From: Matthew Davis <mdavis_at_physics.uq.edu.au>

Date: Sun, 17 Oct 2010 23:06:27 +1000

Date: Sun, 17 Oct 2010 23:06:27 +1000

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.

-- ========================================================================= Dr M. J. Davis, Associate Professor in Physics School of Mathematics and Physics, ph : +61 7 334 69824 The University of Queensland, fax : +61 7 336 51242 Brisbane, QLD 4072, mdavis_at_physics.uq.edu.au Australia. www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland ========================================================================= _______________________________________________ Matts-arxiv mailing list Matts-arxiv_at_lists.sps.uq.edu.auReceived on Wed Oct 20 2010 - 09:28:34 EST

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