Matt's arXiv selection: week ending 10 April 2009

From: Matthew Davis <>
Date: Mon, 25 May 2009 08:41:26 +1000

The following message was sent to the matts_arxiv list by Matthew Davis <>

Dear subscribers,

We have Jacopo Sabbatini to thank for this week's message. There are 18 new
preprints and 6 replacements.

Date: Fri, 3 Apr 2009 14:28:39 GMT (3kb)

Title: Doublon-Holon binding in a half-filled band
Authors: Philip Phillips
Categories: cond-mat.str-el
Comments: This is a 1-page comment on S. Sakai, Y. Motome, and M. Imada, PRL,
   vol. 102, 056404 (2009)
   The arguments presented in PRL. vol. 102, 056404 (2009) are discussed in the
context of the vast literature on spectral weight transfer in doped Mott
insulators. We show that the conclusions regarding spectral weight transfer in
PRL. vol. 102, 056404 (2009) are, where novel, internally inconsistent and
where correct, have been reached at least 18 years ago.
\\ ( , 3kb)
Date: Thu, 2 Apr 2009 22:17:06 GMT (87kb)

Title: Application of the Feshbach-resonance management to a tightly confined
   Bose-Einstein condensate
Authors: Giovanni Filatrella, Boris A. Malomed and Luca Salasnich
Categories: cond-mat.quant-gas cond-mat.other
Comments: Physical Review A, in press
   We study suppression of the collapse and stabilization of matter-wave
solitons by means of time-periodic modulation of the effective nonlinearity,
using the nonpolynomial Schroedinger equation (NPSE) for BEC trapped in a tight
cigar-shaped potential. By means of systematic simulations, a stability region
is identified in the plane of the modulation amplitude and frequency. In the
low-frequency regime, solitons feature chaotic evolution, although they remain
robust objects.
\\ ( , 87kb)
Date: Fri, 3 Apr 2009 13:43:42 GMT (33kb)

Title: Multi-particle composites in density-imbalanced quantum fluids
Authors: Evgeni Burovski, Giuliano Orso, and Thierry Jolicoeur
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 4+ pages, 1 figure
   We consider two-component one-dimensional quantum gases with density
imbalance. While generically such fluids are two-component Luttinger liquids,
we show that if the ratio of the densities is a rational number, p/q, and mass
asymmetry between components is sufficiently strong, one of the two eigenmodes
acquires a gap. The gapped phase corresponds to (algebraic) ordering of
(p+q)-particle composites. In particular, for attractive mixtures, this implies
that the superconducting correlations are destroyed. We illustrate our
predictions by numerical simulations of the fermionic Hubbard model with
hopping asymmetry.
\\ ( , 33kb)
Date: Thu, 2 Apr 2009 05:53:08 GMT (168kb)

Title: All-optical Imprinting of Geometric Phases onto Matter Waves
Authors: Qi Zhang, Jiangbin Gong, and C.H. Oh
Categories: quant-ph cond-mat.quant-gas
Comments: 5 pages, 2 figures, to appear in Phys. Rev. A
   Traditional optical phase imprinting of matter waves is of a dynamical
nature. In this paper we show that both Abelian and non-Abelian geometric
phases can be optically imprinted onto matter waves, yielding a number of
interesting phenomena such as wavepacket re-directing and wavepacket splitting.
In addition to their fundamental interest, our results open up new
opportunities for robust optical control of matter waves.
\\ ( , 168kb)
Date: Mon, 6 Apr 2009 12:46:56 GMT (23kb)

Title: Bose systems in spatially random or time-varying potentials
Authors: V.I. Yukalov, E.P. Yukalova, and V.S. Bagnato
Categories: cond-mat.dis-nn cond-mat.mes-hall
Comments: latex file, 26 pages, 1 figure
Journal-ref: Laser Phys. 19 (2009) 686-699
   Bose systems, subject to the action of external random potentials, are
considered. For describing the system properties, under the action of spatially
random potentials of arbitrary strength, the stochastic mean-field
approximation is employed. When the strength of disorder increases, the
extended Bose-Einstein condensate fragments into spatially disconnected
regions, forming a granular condensate. Increasing the strength of disorder
even more transforms the granular condensate into the normal glass. The
influence of time-dependent external potentials is also discussed. Fast varying
temporal potentials, to some extent, imitate the action of spatially random
potentials. In particular, strong time-alternating potential can induce the
appearance of a nonequilibrium granular condensate.
\\ ( , 23kb)
Date: Mon, 6 Apr 2009 12:25:55 GMT (77kb)

Title: Process chain approach to the Bose-Hubbard model: Ground-state
   properties and phase diagram
Authors: Niklas Teichmann, Dennis Hinrichs, Martin Holthaus, Andre Eckardt
Categories: cond-mat.other
Comments: 15 pages, 20 figures
   We carry out a perturbative analysis, of high order in the tunneling
parameter, of the ground state of the homogeneous Bose-Hubbard model in the
Mott insulator phase. This is made possible by a diagrammatic process chain
approach, derived from Kato's representation of the many-body perturbation
series, which can be implemented numerically in a straightforward manner. We
compute ground-state energies, atom-atom correlation functions, density-density
correlations, and occupation number fluctuations, for one-, two-, and
three-dimensional lattices with arbitrary integer filling. A phenomenological
scaling behavior is found which renders the data almost independent of the
filling factor. In addition, the process chain approach is employed for
calculating the boundary between the Mott insulator phase and the superfluid
phase with high accuracy. We also consider systems with dimensionalities d>3,
thus monitoring the approach to the mean-field limit. The versatility of the
method suggests further applications to other systems which are less well
\\ ( , 77kb)
Date: Mon, 6 Apr 2009 14:45:41 GMT (951kb)

Title: Collisions of Ultracold Trapped Cesium Feshbach Molecules
Authors: F. Ferlaino, S. Knoop, M. Berninger, M. Mark, H.-C. Naegerl, and R.
Categories: cond-mat.quant-gas cond-mat.other
Comments: To appear in Laser Physics, special issue in memoriam Prof. Vladilen
   S. Letokhov
   We study collisions in an optically trapped, pure sample of ultracold Cs$_2$
molecules in various internal states. The molecular gas is created by Feshbach
association from a near-degenerate atomic gas, with adjustable temperatures in
the nanokelvin range. We identify several narrow loss resonances, which point
to the coupling to more complex molecular states and may be interpreted as
Feshbach resonances in dimer-dimer interactions. Moreover, in some molecular
states we observe a surprising temperature dependence in collisional loss. This
shows that the situation cannot be understood in terms of the usual simple
threshold behavior for inelastic two-body collisions. We interpret this
observation as further evidence for a more complex molecular structure beyond
the well-understood dimer physics.
\\ ( , 951kb)
Date: Mon, 6 Apr 2009 18:13:20 GMT (89kb)

Title: Dynamical phase transition in correlated fermionic lattice systems
Authors: Martin Eckstein, Marcus Kollar, Philipp Werner
Categories: cond-mat.str-el
Comments: 4 pages, 3 figures
   We use non-equilibrium dynamical mean-field theory to demonstrate the
existence of a critical interaction in the real-time dynamics of the Hubbard
model after an interaction quench. The critical point is characterized by fast
thermalization and separates weak-coupling and strong-coupling regimes in which
the relaxation is delayed due to prethermalization on intermediate timescales.
This dynamical phase transition should be observable in experiments on trapped
fermionic atoms.
\\ ( , 89kb)
Date: Thu, 9 Oct 2008 18:59:30 GMT (68kb)

Title: Momentum-space interferometry with trapped ultracold atoms
Authors: A. Ruschhaupt, A. del Campo, J. G. Muga
Categories: quant-ph cond-mat.quant-gas
Comments: 8 pages
Journal-ref: Phys. Rev. A 79, 023616 (2009)
   Quantum interferometers are generally set so that phase differences between
paths in coordinate space combine constructive or destructively. Indeed, the
interfering paths can also meet in momentum space leading to momentum-space
fringes. We propose and analyze a method to produce interference in momentum
space by phase-imprinting part of a trapped atomic cloud with a detuned laser.
For one-particle wave functions analytical expressions are found for the fringe
width and shift versus the phase imprinted. The effects of unsharpness or
displacement of the phase jump are also studied, as well as many-body effects
to determine the potential applicability of momentum-space interferometry.
\\ ( , 68kb)
Date: Mon, 6 Apr 2009 23:50:51 GMT (817kb)

Title: Drag force on an impurity below the superfluid critical velocity in a
   quasi-one-dimensional Bose-Einstein condensate
Authors: Andrew G. Sykes, Matthew J. Davis, and David C. Roberts
Categories: cond-mat.quant-gas
Comments: 7 pages (including supplementary material)
   The existence of frictionless flow below a critical velocity for obstacles
moving in a superfluid is well established in the context of the mean-field
Gross-Pitaevskii theory. We calculate the next order correction due to quantum
and thermal fluctuations and find a non-zero force acting on a delta-function
impurity moving through a quasi-one-dimensional Bose-Einstein condensate at all
subcritical velocities and at all temperatures. The force occurs due to an
imbalance in the Doppler shifts of reflected quantum fluctuations from either
side of the impurity. Our calculation is based on a consistent extension of
Bogoliubov theory to second order in the interaction strength, and finds new
analytical solutions to the Bogoliubov-de Gennes equations for a gray soliton.
Our results raise questions regarding the quantum dynamics in the formation of
persistent currents in superfluids.
\\ ( , 817kb)
Date: Tue, 7 Apr 2009 14:53:59 GMT (514kb)

Title: Spin dynamics and structure formation in a spin-1 condensate in a
   magnetic field
Authors: Jordi Mur-Petit (UCL)
Categories: cond-mat.quant-gas
Comments: 8 pages, 5 figures
   We study the dynamics of a trapped spin-1 condensate in a magnetic field.
First, we analyze the homogeneous system, for which the dynamics can be
understood in terms of orbits in phase space, and we solve analytically for the
dynamical evolution of the populations of the various Zeeman components of the
homogeneous system. This result is then applied via a Local Density
Approximation to trapped quasi-1D condensates. Our analysis of the trapped
system in a magnetic field shows that both mean-field and Zeeman regimes are
simultaneously present, and argue that the border between these two regions is
where spin domains and phase defects are generated. We finally propose a method
to experimentally tune the position of this border.
\\ ( , 514kb)
Date: Tue, 7 Apr 2009 20:22:24 GMT (1561kb)

Title: Theory of domain formation in inhomogeneous ferromagnetic dipolar
Authors: Jay D. Sau, S. R. Leslie, D. M. Stamper-Kurn, Marvin L. Cohen
Categories: cond-mat.quant-gas
Comments: 26 pages, 8 figures
   Recent experimental studies of $^{87}$Rb spinor Bose Einstein condensates
have shown the existence of a magnetic field driven quantum phase transition
accompanied by structure formation on the ferromagnetic side of the transition.
In this theoretical study we examine the dynamics of the unstable modes
following the transition taking into account the effects of the trap,
non-linearities, finite temperature and dipole-dipole interactions. Starting
from an initial state which includes quantum fluctuations, we attempt to make
quantitative comparisons with recent experimental data on this system and
estimate the contribution of quantum zero-point fluctuations to the domain
formation. Finally, using the strong anisotropy of the trap, we propose ways to
observe directly the effects of dipole-dipole interactions on the spinor
condensate dynamics.
\\ ( , 1561kb)
Date: Wed, 8 Apr 2009 14:11:01 GMT (2129kb)

Title: Spectral Functions and rf Response of Ultracold Fermionic Atoms
Authors: R. Haussmann, M. Punk, and W. Zwerger
Categories: cond-mat.quant-gas
Comments: 15 pages, 5 figures, revtex 4
   We present a calculation of the spectral functions and the associated rf
response of ultracold fermionic atoms near a Feshbach resonance. The single
particle spectra are peaked at energies that can be modelled by a modified BCS
dispersion. Even at very low temperatures, however, their width is comparable
to their energy and thus the standard BCS description of fermionic superfluids
by well-defined Bogoliubov quasiparticles does not apply. The structure of the
broad excitation spectrum of the unitary gas at infinite scattering length
agrees with recent momentum-resolved rf spectra near the critical temperature.
A detailed comparison is made with momentum integrated, locally resolved rf
spectra of the unitary gas at arbitrary temperatures and shows very good
agreement between theory and experiment. The pair size defined from the width
of these spectra is found to coincide with that obtained from the leading
gradient corrections to the effective field theory of the superfluid.
\\ ( , 2129kb)
Date: Wed, 8 Apr 2009 14:10:21 GMT (41kb)

Title: Quantum Phase Transitions in a Dimerized Bose-Hubbard Model: A DMRG
Authors: Anasuya Kundu and Swapan K Pat
Categories: cond-mat.quant-gas
Comments: 5 pages, 4 figures
Journal-ref: Europhysics Letters 85, 43001 (2009)
   We investigate the phase diagram of a dimerized Bose-Hubbard model, using
density matrix renormalization group technique. We find a new phase, which is
the coexistence of superfluid and bond-wave phases, due to the effect of
dimerization. Experimentally dimerization in optical lattice can be realized by
using two counter propagating laser beams of different wavelengths. Apart from
the conventional superfluid to Mott insulator transition, we find a new quantum
phase transition: from superfluid-bond-wave to Mott insulator-bond wave phase.
Our study suggests a rich phase diagram which can be easily probed.
\\ ( , 41kb)
arXiv:0901.3345 (*cross-listing*)
Date: Wed, 21 Jan 2009 20:50:35 GMT (470kb)

Title: Quantum dynamics of instability-induced pulsations of a Bose-Einstein
   condensate in an optical lattice
Authors: Uttam Shrestha, Juha Javanainen, and Janne Ruostekoski
Categories: cond-mat.other quant-ph
   We study the dynamics of a Bose-Einstein condensate in a one-dimensional
optical lattice in the limit of weak atom-atom interactions, including an
approximate model for quantum fluctuations. A pulsating dynamical instability
in which atoms periodically collect together and subsequently disperse back
into the initial homogeneous state may occur in the time evolution. We take
into account the quantum fluctuations within the truncated Wigner
approximation. We observe that the quasiperiodic behavior still persists for a
single realization that represents a typical experimental outcome, but ensemble
averages show various manifestations of quantum fluctuations. Quantum effects
become more prominent when the effective interaction strength is increased.
\\ ( , 470kb)
Date: Thu, 9 Apr 2009 13:50:26 GMT (875kb)

Title: In-situ Observation of Incompressible Mott-Insulating Domains of
   Ultracold Atomic Gases
Authors: Nathan Gemelke, Xibo Zhang, Chen-Lung Hung, Cheng Chin
Categories: cond-mat.quant-gas
   We present a direct measurement of the density profile of a two-dimensional
Mott Insulator formed by ultracold atoms in an optical lattice. High resolution
absorption imaging is used to probe the "wedding-cake" structure of a trapped
gas as it crosses the boundary from a unit-filled Mott insulating phase to the
superfluid phase at finite temperature. Detailed analysis of images yields
measurements of temperature and local compressibility; for the latter we
observe a strong suppression deep in the Mott-insulating phase, which is
recovered for the superfluid and normal phases. Furthermore, we measure
spatially resolved fluctuations in the local density, showing a suppression of
fluctuations in the insulator. Results are consistent with the
fluctuation-dissipation theorem for insulator, superfluid and normal gas.
\\ ( , 875kb)
Date: Thu, 9 Apr 2009 15:46:57 GMT (366kb)

Title: Pair-supersolid phase in a bilayer system of dipolar lattice bosons
Authors: C. Trefzger, C. Menotti, and M. Lewenstein
Categories: cond-mat.other
Comments: 4 pages, 4 figures
   The competition between tunneling and interactions in bosonic lattice models
generates a whole variety of different quantum phases. While, in the presence
of a single species interacting via on-site interaction, the phase diagram
presents only superfluid or Mott insulating phases, for long-range interactions
or multiple species, exotic phases such as supersolid (SS) or pair-superfluid
(PSF) appear. In this work, we show for the first time that the co-existence of
effective multiple species and long-range interactions leads to the formation
of a novel pair-supersolid (PSS) phase, namely a supersolid of composites. We
propose a possible implementation with dipolar bosons in a bilayer
two-dimensional optical lattice.
\\ ( , 366kb)
Date: Thu, 9 Apr 2009 17:01:21 GMT (6964kb)

Title: Induced interaction and crystallization of self-localized impurity
   fields in a Bose-Einstein condensate
Authors: Sergio Rica and David C. Roberts
Categories: cond-mat.quant-gas
Comments: 16 pages, 9 figures, (33 fig. files including subfigures)
   We model the behavior of N classical impurity fields immersed in a larger
Bose-Einstein condensate by N+1 coupled nonlinear Schr\"odinger equations in 1,
2, and 3 space dimensions. We discuss the stability of the uniform miscible
system and show the importance of surface tension for self localization of the
impurity fields. We derive analytically the attractive tail of
impurity-impurity interaction due to mediation by the underlying condensate.
Assuming all impurity fields interact with the same strength, we explore
numerically the resulting phase diagram, which contains four phases: I) all
fields are miscible; II) the impurity fields are miscible with each other but
phase separate from the condensate as a single bubble; III) the localized
impurity fields stay miscible with the condensate, but not with each other; and
IV) the impurity fields phase separate from the condensate and each other,
forming a crystalline structure within a bubble. Finally, we argue that the
crystalline phases maintain their superfluid behavior, i.e. they possess a
nonclassical rotational inertia, which, combined with lattice order, is a
characteristic of supersolidity.
\\ ( , 6964kb)

The replacements:

replaced with revised version Fri, 3 Apr 2009 16:35:18 GMT (203kb)

Title: Independent Control of Scattering Lengths in Multicomponent Quantum
Authors: Peng Zhang, Pascal Naidon and Masahito Ueda
Categories: physics.atom-ph cond-mat.other quant-ph
Comments: 4pages, 3figures
\\ ( , 203kb)
replaced with revised version Fri, 3 Apr 2009 02:05:24 GMT (315kb)

Title: Repulsive Fermi gas in a harmonic trap: Ferromagnetism and spin textures
Authors: L. J. LeBlanc, J. H. Thywissen, A. A. Burkov, A. Paramekanti
Categories: cond-mat.quant-gas
Comments: 9 pages, 4 figures (minor typos in text+fig corrected)
\\ ( , 315kb)
replaced with revised version Sat, 4 Apr 2009 18:03:02 GMT (607kb)

Title: Nonequilibrium Josephson oscillations in Bose-Einstein condensates
   without dissipation
Authors: Mauricio Trujillo Martinez, Anna Posazhennikova, and Johann Kroha
Categories: cond-mat.quant-gas cond-mat.other
Comments: 4 pages, 4 figures
\\ ( , 607kb)
replaced with revised version Tue, 7 Apr 2009 08:43:33 GMT (1045kb)

Title: Generalized Dynamical Mean-Field Theory for Bose-Fermi Mixtures in
   Optical Lattices
Authors: I. Titvinidze, M. Snoek, and W. Hofstetter
Categories: cond-mat.other
Comments: 12+ pages 6 figures
Journal-ref: Phys. Rev. B 79, 144506 (2008)
DOI: 10.1103/PhysRevB.79.144506
\\ ( , 1045kb)
replaced with revised version Thu, 9 Apr 2009 11:55:54 GMT (431kb)

Title: Determination of atomic scattering lengths from measurements of
   molecular binding energies near Feshbach resonances
Authors: A. D. Lange, K. Pilch, A. Prantner, F. Ferlaino, B. Engeser, H.-C.
   Naegerl, R. Grimm, and C. Chin
Categories: cond-mat.other cond-mat.quant-gas physics.atom-ph
Comments: 6 pages, 4 figures
Journal-ref: Phys. Rev. A 79, 013622 (2009)
\\ ( , 431kb)
replaced with revised version Thu, 9 Apr 2009 11:38:58 GMT (1126kb)

Title: Evidence for Universal Four-Body States Tied to an Efimov Trimer
Authors: F. Ferlaino, S. Knoop, M. Berninger, W. Harm, J. P. D'Incao, H.-C.
   N\"agerl, and R. Grimm
Categories: cond-mat.other cond-mat.quant-gas physics.atom-ph quant-ph
Comments: 4 pages, 4 figures
Journal-ref: Phys. Rev. Lett. 102, 140401 (2009)
\\ ( , 1126kb)

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,        
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Fri May 29 2009 - 08:38:24 EST

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