Dear subscribers,
This week's selection was compiled by Chris Foster, and contains 24 new
abstracts and 6 replacements.
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arXiv:1007.4038
Date: Fri, 23 Jul 2010 03:08:56 GMT (4224kb)
Title: Robust Mesoscopic Superposition of Ultracold Atoms
Authors: David W. Hallwood, Thomas Ernst, Joachim Brand
Categories: quant-ph
Comments: 7 pages, 4 figures
\\
Quantum superpositions of macroscopically distinct states, as in
Schroedinger's example of a dead and alive cat, are important for our
understanding of quantum mechanics and carry great promise for enhanced
precision measurement techniques. Due to their inherent fragility, the
maximally entangled "NOON" states engineered in optics and spin systems for
ultra-precise spectroscopy have been limited to 10 particles. The related
mesoscopic superpositions of flux states consisting of 10^9 Cooper pairs
observed in superconducting rings have proven more robust but their microscopic
nature is debated. Binary superpositions with multiple ultra-cold atoms have
not yet been seen and existing proposals suffer severe limitations due to
decoherence and the unfavorable scaling of precision and time scales needed to
produce these states. In this paper we show how robust superpositions of
mesoscopic flow in a ring trap can be made with strongly-correlated ultra-cold
atoms under one-dimensional confinement. We present a microscopic model that
explains how flow states become robust to single-particle loss due to strong
correlations between atoms. The attainable spectroscopic energy separation
scales linearly with particle number and thus does not limit the system size.
Our results introduce a new type of binary superposition state that involves
mesoscopically distinct and strongly correlated quantum states.
\\ ( http://arxiv.org/abs/1007.4038 , 4224kb)
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arXiv:1007.4088
Date: Fri, 23 Jul 2010 09:58:32 GMT (555kb)
Title: Bose-Einstein condensation of photons in an optical microcavity
Authors: Jan Klaers, Julian Schmitt, Frank Vewinger, and Martin Weitz
Categories: cond-mat.quant-gas
\\
Bose-Einstein condensation, the macroscopic ground state accumulation of
particles with integer spin (bosons) at low temperature and high density, has
been observed in several physical systems, including cold atomic gases and
solid state physics quasiparticles. However, the most omnipresent Bose gas,
blackbody radiation (radiation in thermal equilibrium with the cavity walls)
does not show this phase transition, because the chemical potential of photons
vanishes and, when the temperature is reduced, photons disappear in the cavity
walls. Theoretical works have considered photon number conserving
thermalization processes, a prerequisite for Bose-Einstein condensation, using
Compton scattering with a gas of thermal electrons, or using photon-photon
scattering in a nonlinear resonator configuration. In a recent experiment, we
have observed number conserving thermalization of a two-dimensional photon gas
in a dye-filled optical microcavity, acting as a 'white-wall' box for photons.
Here we report on the observation of a Bose-Einstein condensation of photons in
a dye-filled optical microcavity. The cavity mirrors provide both a confining
potential and a non-vanishing effective photon mass, making the system formally
equivalent to a two-dimensional gas of trapped, massive bosons. By multiple
scattering off the dye molecules, the photons thermalize to the temperature of
the dye solution (room temperature). Upon increasing the photon density we
observe the following signatures for a BEC of photons: Bose-Einstein
distributed photon energies with a massively populated ground state mode on top
of a broad thermal wing, the phase transition occurring both at the expected
value and exhibiting the predicted cavity geometry dependence, and the ground
state mode emerging even for a spatially displaced pump spot.
\\ ( http://arxiv.org/abs/1007.4088 , 555kb)
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arXiv:1007.4296
Date: Sun, 25 Jul 2010 02:46:41 GMT (880kb)
Title: Quantum thermalization of two coupled two-level systems in both
eigenstate and bare-state representations
Authors: Jie-Qiao Liao, Jin-Feng Huang, Le-Man Kuang
Categories: quant-ph
Comments: 12 pages, 5 figures
\\
We study analytically the quantum thermalization of two coupled two-level
systems (TLSs), which are connected with either two independent heat baths
(IHBs) or a common heat bath (CHB). We understand the quantum thermalization in
both eigenstate and bare-state representations when the coupling strength
between the two TLSs is strong and weak, respectively. In the IHB case, we find
that when the two IHBs have the same temperatures, the two coupled TLSs in the
eigenstate representation can be thermalized with the same temperature as those
of the IHBs. However, for the case that the two IHBs have different
temperatures, just when the energy detuning between the two TLSs satisfies a
special condition, the two coupled TLSs can be thermalized with an immediate
temperature between those of the two IHBs. For the weak coupling case, we find
a counterintuitive phenomenon that the temperature of the TLS connected with
the high-temperature heat bath is lower than that of the other TLS, which is
connected with the low-temperature heat bath under certain conditions. In the
CHB case, the coupled TLSs in the eigenstate representation can be thermalized
with the same temperature as that of the CHB for the nonresonant cases. We also
find that the TLS with a larger energy separation can be thermalized to a
thermal equilibrium with a lower temperature in the bare-state representation.
Especially, we find a phenomenon of anti-thermalization for the two TLSs
connected with a CHB in the resonant case.
\\ ( http://arxiv.org/abs/1007.4296 , 880kb)
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arXiv:1007.4339 (*cross-listing*)
Date: Sun, 25 Jul 2010 18:18:57 GMT (976kb)
Title: Optical excitation of nonlinear spin waves
Authors: J.M. McGuirk, L.F. Zajiczek
Categories: cond-mat.quant-gas physics.atom-ph
Comments: 11 pages, 5 figures
\\
We demonstrate a technique for exciting spin waves in an ultracold gas of
Rb-87 atoms based on tunable AC Stark potentials. This technique allows us to
excite normal modes of spin waves with arbitrary amplitudes in the trapped gas,
including dipole, quadrupole, octupole, and hexadecapole modes. These modes
exhibit strong nonlinearities, which manifest as amplitude dependence of the
excitation frequencies and departure from sinusoidal behavior. We find good
agreement with a full treatment of a quantum Boltzmann transport equation.
\\ ( http://arxiv.org/abs/1007.4339 , 976kb)
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arXiv:1007.4422
Date: Mon, 26 Jul 2010 11:17:22 GMT (415kb)
Title: Structure and stability of quasi-two-dimensional boson-fermion mixtures
with vortex-antivortex superposed states
Authors: Linghua Wen, Yongping Zhang, Jian Feng
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 8 pages,5 figures
\\
We investigate the equilibrium properties of a quasi-two-dimensional
degenerate boson-fermion mixture (DBFM) with a bosonic vortex-antivortex
superposed state (VAVSS) using a quantum-hydrodynamic model. We show that,
depending on the choice of parameters, the DBFM with a VAVSS can exhibit rich
phase structures. For repulsive boson-fermion (BF) interaction, the
Bose-Einstein condensate (BEC) may constitute a petal-shaped "core" inside the
honeycomb-like fermionic component, or a ring-shaped joint "shell" around the
onion-like fermionic cloud, or multiple cake-shaped configurations embedded in
the disc-shaped Fermi gas. For attractive BF interaction just below the
threshold for collapse, an almost complete mixing between the bosonic and
fermionic components is formed, where the fermionic component tends to mimic a
bosonic VAVSS. The influence of an anharmonic trap on the density distributions
of the DBFM with a bosonic VAVSS is discussed. In addition, a stability diagram
for three different cases of DBFM (without vortex, with a bosonic vortex, and
with a bosonic VAVSS) with specific parameters is given.
\\ ( http://arxiv.org/abs/1007.4422 , 415kb)
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arXiv:1007.4441 (*cross-listing*)
Date: Mon, 26 Jul 2010 12:47:56 GMT (5071kb,D)
Title: Dispersive bottleneck delaying thermalization of turbulent Bose-Einstein
Condensates
Authors: Giorgio Krstulovic and Marc Brachet
Categories: physics.flu-dyn cond-mat.quant-gas
\\
Using initial conditions with mass and energy distributed at large scales a
new mechanism of thermalization involving a direct energy cascade is obtained
in the truncated Gross-Pitaevskii dynamics. A long transient with partial
thermalization at small-scales is observed before the system reaches
equilibrium. Vortices are found to disappear as a prelude to final
thermalization. A bottleneck that produces spontaneous effective self
truncation and delays thermalization is characterized when large dispersive
effects are present at the truncation wavenumber. Based on order of magnitude
estimates, this effect should be present in weakly interacting Bose-Einstein
condensates.
\\ ( http://arxiv.org/abs/1007.4441 , 5071kb)
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arXiv:1007.4504
Date: Mon, 26 Jul 2010 16:53:24 GMT (16kb)
Title: Spin fluctuations, susceptibility and the dipole oscillation of a nearly
ferromagnetic Fermi gas
Authors: Alessio Recati and Sandro Stringari
Categories: cond-mat.quant-gas
Comments: 5 pages, 2 figures
\\
We discuss the spin fluctuations and the role played by the magnetic
susceptibility in an atomic Fermi gas interacting with positive scattering
length. Both thermal and quantum fluctuations are considered. Using a sum rule
approach and recent {\it ab initio} Monte Carlo results for the magnetic
susceptibility of uniform matter we provide explicit predictions for the
frequency of the spin dipole oscillation of a gas trapped by a harmonic
potential and discuss the deviations from the behaviour of an ideal gas when
the system approaches the ferromagnetic transition. The role of the Landau's
parameters in the characterization of the magnetic properties is also
discussed.
\\ ( http://arxiv.org/abs/1007.4504 , 16kb)
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arXiv:1007.4607
Date: Tue, 27 Jul 2010 02:05:12 GMT (226kb,D)
Title: Localization of solitons: linear response of the mean-field ground state
to weak external potentials
Authors: Cord A. Mueller
Categories: cond-mat.quant-gas
Comments: Submitted to Appl. Phys. B; selected paper presented at the 2010
Spring Meeting of the Quantum Optics and Photonics Section of the German
Physical Society
\\
Two aspects of bright matter-wave solitons in weak external potentials are
discussed. First, we briefly review recent results on the Anderson localization
of an entire soliton in disordered potentials [Sacha et al. PRL 103, 210402
(2009)], as a paradigmatic showcase of genuine quantum dynamics beyond simple
perturbation theory. Second, we calculate the linear response of the mean-field
soliton shape to a weak, but otherwise arbitrary external potential, with a
detailed application to lattice potentials.
\\ ( http://arxiv.org/abs/1007.4607 , 226kb)
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arXiv:1007.4640
Date: Tue, 27 Jul 2010 08:44:19 GMT (747kb,D)
Title: Bose condensation in flat bands
Authors: Sebastian D. Huber and Ehud Altman
Categories: cond-mat.str-el cond-mat.quant-gas
Comments: 18 pages, 13 figures
\\
We derive effective Hamiltonians for lattice bosons with strong geometrical
frustration of the kinetic energy by projecting the interactions on the flat
lowest Bloch band. Specifically, we consider the Bose Hubbard model on the one
dimensional sawtooth lattice and the two dimensional kagome lattice. Starting
from a strictly local interaction the projection gives rise to effective
long-range terms stabilizing a supersolid phase at densities above nu_c=1/9 of
the kagome lattice. In the sawtooth lattice on the other hand we show that the
solid order, which exists at the magic filling nu_c=1/4, is unstable to further
doping. The universal low-energy properties at filling 1/4+delta nu are
described by the well known commensurate-incommensurate transition. We support
the analytic results by detailed numerical calculations using the Density
Matrix Renormalization Group and exact diagonalization. Finally, we discuss
possible realizations of the models using ultracold atoms as well as frustrated
quantum magnets in high magnetic fields. We compute the momentum distribution
and the noise correlations, that can be extracted from time of flight
experiments or neutron scattering, and point to signatures of the unique
supersolid phase of the kagome lattice.
\\ ( http://arxiv.org/abs/1007.4640 , 747kb)
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arXiv:1007.4672
Date: Tue, 27 Jul 2010 10:53:24 GMT (198kb)
Title: Tunneling of polarized fermions in 3D double wells
Authors: Tommaso Macri and Andrea Trombettoni
Categories: cond-mat.quant-gas
Comments: 13 pages, 9 figures
\\
We study the tunneling of a spin polarized Fermi gas in a three-dimensional
double well potential, focusing on the time dynamics starting from an initial
state in which there is an imbalance in the number of particles in the two
wells. Although fermions in different doublets of the double well tunnel with
different frequencies, we point out that (incoherent) oscillations of a large
number of particles can arise, as a consequence of the presence of transverse
degrees of freedom. Estimates of the doublet structure and of the occupation of
transverse eigenstates for a realistic experimental setup are provided.
\\ ( http://arxiv.org/abs/1007.4672 , 198kb)
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arXiv:1007.4686
Date: Tue, 27 Jul 2010 11:59:25 GMT (1217kb)
Title: Room temperature one-dimensional polariton condensate in a ZnO microwire
Authors: Liaoxin Sun, Shulin Sun, Hongxing Dong, Wei Xie, M. Richard, Lei Zhou,
L. S. Dang, Xuechu Shen, Zhanghai Chen
Categories: cond-mat.mes-hall
Comments: 18 pages, 4 figures
\\
A cavity-polariton, formed due to the strong coupling between exciton and
cavity mode, is one of the most promising composite bosons for realizing
macroscopic spontaneous coherence at high temperature. Up to date, most of
polariton quantum degeneracy experiments were conducted in the complicated
two-dimensional (2D) planar microcavities. The role of dimensionality in
coherent quantum degeneracy of a composite bosonic system of exciton polaritons
remains mysterious. Here we report the first experimental observation of a
one-dimensional (1D) polariton condensate in a ZnO microwire at room
temperature. The massive occupation of the polariton ground state above a
distinct pump power threshold is clearly demonstrated by using the angular
resolved spectroscopy under non-resonant excitation. The power threshold is one
order of magnitude lower than that of Mott transition. Furthermore, a
well-defined far field emission pattern from the polariton condensate mode is
observed, manifesting the coherence build-up in the condensed polariton system.
\\ ( http://arxiv.org/abs/1007.4686 , 1217kb)
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arXiv:1007.4717
Date: Tue, 27 Jul 2010 13:37:57 GMT (482kb)
Title: Dynamics of a cold trapped ion in a Bose-Einstein condensate
Authors: Stefan Schmid, Arne H\"arter, and Johannes Hecker Denschlag
Categories: cond-mat.quant-gas
Comments: 4 pages, 5 figures
\\
We investigate the interaction of a laser-cooled trapped ion (Ba$^+$ or
Rb$^+$) with an optically confined $^{87}$Rb Bose-Einstein condensate (BEC).
The system features interesting dynamics of the ion and the atom cloud as
determined by their collisions and their motion in their respective traps.
Elastic as well as inelastic processes are observed and their respective cross
sections are determined. We demonstrate that a single ion can be used to probe
the density profile of an ultracold atom cloud.
\\ ( http://arxiv.org/abs/1007.4717 , 482kb)
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arXiv:1007.4844
Date: Tue, 27 Jul 2010 23:22:54 GMT (628kb)
Title: Thermodynamics and coherence of a trapped dipolar Fermi gas
Authors: D. Baillie and P. B. Blakie
Categories: cond-mat.quant-gas
Comments: 12 pages, 8 figures
\\
We develop a meanfield treatment of a polarized trapped Fermi gas with
dipole-dipole interactions. Our approach is based on self-consistent
semiclassical Hartree-Fock theory that accounts for direct and exchange
interactions. We discuss our procedure for numerically implementing the
calculation. We study the thermodynamic and the first and second order
correlation properties of the system. We find that the system entropy depends
on the trap geometry, allowing the system to be cooled as the trap aspect ratio
is increased, and that exchange interactions cause the correlation functions to
be anisotropic in the low temperature regime. We also find that many uniform
gas thermodynamic predictions, for which direct interaction effects vanish, are
qualitatively unreliable for trapped systems, most notably for oblate traps. We
develop a simplified Hartree formalism that is applicable to anisotropic
harmonic traps.
\\ ( http://arxiv.org/abs/1007.4844 , 628kb)
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arXiv:1007.4851 (*cross-listing*)
Date: Tue, 27 Jul 2010 23:43:35 GMT (914kb)
Title: Atom chips on direct bonded copper substrates
Authors: Matthew B. Squires, James A. Stickney, Evan J. Carlson, Paul M. Baker,
Walter R. Buchwald, Sandra Wentzell, Steven M. Miller
Categories: physics.ins-det cond-mat.mtrl-sci physics.atom-ph
Comments: 8 pages, 5 figures
\\
We present the use of direct bonded copper (DBC) for the straightforward
fabrication of high power atom chips. Atom chips using DBC have several
benefits: excellent copper/substrate adhesion, high purity, thick (> 100
microns) copper layers, high substrate thermal conductivity, high aspect ratio
wires, the potential for rapid (< 8 hr) fabrication, and three dimensional atom
chip structures. Two mask options for DBC atom chip fabrication are presented,
as well as two methods for etching wire patterns into the copper layer. The
wire aspect ratio that optimizes the magnetic field gradient as a function of
power dissipation is determined to be 0.84:1 (height:width). The optimal wire
thickness as a function of magnetic trapping height is also determined. A test
chip, able to support 100 A of current for 2 s without failing, is used to
determine the thermal impedance of the DBC. An assembly using two DBC atom
chips to provide magnetic confinement is also shown.
\\ ( http://arxiv.org/abs/1007.4851 , 914kb)
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arXiv:1007.4852
Date: Tue, 27 Jul 2010 23:47:04 GMT (134kb)
Title: Possibility of "magic" co-trapping of two atomic species in optical
lattices
Authors: Muir J. Morrison, V. A. Dzuba, A. Derevianko
Categories: physics.atom-ph
Comments: 5 pages, 2 figures, 1 table
\\
Much effort has been devoted to removing differential Stark shifts for atoms
trapped in specially tailored "magic" optical lattices, but thus far work has
focused on a single trapped atomic species. In this work, we extend these ideas
to include two atomic species sharing the same optical lattice. We show
qualitatively that, in particular, scalar J = 0 divalent atoms paired with
non-scalar state atoms have the necessary characteristics to achieve such Stark
shift cancellation. We then present numerical results on "magic" trapping
conditions for 27Al paired with 87Sr, as well as several other divalent atoms.
\\ ( http://arxiv.org/abs/1007.4852 , 134kb)
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arXiv:1007.4877
Date: Wed, 28 Jul 2010 06:44:34 GMT (1006kb)
Title: Observation of universal behaviour of ultracold quantum critical gases
Authors: Hongwei Xiong, Xinzhou Tan, Bing Wang, Lijuan Cao, Baolong L\"u
Categories: cond-mat.quant-gas quant-ph
Comments: 7 pages, 6 figures
\\
Quantum critical matter has already been studied in many systems, including
cold atomic gases. We report the observation of a universal behaviour of
ultracold quantum critical Bose gases in a one-dimensional optical lattice. In
the quantum critical region above the Berezinskii-Kosterlitz-Thouless
transition, the relative phase fluctuations between neighboring subcondensates
and spatial phase fluctuations of quasi-2D subcondensates coexist. We study the
density probability distribution function when both these two phase
fluctuations are considered. A universal exponential density probability
distribution is demonstrated experimentally, which agrees well with a simple
theoretical model by considering these two phase fluctuations.
\\ ( http://arxiv.org/abs/1007.4877 , 1006kb)
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arXiv:1007.4926
Date: Wed, 28 Jul 2010 11:04:55 GMT (201kb)
Title: Critical Exponents and Universality in Bose-Einstein Condensation
Authors: Sanchari Goswami, Tapan Kumar Das and Anindya Biswas
Categories: cond-mat.quant-gas
\\
We report calculation of critical exponents corresponding to three
thermodynamic func- tions, viz. chemical potential, condensate fraction and
specific heat of a non-interacting Bose gas confined in an isotropic harmonic
oscillator trap in one-, two- and three- dimensions. Critical exponents are
also calculated for bosons interacting through van der Waals potential and
confined in a three-dimensional harmonic trap. These expo- nents are found to
be independent of the size of the system and whether the bosons are interacting
or not, demonstrating their universality property. We also find that a
continuous phase transition occurs even in one-dimension, as shown by a rapid
change of the thermodynamic functions at the critical point. This is in sharp
contrast with the result found in the text book treatment of replacing the sum
over occupations of discrete states by an integral. The two- and
three-dimensional results agree with the well known results in the
thermodynamic limit, i.e. when the number of bosons in the trap approaches
infinity. In the same limit, the criticality disappears for the one-dimensional
trap, which again agrees with the standard result.
\\ ( http://arxiv.org/abs/1007.4926 , 201kb)
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arXiv:1007.4927
Date: Wed, 28 Jul 2010 11:13:13 GMT (50kb)
Title: The 17/5 spectrum of the Kelvin-wave cascade
Authors: Evgeny Kozik and Boris Svistunov
Categories: cond-mat.other physics.flu-dyn
Comments: 2 pages, 1 figure
\\
Direct numeric simulation of the Biot-Savart equation readily resolves the
17/5 spectrum of the Kelvin-wave cascade from the 11/3 spectrum of the
non-local (in the wavenumber space) cascade scenario by L'vov and Nazarenko.
This result is a clear-cut visualisation of the unphysical nature of the 11/3
solution, which was established earlier on the grounds of symmetry.
\\ ( http://arxiv.org/abs/1007.4927 , 50kb)
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arXiv:1007.4947
Date: Wed, 28 Jul 2010 12:42:24 GMT (2124kb)
Title: Counterflow induced modulational instability in miscible, two-component
Bose-Einstein condensates
Authors: M. A. Hoefer, C. Hamner, J.J. Chang, and P. Engels
Categories: cond-mat.quant-gas
Comments: 5 pages, 4 figures
\\
Modulational instability (MI) due to relative motion of two superfluids is
found for a miscible, binary Bose-Einstein condensate (BEC). For sufficiently
large relative speeds of the BEC components, we experimentally observe the
onset of counterflow induced MI leading to the proliferation of dark-dark
vector solitons which can experience a transverse (snake) instability. This is
in contrast to nonlinear self-steepening and intercomponent shock formation
previously observed at low counterflow speeds. Our experimental results are
complemented by a linear stability analysis and by multi-dimensional numerical
simulations that reveal an intriguing dynamical richness of the superfluid
counterflow.
\\ ( http://arxiv.org/abs/1007.4947 , 2124kb)
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arXiv:1007.4953
Date: Wed, 28 Jul 2010 13:06:57 GMT (765kb,D)
Title: Route to turbulence in Bose-Einstein Condensate: Evolution of spatial
structures
Authors: J. A. Seman, E. A. L. Henn, R. F. Shiozaki, G. Roati, F. J.
Poveda-Cuevas, K. M. F. Magalh\~aes, V. I. Yukalov, M. Tsubota, M. Kobayashi,
K. Kasamatsu and V. S. Bagnato
Categories: cond-mat.quant-gas
Comments: 6 pages, 5 figures
\\
We have studied a Bose-Einstein condensate of $^{87}Rb$ atoms under an
oscillatory excitation. For a fixed value of the frequency of the oscillation,
we observed the formation of different structures in the cloud as a function of
two parameters: time and amplitude of the excitation. Our results can be
summarized in a diagram of amplitude versus time, in which we identify four
zones where the quantum sample exhibits fundamentally different behaviors. We
concentrate on the regimes generated by the large values of the time and/or
amplitude of the excitation, which we have identified as the turbulent and
granular regimes. The quantum turbulent regime consists in the appearance of a
vortex tangle array in the sample. Together with the experimental observations,
we also present simulations based on the Gross-Pitaevskii equation. The
numerical results show the overall behavior of the diagram, supporting our
experimental observations. When the largest values of the parameters of the
excitation were employed, a granulation of the fluid was observed.
\\ ( http://arxiv.org/abs/1007.4953 , 765kb)
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arXiv:1007.5061
Date: Wed, 28 Jul 2010 20:00:03 GMT (211kb)
Title: Superfluidity and dimerization in a multilayered system of fermionic
polar molecules
Authors: Andrew C. Potter, Erez Berg, Daw-Wei Wang, Bertrand I. Halperin,
Eugene Demler
Categories: cond-mat.quant-gas
Comments: 4+epsilon pages
\\
We consider a layered system of fermionic molecules with permanent dipole
moments aligned by an external field. The dipole interactions between fermions
in adjacent layers are attractive and induce inter-layer pairing. Due to
competition for pairing among adjacent layers, the mean-field ground state of
the layered system is a dimerized superfluid, with pairing only between
every-other layer. We construct an effective Ising-XY lattice model that
describes the interplay between dimerization and superfluid phase fluctuations.
In addition to the dimerized superfluid ground state, and hightemperature
normal state, at intermediate temperature, we find an unusual dimerized
"pseudogap" state with only short-range phase coherence. We propose light
scattering experiments to detect dimerization.
\\ ( http://arxiv.org/abs/1007.5061 , 211kb)
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arXiv:1007.5223
Date: Thu, 29 Jul 2010 14:15:20 GMT (183kb,D)
Title: Bosonic Dynamical Mean-Field Theory
Authors: Michiel Snoek and Walter Hofstetter
Categories: cond-mat.quant-gas
Comments: Chapter to appear in "Non-Equilibrium Quantum Gases at Finite
Temperatures" edited by Nick Proukakis, Simon Gardiner, Matt Davis, Nicolai
Nygaard and Marzena Szymanska, to be published by World Scientific Press
\\
We derive the Bosonic Dynamical Mean-Field equation for bosonic atoms in
optical lattices with arbitrary lattice geometry. The equations are presented
as a systematic expansion in 1/z, z being the number of lattice neighbors.
Hence the theory is applicable in sufficiently high dimensional lattices. We
apply the method to a two-component mixture, for which a rich phase diagram
with spin-order is revealed.
\\ ( http://arxiv.org/abs/1007.5223 , 183kb)
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arXiv:1007.5251
Date: Thu, 29 Jul 2010 15:59:39 GMT (405kb)
Title: Exotic paired phases in ladders with spin-dependent hopping
Authors: Adrian E. Feiguin and Matthew P. A. Fisher
Categories: cond-mat.str-el
Comments: 10 pages, 12 figures
\\
Fermions in two-dimensions (2D) when subject to anisotropic spin-dependent
hopping can potentially give rise to unusual paired states in {\it unpolarized}
mixtures that can behave as non-Fermi liquids. One possibility is a fully
paired state with a gap for fermion excitations in which the Cooper pairs
remain uncondensed. Such a ``Cooper-pair Bose-metal" phase would be expected to
have a singular Bose-surface in momentum space. As demonstrated in the context
of 2D bosons hopping with a frustrating ring-exchange interaction, an analogous
Bose-metal phase has a set of quasi-1D descendent states when put on a ladder
geometry. Here we present a density matrix renormalization group (DMRG) study
of the attractive Hubbard model with spin-dependent hopping on a two-leg ladder
geometry. In our setup, one spin species moves preferentially along the leg
direction, while the other does so along the rung direction. We find compelling
evidence for the existence of a novel Cooper-pair Bose-metal phase in a region
of the phase diagram at intermediate coupling. We further explore the phase
diagram of this model as a function of hopping anisotropy, density, and
interaction strength, finding a conventional superfluid phase, as well as a
phase of paired Cooper pairs with d-wave symmetry, similar to the one found in
models of hard-core bosons with ring-exchange. We argue that simulating this
model with cold Fermi gases on spin dependent optical lattices is a promising
direction for realizing exotic quantum states.
\\ ( http://arxiv.org/abs/1007.5251 , 405kb)
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arXiv:1007.5306 (*cross-listing*)
Date: Thu, 29 Jul 2010 19:44:51 GMT (3069kb,D)
Title: Thermalization of Interacting Fermions and Delocalization in Fock space
Authors: Clemens Neuenhahn and Florian Marquardt
Categories: cond-mat.stat-mech quant-ph
Comments: 4 pages, 4 figures
\\
By means of exact diagonalization, we investigate the onset of 'eigenstate
thermalization' and the crossover to ergodicity in a system of 1D fermions with
increasing interaction. We show that the fluctuations in the expectation values
of the momentum distribution from eigenstate to eigenstate decrease with
increasing coupling strength and system size. It turns out that these
fluctuations are proportional to the inverse participation ratio of eigenstates
represented in the Fock basis. We demonstrate that eigenstate thermalization
should set in even for vanishingly small perturbations in the thermodynamic
limit.
\\ ( http://arxiv.org/abs/1007.5306 , 3069kb)
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arXiv:1005.0461
replaced with revised version Mon, 26 Jul 2010 23:49:12 GMT (70kb)
Title: Super-Tonks-Girardeau gas of spin-1/2 interacting fermions
Authors: Liming Guan and Shu Chen
Categories: cond-mat.quant-gas
Comments: 4 pages, 5 figures
\\ ( http://arxiv.org/abs/1005.0461 , 70kb)
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arXiv:1005.0656
replaced with revised version Wed, 28 Jul 2010 00:37:23 GMT (839kb)
Title: Metastable Quantum Phase Transitions in a One-Dimensional Bose Gas
Authors: Lincoln D. Carr, Rina Kanamoto, and Masahito Ueda
Categories: cond-mat.quant-gas cond-mat.mes-hall
Comments: 29 pages, 12 figures, book will appear later this year; v2 is in
improved format and includes small corrections for final version
Journal-ref: Chap. 13 in "Understanding Quantum Phase Transitions", ed. Lincoln
D. Carr (Taylor & Francis, Boca Raton, Florida, 2010)
\\ ( http://arxiv.org/abs/1005.0656 , 839kb)
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arXiv:1004.4134
replaced with revised version Wed, 28 Jul 2010 16:20:54 GMT (231kb)
Title: Oscillating solitons in a three component BEC
Authors: Piotr Szankowski, Eryk Infeld, Marek Trippenbach, George Rowlands
Categories: cond-mat.quant-gas
Comments: 5 pages, 4 figures
\\ ( http://arxiv.org/abs/1004.4134 , 231kb)
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\\
arXiv:1006.3799 (*cross-listing*)
replaced with revised version Thu, 29 Jul 2010 05:36:38 GMT (2985kb,D)
Title: Single-Atom Resolved Fluorescence Imaging of an Atomic Mott Insulator
Authors: Jacob F. Sherson, Christof Weitenberg, Manuel Endres, Marc Cheneau,
Immanuel Bloch, Stefan Kuhr
Categories: cond-mat.quant-gas quant-ph
\\ ( http://arxiv.org/abs/1006.3799 , 2985kb)
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\\
arXiv:0912.2587
replaced with revised version Thu, 29 Jul 2010 08:18:51 GMT (688kb)
Title: Dynamics of interacting atoms in driven tilted optical lattices
Authors: Andrey R. Kolovsky and Hans J\"urgen Korsch
Categories: quant-ph cond-mat.quant-gas
Comments: 8 pages, 11 figures
Journal-ref: Journal of Siberian Federal University: Mathematics & Physics {\bf
3}, 311 (2010)
\\ ( http://arxiv.org/abs/0912.2587 , 688kb)
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\\
arXiv:1007.1657 (*cross-listing*)
replaced with revised version Thu, 29 Jul 2010 19:08:41 GMT (102kb,D)
Title: Driving quantized vortices with quantum vacuum fluctuations
Authors: Fran\c{c}ois Impens, Ana M. Contreras-Reyes, Paulo A. Maia Neto, Diego
A. R. Dalvit, Romain Gu\'erout, Astrid Lambrecht, Serge Reynaud
Categories: cond-mat.quant-gas physics.atom-ph quant-ph
Comments: 4 pages, 2 figures. Minor correction in the second figure
\\ ( http://arxiv.org/abs/1007.1657 , 102kb)
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Till next time,
Matt.
--
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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/
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http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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Received on Wed Oct 20 2010 - 09:28:34 EST
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