: Phys. Rev. Lett. 103, 030403 (2009)
DOI: 10.1103/PhysRevLett.103.030403
\\ ( http://arxiv.org/abs/0904.3643 , 61kb)
replaced with revised version Wed, 22 Jul 2009 06:02:06 GMT (2384kb)

Title: Towards a random laser with cold atoms
Authors: William Guerin (INLN), Nicolas Mercadier (INLN), Franck Michaud
   (INLN), Davide Brivio (INLN), Luis S. Froufe-P\'erez, R\'emi Carminati (LOA),
   Vitalie Eremeev (LPMMC), Arthur Goetschy (LPMMC), Sergey E. Skipetrov
   (LPMMC), Robin Kaiser (INLN)
Categories: physics.atom-ph cond-mat.dis-nn physics.optics
Comments: Accepcted for publication by J. Opt. A for the special issue on
   nanolasers and random lasers (to be published early 2010)
\\ ( http://arxiv.org/abs/0906.0714 , 2384kb)
replaced with revised version Thu, 23 Jul 2009 13:15:54 GMT (1240kb)

Title: Atomic Quantum Corrals for Bose-Einstein Condensates
Authors: Hongwei Xiong and Biao Wu
Categories: cond-mat.other
Comments: 6 pages, 7 figures
\\ ( http://arxiv.org/abs/0812.4602 , 1240kb)
replaced with revised version Thu, 23 Jul 2009 13:44:35 GMT (851kb)

Title: Shell-Model Monte Carlo Simulations of BCS-BEC Crossover in Few-Fermion
Authors: N.T. Zinner, K. M{\o}lmer, C. \"Ozen, D.J. Dean, K. Langanke
Categories: cond-mat.supr-con cond-mat.quant-gas nucl-th
Comments: 6 pages, 5 figures, Revtex4, final version
\\ ( http://arxiv.org/abs/0903.2263 , 851kb)

Till next time,

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
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