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

Date: Sun, 20 Sep 2009 10:18:57 +1000

Date: Sun, 20 Sep 2009 10:18:57 +1000

Dear subscribers,

Andy Ferris compiled this week's abstracts. There are 29 new preprints and 5

replacements.

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arXiv:0908.3015

Date: Thu, 20 Aug 2009 21:00:00 GMT (673kb)

Title: Universal Thermometry for Trapped Quantum Gases Based on Number

Fluctuations

Authors: Qi Zhou and Tin-Lun Ho

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures

\\

We show that by using a generalized of fluctuation-dissipation theorem, one

can determine the temperature of a trapped quantum gases (with or without

optical lattice) by number fluctuations in the interior of the gas. We show

that this scheme is fast convergent, requiring averaging over 50 samples to

achieve 3% accuracy. Moreover, the accuracy of the scheme is unaffected by the

presence of photon shot noise. This method also enables one to map out magnetic

susceptibility of spin systems as a function of chemical potential and

temperature.

\\ ( http://arxiv.org/abs/0908.3015 , 673kb)

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arXiv:0908.3033

Date: Fri, 21 Aug 2009 07:44:57 GMT (2763kb)

Title: Intrinsic instability at the Bose-Einstein condensation of bosonic

quasiparticles in magnetic insulators

Authors: A. Schilling

Categories: cond-mat.str-el cond-mat.quant-gas

Comments: 10 figures, 74 references

\\

Starting from a phenomenological standard energy functional to describe the

condensation of a dilute gas of bosonic quasiparticles in magnetic insulators,

we find that the inclusion of a perturbation term that explicitly violates the

axial symmetry significantly modifies the details of the resulting Bose

Einstein condensation. Systems with an originally axial symmetry must show an

intrinsic tendency to spontaneously violate this symmetry as soon as the

condensation sets in, and the phase transition at the respective critical field

may even become of first order. We can explain a number of features in the

experimental data of various insulating spin systems, such as a slightly

nonlinear magnetization near the critical field as well as hysteresis effects

and peculiarities in the energy-level scheme of TlCuCl3. We also offer a

consistent explanation for certain anomalies in the magnetocaloric effect and

in the magnetization of BaCuSi2O6 by assuming a spontaneous violation of axial

symmetry at the magnetic phase transition on an energy scale of about 1

micro-eV. The resulting anisotropy gap in the magnetic excitation spectrum,

that inevitably forms at the critical field of all such systems, lifts the

linear Goldstone mode and is therefore seriously limiting the lifetime of

magnetic condensates to a few nanoseconds at most.

\\ ( http://arxiv.org/abs/0908.3033 , 2763kb)

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arXiv:0908.3040

Date: Fri, 21 Aug 2009 01:48:20 GMT (541kb)

Title: Bose-Einstein condensation of trapped polaritons in 2D electron-hole

systems in a high magnetic field

Authors: Oleg L. Berman, Roman Ya. Kezerashvili, and Yurii E. Lozovik

Categories: cond-mat.mes-hall cond-mat.str-el

Comments: 16 pages, 6 figures. accepted in Physical Review B

\\

The Bose-Einstein condensation (BEC) of magnetoexcitonic polaritons in

two-dimensional (2D) electron-hole system embedded in a semiconductor

microcavity in a high magnetic field $B$ is predicted. There are two physical

realizations of 2D electron-hole system under consideration: a graphene layer

and quantum well (QW). A 2D gas of magnetoexcitonic polaritons is considered in

a planar harmonic potential trap. Two possible physical realizations of this

trapping potential are assumed: inhomogeneous local stress or harmonic electric

field potential applied to excitons and a parabolic shape of the semiconductor

cavity causing the trapping of microcavity photons. The effective Hamiltonian

of the ideal gas of cavity polaritons in a QW and graphene in a high magnetic

field and the BEC temperature as functions of magnetic field are obtained. It

is shown that the effective polariton mass $M_{\rm eff}$ increases with

magnetic field as $B^{1/2}$. The BEC critical temperature $T_{c}^{(0)}$

decreases as $B^{-1/4}$ and increases with the spring constant of the parabolic

trap. The Rabi splitting related to the creation of a magnetoexciton in a high

magnetic field in graphene and QW is obtained. It is shown that Rabi splitting

in graphene can be controlled by the external magnetic field since it is

proportional to $B^{-1/4}$, while in a QW the Rabi splitting does not depend on

the magnetic field when it is strong.

\\ ( http://arxiv.org/abs/0908.3040 , 541kb)

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arXiv:0908.3046

Date: Fri, 21 Aug 2009 04:38:46 GMT (64kb,D)

Title: Spin gradient thermometry for ultracold atoms in optical lattices

Authors: David M. Weld, Patrick Medley, Hirokazu Miyake, David Hucul, David E.

Pritchard, Wolfgang Ketterle

Categories: cond-mat.quant-gas

Comments: 5 pages, 3 figures

\\

We demonstrate spin gradient thermometry, a new general method of measuring

the temperature of ultracold atoms in optical lattices. We realize a mixture of

spins separated by a magnetic field gradient. Measurement of the width of the

transition layer between the two spin domains serves as a new method of

thermometry which is observed to work over a broad range of lattice depths and

temperatures, including in the Mott insulator regime. We demonstrate the

thermometry in a system of ultracold rubidium atoms. The lowest measured

temperature is 1 nK, indicating that the system has reached the quantum regime,

where insulating shells are separated by superfluid layers.

\\ ( http://arxiv.org/abs/0908.3046 , 64kb)

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arXiv:0908.3052

Date: Fri, 21 Aug 2009 04:40:32 GMT (441kb)

Title: Quantitative test of mean-field description of a trapped two-dimensional

Bose gas

Authors: R. N. Bisset and P. B. Blakie

Categories: cond-mat.quant-gas

Comments: 5 pages, 2 figures, 1 table

\\

We investigate the accuracy of two mean-field theories of the trapped

two-dimensional Bose gas at predicting transition region properties by

comparison to non-perturbative c-field calculations. To make these comparisons

we examine the density profiles and the predictions for the

Berezinskii-Kosterlitz-Thouless superfluid transition temperature over a

parameter range in which the degree of thermal activation in the tightly

trapped direction varies considerably. These results present an important test

of these mean-field theories, and provide a characterization of their typical

accuracy.

\\ ( http://arxiv.org/abs/0908.3052 , 441kb)

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arXiv:0908.3074

Date: Fri, 21 Aug 2009 08:33:54 GMT (350kb)

Title: The BCS-BEC crossover and the disappearance of FFLO-correlations in a

spin-imbalanced, one-dimensional Fermi gas

Authors: F. Heidrich-Meisner. A.E. Feiguin, U. Schollwoeck, W. Zwerger

Categories: cond-mat.quant-gas cond-mat.supr-con

Comments: 13 pages, 21 eps figures

\\

We present a numerical study of the one-dimensional BCS-BEC crossover of a

spin-imbalanced Fermi gas. The crossover is described by the Bose-Fermi

resonance model in a real space representation. Our main interest is in the

behavior of the pair correlations, which, in the BCS limit, are of the

Fulde-Ferrell-Larkin-Ovchinnikov type, while in the BEC limit, a superfluid of

diatomic molecules forms that exhibits quasi-condensation at zero momentum. We

use the density matrix renormalization group method to compute the phase

diagram as a function of the detuning of the molecular level and the

polarization. As a main result, we show that FFLO-like correlations disappear

well below full polarization close to the resonance. The critical polarization

depends on both the detuning and the filling.

\\ ( http://arxiv.org/abs/0908.3074 , 350kb)

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arXiv:0908.3110

Date: Fri, 21 Aug 2009 19:54:59 GMT (274kb)

Title: Detection of Fermi Pairing via Electromagnetically Induced Transparency

Authors: Lei Jiang, Han Pu, Weiping Zhang, and Hong Y. Ling

Categories: cond-mat.quant-gas cond-mat.other

Comments: 8 pages, 2 figures, to appear in Phys. Rev. A

\\

An optical spectroscopic method based on the principle of

electromagnetically-induced transparency (EIT) is proposed as quite a generic

probing tool that provides valuable insights into the nature of Fermi paring in

ultracold Fermi gases of two hyperfine states. This technique has the

capability of allowing spectroscopic response to be determined in a nearly

non-destructive manner and the whole spectrum may be obtained by scanning the

probe laser frequency faster than the lifetime of the sample without

re-preparing the atomic sample repeatedly. A quasiparticle picture is

constructed to facilitate a simple physical explanation of the pairing

signature in the EIT spectra.

\\ ( http://arxiv.org/abs/0908.3110 , 274kb)

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arXiv:0908.3179

Date: Fri, 21 Aug 2009 18:52:26 GMT (139kb)

Title: Ion induced density bubble in a strongly correlated one dimensional gas

Authors: J. Goold, H. Doerk-Bending, T. Calarco, Th. Busch

Categories: cond-mat.quant-gas quant-ph

Comments: 5 pages, 3 figures

\\

We consider a harmonically trapped Tonks-Girardeau gas of impenetrable bosons

in the presence of a single embedded ion, which is assumed to be tightly

confined in a RF trap. In an ultracold ion-atom collision the ion's charge

induces an electric dipole moment in the atoms which leads to an attractive

$r^{-4}$ potential at large distances. We treat the ion as a deformation of the

harmonic trap potential and model its short range interaction with the gas in

the framework of quantum defect theory. The molecular bound states of the ionic

potential are not populated due to the lack of any possible relaxation process

in the Tonks-Girardeau regime. Armed with this knowledge we calculate the

density profile of the gas in the presence of a central ionic impurity and show

that a density \textit{bubble} of the order of a micron occurs around the ion

for typical experimental parameters. From these exact results we show that an

ionic impurity in a Tonks gas can be described using a pseudopotential,

allowing for significantly easier treatment.

\\ ( http://arxiv.org/abs/0908.3179 , 139kb)

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arXiv:0908.3012

Date: Fri, 21 Aug 2009 18:53:11 GMT (2962kb)

Title: Classical phases and quantum angles in the description of interfering

Bose-Einstein condensates

Authors: W. J. Mullin and F. Lalo\"e

Categories: quant-ph

Comments: 35 pages, 22 figures

\\

The interference of two Bose-Einstein condensates, initially in Fock states,

can be described in terms of their relative phase, treated as a random unknown

variable. This phase can be understood, either as emerging from the

measurements, or preexisting to them; in the latter case, the originating

states could be phase states with unknown phases, so that an average over all

their possible values is taken. Both points of view lead to a description of

probabilities of results of experiments in terms of a phase angle, which plays

the role of a classical variable. Nevertheless, in some situations, this

description is not sufficient: another variable, which we call the "quantum

angle", emerges from the theory. This article studies various manifestations of

the quantum angle. We first introduce the quantum angle by expressing two Fock

states crossing a beam splitter in terms of phase states, and relate the

quantum angle to off-diagonal matrix elements in the phase representation. Then

we consider an experiment with two beam splitters, where two experimenters make

dichotomic measurements with two interferometers and detectors that are far

apart; the results lead to violations of the Bell-Clauser-Horne-Shimony-Holt

inequality (valid for local-realistic theories, including classical

descriptions of the phase). Finally, we discuss an experiment where particles

from each of two sources are either deviated via a beam splitter to a side

collector or proceed to the point of interference. For a given interference

result, we find "population oscillations" in the distributions of the deviated

particles, which are entirely controlled by the quantum angle. Various versions

of population oscillation experiments are discussed, with two or three

independent condensates.

\\ ( http://arxiv.org/abs/0908.3012 , 2962kb)

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arXiv:0908.2815 (*cross-listing*)

Date: Wed, 19 Aug 2009 20:20:01 GMT (40kb)

Title: Semirelativistic N-boson systems bound by attractive pair potentials

Authors: Richard L. Hall, Wolfgang Lucha

Categories: math-ph hep-ph math.MP quant-ph

Comments: 12 pages, 2 figures

Report-no: CUQM - 131; HEPHY - PUB 879/09

\\

We establish bounds on the energy of a system of N identical bosons bound by

attractive pair potentials and obeying the semirelativistic Salpeter equation.

The lower bound is provided by a `reduction', with the aid of Jacobi relative

coordinates, to a suitably scaled one-body Klein-Gordon problem. Complementary

upper energy bounds are provided by means of a Gaussian trial function.

Detailed results are presented for the exponential pair potential V(r) =

-v\exp(-r/a).

\\ ( http://arxiv.org/abs/0908.2815 , 40kb)

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arXiv:0908.3147

Date: Fri, 21 Aug 2009 15:15:06 GMT (181kb)

Title: Decoherence and Collisional Frequency Shifts of Trapped Bosons and

Fermions

Authors: Kurt Gibble

Categories: physics.atom-ph

Comments: To appear in PRL

\\

We perform exact calculations of collisional frequency shifts for several

fermions or bosons using a singlet and triplet basis for pairs of particles.

The "factor of 2 controversy" for bosons becomes clear - the factor is always

2. Decoherence is described by singlet states and they are unaffected by

spatially uniform clock fields. Spatial variations are critical, especially for

fermions which were previously thought to be immune to collision shifts. The

spatial variations lead to decoherence and a novel frequency shift that is not

proportional to the partial density of internal states.

\\ ( http://arxiv.org/abs/0908.3147 , 181kb)

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arXiv:0908.3188

Date: Fri, 21 Aug 2009 21:49:09 GMT (304kb)

Title: Quantum quenches and thermalization in one-dimensional fermionic systems

Authors: Marcos Rigol

Categories: cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el

Comments: 12 pages, 12 figures

\\

We study the dynamics and thermalization of strongly correlated fermions in

finite one-dimensional lattices after a quantum quench. Our calculations are

performed using exact diagonalization. We focus on one- and two-body

observables such as the momentum distribution function [n(k)] and the

density-density structure factor [N(k)], respectively, and study the effects of

approaching an integrable point. We show that while the relaxation dynamics and

thermalization of N(k) for fermions is very similar to the one of hardcore

bosons, the behavior of n(k) is distinctively different. The latter observable

exhibits a slower relaxation dynamics in fermionic systems. We identify the

origin of this behavior, which is related to the off-diagonal matrix elements

of n(k) in the basis of the eigenstates of the Hamiltonian. More generally, we

find that thermalization occurs far away from integrability and that it breaks

down as one approaches the integrable point.

\\ ( http://arxiv.org/abs/0908.3188 , 304kb)

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arXiv:0908.3235

Date: Mon, 24 Aug 2009 19:35:40 GMT (227kb)

Title: An atomic colour superfluid via three-body loss

Authors: A. Kantian, M. Dalmonte, S. Diehl, W. Hofstetter, P. Zoller, A. J.

Daley

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures

\\

Large three-body losses in a three-component Fermi gas confined in an optical

lattice can prevent the occupation of a lattice site by three atoms. This

effective constraint not only gives rise to a suppression of actual three-body

loss, but stabilises BCS pairing phases by suppressing the formation of trions.

We study the effects of the constraint using bosonisation and density matrix

renormalisation group techniques (DMRG). We discuss the case of lithium

experiments, and study the dissipative dynamics including loss using

time-dependent DMRG with quantum trajectories methods.

\\ ( http://arxiv.org/abs/0908.3235 , 227kb)

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arXiv:0908.3260

Date: Sat, 22 Aug 2009 15:57:34 GMT (282kb,D)

Title: Non classical velocity statistics in a turbulent atomic Bose Einstein

condensate

Authors: Angela White, Nick P. Proukakis and Carlo F. Barenghi

Categories: cond-mat.quant-gas cond-mat.other

Comments: 10 pages, 3 figures

\\

In a recent experiment Paoletti et al (Phys. Rev. Lett. 101, 154501, 2008)

monitored the motion of tracer particles in turbulent superfluid helium and

inferred that the velocity components do not obey the Gaussian statistics

observed in ordinary turbulence. Motivated by their experiment, we create a

small turbulent state in an atomic Bose-Einstein condensate, which enables us

to compute directly the velocity field, and we find similar non-classical

power-law tails. Our result thus suggests that non-Gaussian turbulent velocity

statistics describe a fundamental property of quantum fluids. We also track the

decay of the vortex tangle in the presence of the thermal cloud.

\\ ( http://arxiv.org/abs/0908.3260 , 282kb)

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arXiv:0908.3356

Date: Mon, 24 Aug 2009 03:08:35 GMT (1522kb)

Title: Quantum Information Approach to Rotating Bose-Einstein Condensate

Authors: Zhao Liu, Hongli Guo, Shu Chen and Heng Fan

Categories: cond-mat.quant-gas quant-ph

Comments: 4 pages, 6 figures

\\

We investigate the 2D weakly interacting Bose-Einstein condensate in a

rotating trap by the tools of quantum information theory. The critical

exponents of the ground state fidelity susceptibility and the correlation

length of the system are obtained for the quantum phase transition when the

frst vortex is formed. We also find the single-particle entanglement can be an

indicator of the angular momentums for some real ground states. The

single-particle entanglement of fractional quantum Hall states such as Laughlin

state and Pfaffian state is also studied.

\\ ( http://arxiv.org/abs/0908.3356 , 1522kb)

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arXiv:0908.3204

Date: Fri, 21 Aug 2009 20:42:48 GMT (23kb)

Title: Collisional decoherence of internal state superpositions in a trapped

ultracold gas

Authors: C. J. Hemming and R. V. Krems

Categories: quant-ph

Comments: 20 pages, 1 figure

\\

We analyze the temperature-dependent rate of decoherence of superpositions of

internal states of trapped molecules due to collisions with ultracold buffer

gas particles. Our analysis is applicable for an arbitrary bath/tracer particle

mass ratio. Both elastic and inelastic collisions contribute to decoherence. We

obtain an expression relating the observable decoherence rate to pairwise

scattering properties, specifically the scattering lengths and low-temperature

cross-sections. We consider the dependence on the bath/tracer particle mass

ratio for the case of light bath and heavy tracer particles. The expressions

obtained may be useful in low-temperature applications where accurate estimates

of decoherence rates are desirable. The results suggest a method for

determining the scattering lengths of atoms and molecules in different internal

states by measuring decoherence-induced damping of coherent oscillations.

\\ ( http://arxiv.org/abs/0908.3204 , 23kb)

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arXiv:0908.3483

Date: Tue, 25 Aug 2009 19:34:28 GMT (504kb,D)

Title: Non-equilibrium dynamics of interacting Fermi systems in quench

experiments

Authors: Mehrtash Babadi, David Pekker, Rajdeep Sensarma, Antoine Georges,

Eugene Demler

Categories: cond-mat.quant-gas cond-mat.str-el

Comments: 4 Pages, 2 Figs

\\

We describe the dynamics of two component non-interacting ultracold Fermions

which are initially in thermal equilibrium and undergo a rapid quench to either

the repulsive or attractive side of a Feshbach resonance. The short time

dynamics is dominated by the exponentially growing collective modes. We study

the Stoner instability and formation of ferromagnetic textures on the repulsive

side, and the pairing instability towards BCS or FFLO-like states (determined

by the population imbalance) on the attractive side. In each case, we evaluate

the growth rate of unstable modes and predict the typical lengthscale of

textures to be formed.

\\ ( http://arxiv.org/abs/0908.3483 , 504kb)

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arXiv:0908.3484

Date: Mon, 24 Aug 2009 20:01:24 GMT (95kb)

Title: Hyperfine Spin-Two (F=2) Atoms in Three-Dimensional Optical Lattices:

Phase Diagrams and Phase Transitions

Authors: Michiel Snoek, Jun Liang Song, and Fei Zhou

Categories: cond-mat.quant-gas

Comments: 10 pages, 10 figures

\\

We consider ultracold matter of spin-2 atoms in optical lattices. We derive

an effective Hamiltonian for the studies of spin ordering in Mott states and

investigate hyperfine spin correlations. Particularly, we diagonalize the

Hamiltonian in an on-site Hilbert space taking into account spin-dependent

interactions and exchange between different sites. We obtain phase diagrams and

quantum phase transitions between various magnetic phases.

\\ ( http://arxiv.org/abs/0908.3484 , 95kb)

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arXiv:0908.3547

Date: Tue, 25 Aug 2009 08:02:36 GMT (76kb)

Title: Quasiparticle excitations in Bose-Fermi mixtures

Authors: Shimul Akhanjee

Categories: cond-mat.quant-gas cond-mat.stat-mech

Comments: 7 pages, eps figures

\\

We analyze the excitation spectrum of a three-dimensional(3D) Bose-Fermi

mixture with tunable resonant interaction parameters. We focus on an attractive

3-particle vertex describing fermionic and bosonic atoms which can scatter to

create fermionic molecules. We demonstrate how this interaction vertex causes

the Lorentzian broadening of an $N_\psi$-fold degenerate molecular Fermi

energy. Mean field equations for a flat, wide atomic dispersion are generated

by a linked cluster expansion and within a Hartree approximation. Beyond mean

field theory, a random phase approximation (RPA) generates a correction to the

bosonic chemical potential at order $1/N_\psi$. The results are expected to be

exact in the limit of infinite degeneracy $N_\psi \to \infty$. We conjecture

that the quasiparticle features of the one level analysis of excitation spectra

apply to the case containing dispersive bands.

\\ ( http://arxiv.org/abs/0908.3547 , 76kb)

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arXiv:0908.3631

Date: Tue, 25 Aug 2009 15:21:28 GMT (900kb,D)

Title: Chiral confinement in quasirelativistic Bose-Einstein condensates

Authors: M. Merkl, A. Jacob, F. E. Zimmer, P. Ohberg and L. Santos

Categories: cond-mat.quant-gas

Comments: 4 pages

\\

In the presence of a laser-induced spin-orbit coupling an interacting ultra

cold spinor Bose-Einstein condensate may acquire a quasi-relativistic character

described by a non-linear Dirac-like equation. We show that as a result of the

spin-orbit coupling and the non-linearity the condensate may become

self-trapped, resembling the so-called chiral confinement, previously studied

in the context of the massive Thirring model. We first consider 1D geometries

where the self-confined condensates present an intriguing sinusoidal dependence

on the inter-particle interactions. We further show that multi-dimensional

chiral-confinement is also possible under appropriate feasible laser

arrangements, and discuss the properties of 2D and 3D condensates, which differ

significantly from the 1D case.

\\ ( http://arxiv.org/abs/0908.3631 , 900kb)

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arXiv:0908.3504

Date: Mon, 24 Aug 2009 21:33:27 GMT (356kb,D)

Title: Macroscopic magnetic guide for cold atoms

Authors: Alexey Tonyushkin and Mara Prentiss

Categories: physics.atom-ph physics.ins-det

\\

We demonstrate a macroscopic magnetic guide for cold atoms, and show the

results of its application to atom interferometry. This guide is based on

copper tape coils that allow the guide to be located more than a cm away from

the surface of the coils; therefore these structures can be placed outside the

vacuum chamber. Compared to a ferromagnetic guide, the new guides offer precise

control over the magnetic field. The guide utilizes symmetric geometry, where

the atoms are located symmetrically between the coils. This geometry has

provided a much lower magnetic field curvature that promises longer coherence

time for atom interferometers.

\\ ( http://arxiv.org/abs/0908.3504 , 356kb)

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arXiv:0908.2447 (*cross-listing*)

Date: Mon, 17 Aug 2009 21:16:48 GMT (62kb,D)

Title: Using Atom Interferometery to Search for New Forces

Authors: Jay G. Wacker

Categories: hep-ph physics.atom-ph

Comments: 5 pages, 2 figures

\\

Atom interferometry is a rapidly advancing field and this Letter proposes an

experiment based on existing technology that can search for new short distance

forces. With current technology it is possible to improve the sensitivity by up

to a factor of 102 and near-future advances will be able to rewrite the limits

for forces with ranges from 100 um to 1 km.

\\ ( http://arxiv.org/abs/0908.2447 , 62kb)

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arXiv:0908.3733

Date: Wed, 26 Aug 2009 06:36:36 GMT (561kb)

Title: Induced interactions and the superfluid transition temperature in a

three-component Fermi gas

Authors: J.-P. Martikainen, J. Kinnunen, P. Torma, C. J. Pethick

Categories: cond-mat.quant-gas cond-mat.supr-con

Comments: 4 pages, 5 figures

Report-no: NORDITA-2009-52

\\

We study many-body contributions to the effective interaction between

fermions in a three-component Fermi mixture. We find that effective

interactions between two components induced by the third component can lead to

a phase diagram different from that predicted if interactions with the third

component are neglected. As a result, in a confining potential a superfluid

shell structure can arise even for equal populations of the components. We

compute the critical temperature for the BCS transition in a three-component

6Li mixture and find that the result can deviate strongly from the reduction of

T_c by a factor 2.22 predicted for a weakly interacting two-component system.

\\ ( http://arxiv.org/abs/0908.3733 , 561kb)

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arXiv:0908.3790

Date: Wed, 26 Aug 2009 10:42:43 GMT (240kb)

Title: Modification of energy shifts of atoms by the presence of a boundary in

a thermal bath and the Casimir-Polder force

Authors: Zhiying Zhu, Hongwei Yu

Categories: quant-ph physics.atom-ph

Comments: 29 pages, 3 figures

Journal-ref: Phys. Rev. A 79, 032902 (2009

DOI: 10.1103/PhysRevA.79.032902

\\

We study the modification by the presence of a plane wall of energy level

shifts of two-level atoms which are in multipolar coupling with quantized

electromagnetic fields in a thermal bath in a formalism which separates the

contributions of thermal fluctuations and radiation reaction and allows a

distinct treatment to atoms in the ground and excited states. The position

dependent energy shifts give rise to an induced force acting on the atoms. We

are able to identify three different regimes where the force shows distinct

features and examine, in all regimes, the behaviors of this force in both the

low temperature limit and the high temperature limit for both the ground state

and excited state atoms, thus providing some physical insights into the

atom-wall interaction at finite temperature. In particular, we show that both

the magnitude and the direction of the force acting on an atom may have a clear

dependence on atomic the polarization directions. In certain cases, a change of

relative ratio of polarizations in different directions may result in a change

of direction of the force.

\\ ( http://arxiv.org/abs/0908.3790 , 240kb)

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arXiv:0908.3791

Date: Wed, 26 Aug 2009 13:12:39 GMT (185kb)

Title: Observation of Electromagnetically Induced Transparency and Slow Light

in the Dark State - Bright State Basis of CPT

Authors: T. Laupr\^etre (LAC), J. Ruggiero (LAC), R. Ghosh (JNU), F. Bretenaker

(LAC), F. Goldfarb (LAC)

Categories: quant-ph

\\

Electromagnetically induced transparency (EIT) is observed in a three-level

system composed of an excited state and two coherent superpositions of the two

ground-state levels. This peculiar ground state basis is composed of the

so-called bright and dark states of the same atomic system in a standard

coherent population trapping configuration. The characteristics of EIT, namely,

width of the transmission window and reduced group velocity of light, in this

unusual basis, are theoretically and experimentally investigated and are shown

to be essentially identical to those of standard EIT in the same system.

\\ ( http://arxiv.org/abs/0908.3791 , 185kb)

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arXiv:0908.3867

Date: Wed, 26 Aug 2009 17:12:34 GMT (43kb,D)

Title: Double humped states in the nonlinear Schroedinger equation with a

random potential

Authors: Hagar Veksler, Yevgeny Krivolapov and Shmuel Fishman

Categories: quant-ph

Comments: 10 pages, 3 figures

\\

The role of double humped states in spreading of wave packets for the

nonlinear Schroedinger equation (NLSE) with a random potential is explored and

the spreading mechanism is unraveled. Comparison with an NLSE with a

double-well potential is made. There are two independent affects of the

nonlinearity on the double humped states for the NLSE: coupling to other states

and destruction. The interplay between these effects is discussed.

\\ ( http://arxiv.org/abs/0908.3867 , 43kb)

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arXiv:0908.3919

Date: Thu, 27 Aug 2009 01:02:29 GMT (31kb)

Title: Particle-Hole Asymmetry and Brightening of Solitons in A Strongly

Repulsive BEC

Authors: Radha Balakrishnan, Indubala I. Satija and Charles W. Clark

Categories: cond-mat.quant-gas

\\

We study solitary wave propagation in the condensate of a system of hard-core

bosons with nearest neighbor interactions. For this strongly repulsive system,

the evolution equation for the condensate order parameter obtained using spin

coherent state averages is different from the usual Gross-Pitaevskii equation

(GPE). The system is found to support two kinds of solitons when there is a

particle-hole imbalance: a gray soliton that dies out as the velocity

approaches the Bogoliubov sound velocity, and a new type of soliton which

brightens and persists all the way up to the sound velocity, transforming into

a periodic wave train at supersonic speed. Analogous to GPE soliton, the

energy-momentum dispersion for both the solitons is characterized by Lieb II

modes.

\\ ( http://arxiv.org/abs/0908.3919 , 31kb)

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\\

arXiv:0908.3686 (*cross-listing*)

Date: Tue, 25 Aug 2009 20:50:33 GMT (225kb)

Title: Hot Topics in Cold Gases

Authors: Robert Seiringer

Categories: math-ph cond-mat.quant-gas math.MP

Comments: Plenary lecture given at the XVI International Congress on

Mathematical Physics, Prague, August 3-8, 2009

\\

Since the first experimental realization of Bose-Einstein condensation in

cold atomic gases in 1995 there has been a surge of activity in this field.

Ingenious experiments have allowed us to probe matter close to zero temperature

and reveal some of the fascinating effects quantum mechanics has bestowed on

nature. It is a challenge for mathematical physicists to understand these

various phenomena from first principles, that is, starting from the underlying

many-body Schr\"odinger equation. Recent progress in this direction concerns

mainly equilibrium properties of dilute, cold quantum gases. We shall explain

some of the results in this article, and describe the mathematics involved in

understanding these phenomena. Topics include the ground state energy and the

free energy at positive temperature, the effect of interparticle interaction on

the critical temperature for Bose-Einstein condensation, as well as the

occurrence of superfluidity and quantized vortices in rapidly rotating gases.

\\ ( http://arxiv.org/abs/0908.3686 , 225kb)

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\\

arXiv:0908.3952

Date: Thu, 27 Aug 2009 08:36:25 GMT (79kb)

Title: Open system effects on slow light and electromagnetically induced

transparency

Authors: Jonas Tidstr\"om, Marie Ericsson, Erik Sj\"oqvist, L. Mauritz

Andersson

Categories: quant-ph

\\

The interaction of a three-level $\Lambda$-system with a Markovian

environment is analyzed. A coherence vector formalism is used and a vector form

of the Lindblad equation is derived. Depolarization, dephasing, and different

amplitude damping channels acting on the subspace of the ground states of the

$\Lambda$-system are investigated. Analytic expressions of the concomitant

optical susceptibility are given in the limit of a small probe field and a

strong control field, and we analyze how the different channels influence the

optical response. For a given group velocity, the absorption depends

non-trivially on the type of open system interaction and even gain can be

obtained.

\\ ( http://arxiv.org/abs/0908.3952 , 79kb)

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The replacements:

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\\

arXiv:0903.5265

replaced with revised version Fri, 21 Aug 2009 09:35:17 GMT (899kb)

Title: Antiferromagnetic Order of Repulsively Interacting Fermions on Optical

lattices

Authors: Tobias Gottwald, Peter van Dongen

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures

\\ ( http://arxiv.org/abs/0903.5265 , 899kb)

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\\

arXiv:0904.0238

replaced with revised version Mon, 24 Aug 2009 15:17:28 GMT (89kb)

Title: Bragg spectroscopy for measuring Casimir-Polder interactions with

Bose-Einstein condensates above corrugated surfaces

Authors: Gustavo A. Moreno, Diego A. R. Dalvit, Esteban Calzetta

Categories: quant-ph

Comments: revised version

\\ ( http://arxiv.org/abs/0904.0238 , 89kb)

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\\

arXiv:0903.3054

replaced with revised version Tue, 25 Aug 2009 07:07:40 GMT (107kb)

Title: Large violation of Wiedemann Franz law in Luttinger liquids

Authors: Arti Garg, David Rasch, Efrat Shimshoni, Achim Rosch

Categories: cond-mat.str-el

Comments: Added reference

Journal-ref: Phys. Rev. Lett. 103, 096402 (2009)

DOI: 10.1103/PhysRevLett.103.096402

\\ ( http://arxiv.org/abs/0903.3054 , 107kb)

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\\

arXiv:0907.2245 (*cross-listing*)

replaced with revised version Wed, 26 Aug 2009 15:40:02 GMT (366kb,D)

Title: Many-body treatment of the collisional frequency shift in fermionic

atoms

Authors: A. M. Rey, A. V. Gorshkov, C. Rubbo

Categories: physics.atom-ph cond-mat.quant-gas cond-mat.str-el quant-ph

Comments: 5 pages, 3 figures. V2: added 1 reference

\\ ( http://arxiv.org/abs/0907.2245 , 366kb)

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\\

arXiv:0906.0014

replaced with revised version Wed, 26 Aug 2009 23:37:01 GMT (520kb)

Title: Renormalization Group for Mixed Fermion-Boson Systems

Authors: Seiji J. Yamamoto and Qimiao Si

Categories: cond-mat.str-el

Comments: (v2) a few points made clearer and some types corrected

\\ ( http://arxiv.org/abs/0906.0014 , 520kb)

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Till next time,

Matt.

-- ========================================================================= Dr M. J. Davis, Associate Professor in Physics School of Mathematics and Physics, ph : +61 7 334 69824 The University of Queensland, fax : +61 7 336 51242 Brisbane, QLD 4072, mdavis_at_physics.uq.edu.au Australia. www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= 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 Thu Sep 24 2009 - 15:47:36 EST

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