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

Date: Tue, 12 Sep 2006 13:35:41 +1000 (EST)

Date: Tue, 12 Sep 2006 13:35:41 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Home page: http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/

Abstracts for this week:

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Paper: cond-mat/0609007

Date: Fri, 1 Sep 2006 01:54:29 GMT (977kb)

Title: Coherence-enhanced imaging of a degenerate Bose gas

Authors: L. E. Sadler, J. M. Higbie, S. R. Leslie, M. Vengalattore, and D. M.

Stamper-Kurn

Comments: 4 pages, 4 figures

Subj-class: Other

\\

We present coherence-enhanced imaging, an in situ technique that uses Raman

superradiance to probe the spatial coherence properties of an ultracold gas.

Applying this method, we obtain a spatially resolved measurement of the

condensate number and more generally, of the first-order spatial correlation

function in a gas of $^{87}$Rb atoms. We observe the enhanced decay of

propagating spin gratings in high density regions of a Bose condensate, a decay

we ascribe to collective, non-linear atom-atom scattering. Further, we directly

observe spatial inhomogeneities that arise generally in the course of extended

sample superradiance.

\\ ( http://arXiv.org/abs/cond-mat/0609007 , 977kb)

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Paper: cond-mat/0609014

Date: Fri, 1 Sep 2006 09:18:48 GMT (317kb)

Title: Condensate splitting in an asymmetric double well for atom chip based

sensors

Authors: B.V.Hall, S.Whitlock, R.Anderson, P.Hannaford and A.Sidorov

Comments: 4 pages, 5 figures

Subj-class: Other

\\

We report on the adiabatic splitting of a BEC of $^{87}$Rb atoms by an

asymmetric double-well potential located above the edge of a perpendicularly

magnetized TbGdFeCo film atom chip. By controlling the barrier height and

double-well asymmetry the sensitivity of the axial splitting process is

investigated through observation of the fractional atom distribution between

the left and right wells. This process constitutes a novel sensor for which we

infer a single shot sensitivity to gravity fields of $\delta

g/g\approx2\times10^{-4}$. From a simple analytic model we propose improvements

to chip-based gravity detectors using this demonstrated methodology.

\\ ( http://arXiv.org/abs/cond-mat/0609014 , 317kb)

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Paper (*cross-listing*): math-ph/0608069

Date: Thu, 31 Aug 2006 15:29:54 GMT (39kb)

Title: Free Energy of a Dilute Bose Gas: Lower Bound

Authors: Robert Seiringer

Comments: LaTeX2e, 53 pages

Subj-class: Mathematical Physics; Statistical Mechanics

\\

A lower bound is derived on the free energy (per unit volume) of a

homogeneous Bose gas at density $\rho$ and temperature $T$. In the dilute

regime, i.e., when $a^3\rho \ll 1$, where $a$ denotes the scattering length of

the pair-interaction potential, our bound differs to leading order from the

expression for non-interacting particles by the term $4\pi a (2\rho^2 -

[\rho-\rho_c]_+^2)$. Here, $\rho_c(T)$ denotes the critical density for

Bose-Einstein condensation (for the non-interacting gas), and $[ ]_+$ denotes

the positive part. Our bound is uniform in the temperature up to temperatures

of the order of the critical temperature, i.e., $T \sim \rho^{2/3}$ or smaller.

One of the key ingredients in the proof is the use of coherent states to extend

the method introduced in [arXiv:math-ph/0601051] for estimating correlations to

temperatures below the critical one.

\\ ( http://arXiv.org/abs/math-ph/0608069 , 39kb)

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Paper: cond-mat/0604184

replaced with revised version Thu, 31 Aug 2006 22:42:48 GMT (29kb)

Title: Two-species fermion mixtures with population imbalance

Authors: M. Iskin and C. A. R. Sa de Melo

Comments: 4 pages with 3 figures, accepted version to PRL

Subj-class: Superconductivity; Other

\\ ( http://arXiv.org/abs/cond-mat/0604184 , 29kb)

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Paper: cond-mat/0608721

replaced with revised version Fri, 1 Sep 2006 15:56:39 GMT (135kb)

Title: Repulsively bound atom pairs: Overview, Simulations and Links

Authors: A. J. Daley, A. Kantian, H. P. B\"uchler, P. Zoller, K. Winkler, G.

Thalhammer, F. Lang, R. Grimm, J. Hecker Denschlag

Comments: 7 pages, 3 figures, Proceedings of ICAP-2006 (Innsbruck)

Subj-class: Other

\\ ( http://arXiv.org/abs/cond-mat/0608721 , 135kb)

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Paper: quant-ph/0609003

Date: Fri, 1 Sep 2006 08:09:33 GMT (870kb)

Title: Influence of classical resonances on chaotic tunnelling

Authors: Amaury Mouchet (LMPT), Christopher Eltschka, Peter Schlagheck

Proxy: ccsd ccsd-00090587

Journal-ref: Physical Review E 74 (2006) 026211

DOI: 10.1103/PhysRevE.74.026211

\\

Dynamical tunnelling between symmetry-related stable modes is studied in the

periodically driven pendulum. We present strong evidence that the tunnelling

process is governed by nonlinear resonances that manifest within the regular

phase-space islands on which the stable modes are localized. By means of a

quantitative numerical study of the corresponding Floquet problem, we identify

the trace of such resonances not only in the level splittings between

near-degenerate quantum states, where they lead to prominent plateau

structures, but also in overlap matrix elements of the Floquet eigenstates,

which reveal characteristic sequences of avoided crossings in the Floquet

spectrum. The semiclassical theory of resonance-assisted tunnelling yields good

overall agreement with the quantum-tunnelling rates, and indicates that partial

barriers within the chaos might play a prominent role.

\\ ( http://arXiv.org/abs/quant-ph/0609003 , 870kb)

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Paper: cond-mat/0609036

Date: Sat, 2 Sep 2006 07:00:33 GMT (114kb)

Title: Screening effect and delocalization of interacting Bose-Einstein

condensates in random potentials

Authors: Laurent Sanchez-Palencia (LCFIO)

Proxy: ccsd ccsd-00090760

Subj-class: Other

\\

We theoretically investigate the physics of interacting Bose-Einstein

condensates at equilibrium in a weak (possibly random) potential. We develop a

perturbation approach to derive the condensate wavefunction for an amplitude of

the potential smaller than the chemical potential of the condensate and for an

arbitrary spatial variation scale of the potential. Applying this theory to

disordered potentials, we find in particular that, if the healing length is

smaller than the latter, the condensate assumes a delocalized Thomas-Fermi

profile. In the opposite situation where the typical variation scale of the

potential is smaller than the healing length, we show that the random potential

can be significantly screened and, in the meanfield regime, the condensate

wavefunction can remain delocalized, even for very small correlation lengths of

the disorder.

\\ ( http://arXiv.org/abs/cond-mat/0609036 , 114kb)

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Paper: cond-mat/0609047

Date: Sun, 3 Sep 2006 11:59:52 GMT (74kb)

Title: Intrinsic dephasing in one dimensional ultracold atom interferometers

Authors: Rafi Bistritzer and Ehud Altman (Weizmann)

Subj-class: Other; Mesoscopic Systems and Quantum Hall Effect

\\

Quantum phase fluctuations play a crucial role in low dimensional systems. In

particular they prevent true long range phase order from forming in one

dimensional condensates, even at zero temperature. Nevertheless, by dynamically

splitting the condensate into two parallel decoupled tubes, a macroscopic

relative phase, can be imposed on the system. This kind of setup can serve as a

matter wave interferometer, which relies on the interference between the

displaced condensates as a measure of the relative phase between them. Here we

show how the quantum phase fluctuations, which are so effective in equilibrium,

act to destroy the macroscopic relative phase that was imposed as a non

equilibrium initial condition of the interferometer. We show that the phase

coherence between the two condensates decays exponentially with a dephasing

time that depends on intrinsic parameters: the dimensionless interaction

strength, sound velocity and density. Interestingly, at low temperatures the

dephasing time is almost independent of temperature. At temperatures higher

than a crossover scale T* dephasing gains significant temperature dependance.

In contrast to the usual phase diffusion, which is essentially an effect of

confinement, the dephasing due to fluctuations in one dimension is a bulk

effect that survives the thermodynamic limit.

\\ ( http://arXiv.org/abs/cond-mat/0609047 , 74kb)

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Paper: cond-mat/0609052

Date: Mon, 4 Sep 2006 07:28:03 GMT (21kb)

Title: Quantum Field Theoretical Description of Unstable Behavior of

Bose-Einstein Condensates in a Trapping Potential with Complex Eigenvalues of

Bogoliubov-de Gennes Equations

Authors: M. Mine, M. Okumura, T. Sunaga, Y. Yamanaka

Comments: 30 pages

Subj-class: Other

\\

The Bogoliubov-de Gennes equations are used for a number of theoretical works

on the trapped Bose-Einstein condensates. These equations are known to give the

energies of the quasi-particles when all the eigenvalues are real. We consider

the case in which these equations have complex eigenvalues. We give the

complete set including those modes whose eigenvalues are complex. The quantum

fields which represent neutral atoms are expanded in terms of the complete set.

It is shown that the state space is an indefinite metric one and that the free

Hamiltonian is not diagonalizable in the conventional bosonic representation.

We introduce a criterion to select quantum states describing the metastablity

of the condensate, called the physical state conditions. In order to study the

instability, we formulate the linear response of the density against the

time-dependent external perturbation within the regime of Kubo's linear

response theory. Some states, satisfying all the physical state conditions,

give the blow-up and damping behavior of the density distributions

corresponding to the complex eigenmodes. It is consistent with the result of

the recent analyses using the time-dependent Gross-Pitaevskii equation.

\\ ( http://arXiv.org/abs/cond-mat/0609052 , 21kb)

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Paper: cond-mat/0609061

Date: Mon, 4 Sep 2006 10:21:26 GMT (467kb)

Title: Einstein-de Haas effect for a $^{87}$Rb atoms condensate

Authors: Krzysztof Gawryluk, Miros{\l}aw Brewczyk, Kai Bongs, and Mariusz Gajda

Comments: 4 pages, 5 figures

Subj-class: Other

\\

We consider a condensate of $^{87}$Rb atoms in an F=1 hyperfine state

confined in an optical dipole trap. Assuming the magnetic moments of all atoms

are initially aligned along the magnetic field we observe, after the field's

direction is reversed, a transfer of atoms to other Zeeman states due to the

dipolar interaction. We find that there exist resonances which amplify the

effect of dipolar interaction. When the resonance condition is satisfied the

transfer of atoms to $m_F=0,-1$ states might be of the order of the initial

population of $m_F=1$ component. While changing the magnetic moments during the

transfer, the atomsacquire an orbital angular momentum and start to circulate

around the center of the trap. This is a realization of the famous Einstein-de

Haas effect in systems of cold gases. Due to the dipolar resonances, it becomes

possible to observe this phenomenon even in a condensate of $^{87}$Rb (F=1)

atoms that have very small magnetic moment.

\\ ( http://arXiv.org/abs/cond-mat/0609061 , 467kb)

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Paper: cond-mat/0609063

Date: Mon, 4 Sep 2006 12:56:09 GMT (238kb)

Title: Stochastic mean-field approach to strongly correlated phases of

ultracold fermions

Authors: Olivier Juillet (LPCC)

Comments: Submitted to Physical Review Letters

Proxy: ccsd ccsd-00090944

Subj-class: Other

\\

We propose a new projector quantum Monte-Carlo method to investigate the

ground state of ultracold fermionic atoms modeled by a lattice Hamiltonian with

an on-site interaction. The many-body state is reconstructed from Slater

determinants that evolve in imaginary-time according to a stochastic mean-field

motion without explicit sign problems. The method is applied to calculate

ground-state energies and correlation functions of the repulsive

two-dimensional Hubbard model. Numerical results for the unitary Fermi gas

validate simulations with nodal constraints.

\\ ( http://arXiv.org/abs/cond-mat/0609063 , 238kb)

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Paper: cond-mat/0609067

Date: Mon, 4 Sep 2006 14:29:55 GMT (21kb)

Title: Mean-Field vs Monte-Carlo equation of state for the expansion of a Fermi

superfluid in the BCS-BEC crossover

Authors: Luca Salasnich (CNISM and CNR-INFM, Padova) and Nicola Manini (Univ.

Milano)

Comments: 13 pages, 3 figures, presented to the 15th International Laser

Physics Workshop (Lausanne, July 24-28, 2006); to be published in Laser

Physics

Subj-class: Other

\\

The equation of state (EOS) of a Fermi superfluid is investigated in the

BCS-BEC crossover at zero temperature. We discuss the EOS based on Monte-Carlo

(MC) data and asymptotic expansions and the EOS derived from the extended BCS

(EBCS) mean-field theory. Then we introduce a time-dependent density

functional, based on the bulk EOS and Landau's superfluid hydrodynamics with a

von Weizs\"acker-type correction, to study the free expansion of the Fermi

superfluid. We calculate the aspect ratio and the released energy of the

expanding Fermi cloud showing that MC EOS and EBCS EOS are both compatible with

the available experimental data of $^6$Li atoms. We find that the released

energy satisfies an approximate analytical formula that is quite accurate in

the BEC regime. For an anisotropic droplet, our numerical simulations show an

initially faster reversal of anisotropy in the BCS regime, later suppressed by

the BEC fluid.

\\ ( http://arXiv.org/abs/cond-mat/0609067 , 21kb)

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Paper: physics/0605225

replaced with revised version Sat, 2 Sep 2006 07:52:34 GMT (70kb)

Title: Worm Algorithm and Diagrammatic Monte Carlo: A New Approach to

Continuous-Space Path Integral Monte Carlo Simulations

Authors: M. Boninsegni, N. V. Prokof'ev and B. V. Svistunov

Comments: 17 pages, 13 figures

Subj-class: Computational Physics; Statistical Mechanics

Journal-ref: Phys. Rev. E 74, 036701 (2006)

\\ ( http://arXiv.org/abs/physics/0605225 , 70kb)

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Paper: quant-ph/0609009

Date: Sat, 2 Sep 2006 01:59:50 GMT (182kb)

Title: Extended Coherence Time with Atom-Number Squeezed Sources

Authors: Wei Li, Ari K. Tuchman, Hui-Chun Chien, Mark A. Kasevich

Comments: 4 pages, 4 figures

\\

Coherence properties of Bose-Einstein condensates offer the potential for

improved interferometric phase contrast. However, decoherence effects due to

the mean-field interaction shorten the coherence time, thus limiting potential

sensitivity. In this work, we demonstrate increased coherence times with number

squeezed states in an optical lattice using the decay of Bloch oscillations to

probe the coherence time. We extend coherence times by a factor of 2 over those

expected with coherent state BEC interferometry. We observe quantitative

agreement with theory both for the degree of initial number squeezing as well

as for prolonged coherence times.

\\ ( http://arXiv.org/abs/quant-ph/0609009 , 182kb)

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Paper: quant-ph/0609019

Date: Mon, 4 Sep 2006 14:25:04 GMT (481kb)

Title: Producing and Detecting Correlated atoms

Authors: Christoph I. Westbrook (LCFIO), Martijn Schellekens (LCFIO),

Aur\'{e}lien Perrin (LCFIO), Valentina Krachmalnicoff (LCFIO), Jose Carlos

Viana Gomes (LCFIO, Departamento De Fisica, Universidade Do Minho),

Jean-Baptiste Trebbia (LCFIO), J\'{e}r\^{o}me Est\`{e}ve (LCFIO), Hong Chang

(LCFIO), Isabelle Bouchoule (LCFIO), Denis Boiron (LCFIO), Alain Aspect

(LCFIO), Tom Jeltes (LASER Center Vrije Universiteit Amsterdam), John

McNamara (LASER Center Vrije Universiteit Amsterdam), Wim Hogervorst (LASER

Center Vrije Universiteit Amsterdam), Wim Vassen (LASER Center Vrije

Universiteit Amsterdam)

Comments: to appear in conference proceedings "Atomic Physics 20"

Proxy: ccsd ccsd-00090936

Journal-ref: International Conference on Atomic Physics,, Autriche (2006)

\\

We discuss experiments to produce and detect atom correlations in a

degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic

analog of the celebrated Hanbury Brown Twiss experiment, in which atom

correlations result simply from interference effects without any atom

interactions.We have performed this experiment for both bosons and fermions.

Next we show how atom interactions produce correlated atoms using the atomic

analog of spontaneous four-wavemixing. Finally, we briefly mention experiments

on a one dimensional gas on an atom chip in which correlation effects due to

both interference and interactions have been observed.

\\ ( http://arXiv.org/abs/quant-ph/0609019 , 481kb)

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Paper: physics/0609013

Date: Fri, 1 Sep 2006 21:32:23 GMT (180kb)

Title: Simple Theoretical Models for Resonant Cold Atom Interactions

Authors: Paul S. Julienne, Bo Gao

Comments: To be published in the Proceedings of the 20th International

Conference on Atomic Physics, held in Innsbruck, Austria, July 2006

Subj-class: Atomic Physics

\\

Magnetically tunable scattering resonances have been used with great success

for precise control of s-wave scattering lengths in ultracold atomic

collisions. We describe relatively simple yet quite powerful analytic

treatments of such resonances based on the analytic properties of the van der

Waals long range potential. This theory can be used to characterize a number of

properties of specific resonances that have been used successfully in various

experiments with $^{87}$Rb, $^{85}$Rb, $^{40}$K, and $^{6}$Li. Optical Feshbach

resonances are also possible and may be practical with narrow intercombination

line photoassociative transitions in species like Sr and Yb.

\\ ( http://arXiv.org/abs/physics/0609013 , 180kb)

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Paper: physics/0609028

Date: Mon, 4 Sep 2006 07:33:31 GMT (852kb)

Title: Large atom number Bose-Einstein condensate of sodium

Authors: K.M.R. van der Stam, E.D. van Ooijen, R. Meppelink, J.M. Vogels, and

P. van der Straten

Comments: 11 pages, 12 figures, submitted to Review Of Scientific Instruments

Subj-class: Atomic Physics

\\

We describe the setup to create a large Bose-Einstein condensate containing

more than 120x10^6 atoms. In the experiment a thermal beam is slowed by a

Zeeman slower and captured in a dark-spot magneto-optical trap (MOT). A typical

dark-spot MOT in our experiments contains 2.0x10^10 atoms with a temperature of

320 microK and a density of about 1.0x10^11 atoms/cm^3. The sample is spin

polarized in a high magnetic field, before the atoms are loaded in the magnetic

trap. Spin polarizing in a high magnetic field results in an increase in the

transfer efficiency by a factor of 2 compared to experiments without spin

polarizing. In the magnetic trap the cloud is cooled to degeneracy in 50 s by

evaporative cooling. To suppress the 3-body losses at the end of the

evaporation the magnetic trap is decompressed in the axial direction.

\\ ( http://arXiv.org/abs/physics/0609028 , 852kb)

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Paper: cond-mat/0508466

replaced with revised version Tue, 5 Sep 2006 13:30:31 GMT (130kb)

Title: Hanbury Brown Twiss effect for ultracold quantum gases

Authors: M. Schellekens, R. Hoppeler, A. Perrin, J. Viana Gomes, D. Boiron, A.

Aspect, C. I. Westbrook

Comments: Figure 1 available

Subj-class: Other

Journal-ref: published in Science 310, 648 (2005)

\\ ( http://arXiv.org/abs/cond-mat/0508466 , 130kb)

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Paper: cond-mat/0603626

replaced with revised version Tue, 5 Sep 2006 17:52:35 GMT (0kb,I)

Title: Non-Positive $\alpha$ Rule for Continuous Phase Transition Lines

Authors: Nikolay Prokof'ev, Boris Svistunov

Comments: This paper has been withdrawn by the authors, due to a possible flaw

in its logic. Namely, it has been taken for granted that the the structure of

regular part of Helmholtz free energy is insensitive to the sign of the

specific heat exponent

Subj-class: Statistical Mechanics

\\ ( http://arXiv.org/abs/cond-mat/0603626 , 0kb)

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Paper: cond-mat/0605039

replaced with revised version Tue, 5 Sep 2006 09:01:26 GMT (62kb)

Title: Intermediate temperature superfluidity in an atomic Fermi gas with

population imbalance

Authors: Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin

Comments: Replace with the published version

Subj-class: Strongly Correlated Electrons; Superconductivity

Journal-ref: Phys. Rev. Lett. 97, 090402 (2006)

DOI: 10.1103/PhysRevLett.97.090402

\\ ( http://arXiv.org/abs/cond-mat/0605039 , 62kb)

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Paper: cond-mat/0606743

replaced with revised version Tue, 5 Sep 2006 01:14:33 GMT (62kb)

Title: Predicted quantum stripe ordering in optical lattices

Authors: Congjun Wu, W. Vincent Liu, Joel Moore, and Sankar Das Sarma

Comments: 5 pages, three figures

Subj-class: Strongly Correlated Electrons; Superconductivity

\\ ( http://arXiv.org/abs/cond-mat/0606743 , 62kb)

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Paper: cond-mat/0609050

Date: Mon, 4 Sep 2006 02:04:11 GMT (574kb)

Title: Quantum phase transitions of light

Authors: Andrew D. Greentree, Charles Tahan, Jared H. Cole, and L. C. L.

Hollenberg

Comments: 11 pages, 5 figures (2 in colour)

Subj-class: Other

\\

Recently, condensed matter and atomic experiments have reached a length-scale

and temperature regime where new quantum collective phenomena emerge. Finding

such physics in systems of photons, however, is problematic, as photons

typically do not interact with each other and can be created or destroyed at

will. Here, we introduce a physical system of photons that exhibits strongly

correlated dynamics on a meso-scale. By adding photons to a two-dimensional

array of coupled optical cavities each containing a single two-level atom in

the photon-blockade regime, we form dressed states, or polaritons, that are

both long-lived and strongly interacting. Our zero temperature results predict

that this photonic system will undergo a characteristic Mott insulator

(excitations localised on each site) to superfluid (excitations delocalised

across the lattice) quantum phase transition. Each cavity's impressive photon

out-coupling potential may lead to actual devices based on these quantum

many-body effects, as well as observable, tunable quantum simulators. We

explicitly show that such phenomena may be observable in micro-machined diamond

containing nitrogen-vacancy colour centres and superconducting microwave

strip-line resonators.

\\ ( http://arXiv.org/abs/cond-mat/0609050 , 574kb)

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Paper: physics/0605092

replaced with revised version Tue, 5 Sep 2006 12:01:19 GMT (341kb)

Title: Diffuse reflection of a Bose-Einstein condensate from a rough evanescent

wave mirror

Authors: Helene Perrin, Yves Colombe, Brigitte Mercier, Vincent Lorent, and

Carsten Henkel

Comments: submitted to J Phys B, 10 pages, 6 figures

Subj-class: Atomic Physics; Optics

\\ ( http://arXiv.org/abs/physics/0605092 , 341kb)

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Paper (*cross-listing*): nucl-th/0608063

Date: Mon, 28 Aug 2006 11:10:21 GMT (96kb)

Date (revised v2): Wed, 6 Sep 2006 10:07:25 GMT (96kb)

Title: $D$-dimensions Dirac fermions BEC-BCS cross-over thermodynamics with

Lorentz violation

Authors: Ji-sheng Chen

Comments: 7 pages, 2 figures; typos fixed

Subj-class: Nuclear Theory; Statistical Mechanics

\\

An analytical attempt is made with an effective Proca Lagrangian action to

address the vector condensation Lorentz violation effects on the equation of

state of strongly interacting fermions system. The in-medium many-body

renormalization effect is introduced as an external field approximation through

a fictive generalized Thomson Problem background. The expressions for the

$d$-dimensions thermodynamics are given with finite $S$-wave scattering length.

In the non-relativistic limit for $d=3$, universal coefficient $\xi ={4/9}$ and

energy gap $\Delta ={5/18}\epsilon_f $ are reasonably consistent with the

existed theoretical and experimental results. In the unitary limit for $d=2$

and T=0, the universal dimensionless coefficient can even approach the extreme

occasion $\xi=0$ corresponding to $m^*=\infty$ which can be mapped to the

strongly coupled two-dimensions electrons and is quite similar to the

3-dimensions Bose-Einstein Condensation of ideal boson gas. Instead, for $d=1$,

the universal coefficient $\xi$ is negative, implying the non-existence of

phase transition from superfluidity to normal state. The solutions manifest the

quantum Ising characteristic of the strongly coupled unitary fermions gas.

\\ ( http://arXiv.org/abs/nucl-th/0608063 , 96kb)

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Paper: cond-mat/0605169

replaced with revised version Wed, 6 Sep 2006 07:15:35 GMT (211kb)

Title: Fermion pairing with spin-density imbalance in an optical lattice

Authors: T. Koponen, J. Kinnunen, J.-P. Martikainen, L.M. Jensen, and P. Torma

Comments: 18 pages, 17 figures, replaced with published version, also available

at http://stacks.iop.org/1367-2630/8/179

Subj-class: Superconductivity; Materials Science

Journal-ref: New J. Phys. 8 (2006) 179

DOI: 10.1088/1367-2630/8/9/179

\\ ( http://arXiv.org/abs/cond-mat/0605169 , 211kb)

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Paper: cond-mat/0605148

replaced with revised version Tue, 5 Sep 2006 21:55:43 GMT (9kb)

Title: Bose-Einstein condensation and entanglement in magnetic systems

Authors: Mucio A. Continentino

Comments: 7 pages, 1 Table; accepted version; changes in text and new

references

Subj-class: Strongly Correlated Electrons; Statistical Mechanics

Journal-ref: J.Phys.: Condens. Matter 18 (2006) 8395-8401

\\ ( http://arXiv.org/abs/cond-mat/0605148 , 9kb)

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Paper: cond-mat/0608611

replaced with revised version Wed, 6 Sep 2006 19:13:48 GMT (47kb)

Title: Excited state spectra at the superfluid-insulator transition out of

paired condensates

Authors: Stephen Powell and Subir Sachdev

Comments: 4 pages, 1 figure

Subj-class: Strongly Correlated Electrons; Superconductivity

\\ ( http://arXiv.org/abs/cond-mat/0608611 , 47kb)

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Paper: physics/0609041

Date: Wed, 6 Sep 2006 00:20:28 GMT (53kb)

Title: Robust, High-speed, All-Optical Atomic Magnetometer

Authors: J. M. Higbie, E. Corsini, and D. Budker

Comments: 8 pages, 5 figs

Subj-class: Atomic Physics; Instrumentation and Detectors

\\

A self-oscillating magnetometer based on the nonlinear magneto-optical

rotation effect with separate modulated pump and unmodulated probe beams is

demonstrated. This device possesses a bandwidth exceeding $1\khz$. Pump and

probe are delivered by optical fiber, facilitating miniaturization and

modularization. The magnetometer has been operated both with vertical-cavity

surface-emitting lasers (VCSELs), which are well suited to portable

applications, and with conventional edge-emitting diode lasers. A sensitivity

of around $3 {\rm nG}$ is achieved for a measurement time of $1\s$.

\\ ( http://arXiv.org/abs/physics/0609041 , 53kb)

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Paper: physics/0608088

replaced with revised version Wed, 6 Sep 2006 14:27:22 GMT (361kb)

Title: Evaporative cooling in a radio-frequency trap

Authors: Carlos L. Garrido Alzar (1), H\'el\`ene Perrin (1), Barry M. Garraway

(2), Vincent Lorent (1) ((1) Laboratoire de Physique des Lasers,

CNRS-Universit\'e Paris 13, Villetaneuse, France, (2) Department of Physics

and Astronomy, University of Sussex, Brighton, United Kingdom)

Comments: 12 pages, 11 figures

Subj-class: Atomic Physics

\\ ( http://arXiv.org/abs/physics/0608088 , 529kb)

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Paper: cond-mat/0609156

Date: Thu, 7 Sep 2006 06:35:29 GMT (8kb)

Title: Local stability conditions for asymmetric Fermi superfluid

Authors: S.-K. Yip

Subj-class: Superconductivity

\\

Two different local stability conditions for an asymmetric superfluid has

been discussed in the literature. We here consider the relations between them.

\\ ( http://arXiv.org/abs/cond-mat/0609156 , 8kb)

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Paper: cond-mat/0609159

Date: Thu, 7 Sep 2006 08:09:07 GMT (30kb)

Title: Condensation of phonons in an ultracold Bose gas

Authors: Yu. Kagan and L.A. Manakova

Comments: 5 pages, 1 figure, submitted to Phys.Rev.Letters

Subj-class: Other

\\

We consider the generation of longitudinal phonons in an elongated

Bose-condensed gas at zero temperature due to parametric resonance as a result

of the modulation of the transverse trap frequency. The nonlinear temporal

evolution with account of the phonon-phonon interaction leads self-consistently

to the formation of the stationary state with the macroscopic occupation of a

single phonon quantum state.

\\ ( http://arXiv.org/abs/cond-mat/0609159 , 30kb)

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\\

Paper: cond-mat/0609167

Date: Thu, 7 Sep 2006 10:50:05 GMT (38kb)

Title: Thermodynamics of Solitonic Matter Waves in a Toroidal Trap

Authors: L. Salasnich (CNISM and CNR-INFM), A. Parola (Univ. Insubria), and L.

Reatto (Univ. Milano)

Comments: 4 pages, 4 figures, to be published in Physical Review A as a Rapid

Communication. Related papers can be found at

http://www.padova.infm.it/salasnich/tdqg.html

Subj-class: Other; Statistical Mechanics

\\

We investigate the thermodynamic properties of a Bose-Einstein condensate

with negative scattering length confined in a toroidal trapping potential. By

numerically solving the coupled Gross-Pitaevskii and Bogoliubov-de Gennes

equations, we study the phase transition from the uniform state to the

symmetry-breaking state characterized by a bright-soliton condensate and a

localized thermal cloud. In the localized regime three states with a finite

condensate fraction are present: the thermodynamically stable localized state,

a metastable localized state and also a metastable uniform state. Remarkably,

the presence of the stable localized state strongly increases the critical

temperature of Bose-Einstein condensation.

\\ ( http://arXiv.org/abs/cond-mat/0609167 , 38kb)

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\\

Paper: cond-mat/0609169

Date: Thu, 7 Sep 2006 11:25:58 GMT (123kb)

Title: The new physics of non-equilibrium condensates: insights from classical

dynamics

Authors: P. R. Eastham

Comments: 10 pages, 4 figures, submitted for a special issue of J. Phys.:

Condensed Matter on "Optical coherence and collective phenomena in

nanostructures"

Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall

Effect

\\

We discuss the dynamics of classical Dicke-type models, aiming to clarify the

mechanisms by which coherent states could develop in potentially

non-equilibrium systems such as semiconductor microcavities. We present

simulations of an undamped model which show spontaneous coherent states with

persistent oscillations in the magnitude of the order parameter. These states

are generalisations of superradiant ringing to the case of inhomogeneous

broadening. They resemble the persistent gap oscillations proposed in fermionic

atomic condensates, but arise from different initial conditions. We show that

introducing randomness into the couplings can suppress the oscillations,

leading to a limiting dynamics with a time-independent order parameter. This

demonstrates that non-equilibrium generalisations of polariton condensates can

be created even without dissipation. We explain the dynamical origins of the

coherence as instabilities of the normal state, and consider how it can

additionally develop through scattering and dissipation.

\\ ( http://arXiv.org/abs/cond-mat/0609169 , 123kb)

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\\

Paper: cond-mat/0609171

Date: Thu, 7 Sep 2006 13:16:56 GMT (413kb)

Title: Symmetry Breaking in Bose-Einstein Condensates

Authors: Masahito Ueda, Yuki Kawaguchi, Hiroki Saito, Rina Kanamoto, and

Tatsuya Nakajima

Comments: Submitted to the proceedings of International Conference on Atomic

Physics 2006

Subj-class: Other

\\

A gaseous Bose-Einstein condensate (BEC) offers an ideal testing ground for

studying symmetry breaking, because a trapped BEC system is in a mesoscopic

regime, and situations exist under which symmetry breaking may or may not

occur. Investigating this problem can explain why mean-field theories have been

so successful in elucidating gaseous BEC systems and when many-body effects

play a significant role. We substantiate these ideas in four distinct

situations: namely, soliton formation in attractive BECs, vortex nucleation in

rotating BECs, spontaneous magnetization in spinor BECs, and spin texture

formation in dipolar BECs.

\\ ( http://arXiv.org/abs/cond-mat/0609171 , 413kb)

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\\

Paper: cond-mat/0609172

Date: Thu, 7 Sep 2006 14:22:48 GMT (356kb)

Title: Reaching the hydrodynamic regime in a Bose-Einstein condensate by

suppression of avalanche

Authors: K.M.R. van der Stam, R. Meppelink, J.M. Vogels, and P. van der Straten

Comments: Article submitted for Phys. Rev. Letters, 6 figures

Subj-class: Other

\\

We report the realization of a Bose-Einstein condensate (BEC) in the

hydrodynamic regime. The hydrodynamic regime is reached by evaporative cooling

at a relative low density suppressing the effect of avalanches. With the

suppression of avalanches a BEC containing 120.10^6 atoms is produced. The

collisional opacity can be tuned from the collisionless regime to a collisional

opacity of more than 3 by compressing the trap after condensation. In the

collisional opaque regime a significant heating of the cloud at time scales

shorter than half of the radial trap period is measured. This is direct proof

that the BEC is hydrodynamic.

\\ ( http://arXiv.org/abs/cond-mat/0609172 , 356kb)

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\\

Paper: cond-mat/0606322

replaced with revised version Thu, 7 Sep 2006 02:50:47 GMT (749kb)

Title: Finite Temperature Phase Diagram of a Two-Component Fermi Gas with

Density Imbalance

Authors: Lianyi He, Meng Jin and Pengfei Zhuang

Comments: 12 pages, 10 figures, references added

Subj-class: Superconductivity; Other; Statistical Mechanics; Atomic Physics

\\ ( http://arXiv.org/abs/cond-mat/0606322 , 749kb)

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\\

Paper: cond-mat/0606398

replaced with revised version Thu, 7 Sep 2006 09:08:52 GMT (985kb)

Title: Landau damping: instability mechanism of superfluid Bose gases moving in

optical lattices

Authors: Kiyohito Iigaya, Satoru Konabe, Ippei Danshita, and Tetsuro Nikuni

Comments: 9 pages, 5 figures

Subj-class: Other

\\ ( http://arXiv.org/abs/cond-mat/0606398 , 985kb)

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\\

Paper: quant-ph/0609054

Date: Thu, 7 Sep 2006 00:05:56 GMT (160kb)

Title: How to Measure the Quantum State of Collective Atomic Spin Excitation

Authors: Koji Usami, Jun-ichi Takahashi, and Mikio Kozuma

Comments: 6 pages, to appear in Phys. Rev. A

\\

The spin state of an atomic ensemble can be viewed as two bosonic modes,

i.e., a quantum signal mode and a $c$-numbered ``local oscillator'' mode when

large numbers of spin-1/2 atoms are spin-polarized along a certain axis and

collectively manipulated within the vicinity of the axis. We present a concrete

procedure which determines the spin-excitation-number distribution, i.e., the

diagonal elements of the density matrix in the Dicke basis for the collective

spin state. By seeing the collective spin state as a statistical mixture of the

inherently-entangled Dicke states, the physical picture of its multi-particle

entanglement is made clear.

\\ ( http://arXiv.org/abs/quant-ph/0609054 , 160kb)

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\\

Paper: physics/0603108

replaced with revised version Thu, 7 Sep 2006 16:05:09 GMT (247kb)

Title: Optimizing the Stark-decelerator beamline for the trapping of cold

molecules using evolutionary strategies

Authors: Joop J. Gilijamse, Jochen K\"upper, Steven Hoekstra, Nicolas

Vanhaecke, Sebastiaan Y. T. van de Meerakker, Gerard Meijer

Comments: 7 pages, 4 figures (RevTeX) (v2) minor corrections (v3) no changes to

manuscript, but fix author list in arXiv abstract

Subj-class: Instrumentation and Detectors; Accelerator Physics; Atomic Physics

Journal-ref: Phys. Rev. A 73, 063410 (2006)

DOI: 10.1103/PhysRevA.73.063410

\\ ( http://arXiv.org/abs/physics/0603108 , 247kb)

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\\

Paper: cond-mat/0609187

Date: Fri, 8 Sep 2006 02:26:15 GMT (23kb)

Title: Pairing fluctuations and the superfluid density through the BCS-BEC

crossover

Authors: E. Taylor, A. Griffin, N. Fukushima, Y. Ohashi

Comments: 30 pages

Subj-class: Other

\\

We derive an expression for the superfluid density of a uniform two-component

Fermi gas through the BCS-BEC crossover in terms of the thermodynamic potential

in the presence of an imposed superfluid flow. Treating the pairing

fluctuations in a Gaussian approximation following the approach of Nozi\`eres

and Schmitt-Rink, we use this definition of $\rho_s$ to obtain an explicit

result which is valid at finite temperatures and over the full BCS-BEC

crossover. It is crucial that the BCS gap $\Delta$, the chemical potential

$\mu$, and $\rho_s$ all include the effect of fluctuations at the same level in

a self-consistent manner. We show that the normal fluid density $\rho_n \equiv

n - \rho_s$ naturally separates into a sum of contributions from Fermi BCS

quasiparticles ($\rho^F_{n}$) and Bose collective modes ($\rho^B_{n}$). The

expression for $\rho^F_{n}$ is just Landau's formula for a BCS Fermi superfluid

but now calculated over the BCS-BEC crossover. The expression for the Bose

contribution $\rho^B_{n}$ is more complicated and only reduces to Landau's

formula for a Bose superfluid in the extreme BEC limit, where all the fermions

have formed stable Bose pairs and the Bogoliubov excitations of the associated

molecular Bose condensate are undamped. In a companion paper, we present

numerical calculations of $\rho_s$ using an expression equivalent to the one

derived in this paper, over the BCS-BEC crossover, including unitarity, and at

finite temperatures.

\\ ( http://arXiv.org/abs/cond-mat/0609187 , 23kb)

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\\

Paper: cond-mat/0609195

Date: Fri, 8 Sep 2006 10:45:52 GMT (996kb)

Title: Dirty Bosons in Disordered Optical Potentials

Authors: Pearl J.Y. Louis and Makoto Tsubota

Comments: 4 pages, 4 figures (low res)

Subj-class: Disordered Systems and Neural Networks

\\

In this work we systematically investigate the condensate properties,

superfluid properties and quantum phase transitions in interacting Bose gases

trapped in disordered optical potentials. We solve the Bose-Hubbard Hamiltonian

exactly for these `dirty' Bose gases for different: (a) types of disorder, (b)

disorder strengths, and (c) interatomic interactions. The three types of

disorder we study are: quasiperiodic disorder, uniform random disorder and

random speckle-type disorder. We find that the Bose glass phase, as identified

by Fisher \textit{et al.} [Phys. Rev. B {\bf 40}, 546 (1989)], contains a

normal condensate component and we show how the three different factors listed

above affect it.

\\ ( http://arXiv.org/abs/cond-mat/0609195 , 996kb)

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\\

Paper (*cross-listing*): physics/9802052

Date: Fri, 27 Feb 1998 15:17:57 GMT (17kb)

Title: Medium modification of two-particle scattering in nonideal Bose systems

Authors: H. Stein, K. Morawetz, and G. R\"opke

Categories: physics.atom-ph physics.acc-ph

Subj-class: Atomic Physics; Accelerator Physics; Statistical Mechanics

Journal-ref: Phys.Rev. A55 (2000) 1945

\\

Medium modification of scattering properties in interacting Bose systems are

considered by solving the Bethe-Salpeter equation. An equation of state for the

normal phase (generalized Beth-Uhlenbeck formula) is given using the in-medium

phase shifts to include two-particle correlations. Conclusions are drawn for

systems of bosonic atoms with repulsive interaction such as sodium $^{23}$Na

and rubidium $^{87}$Rb. It is shown that the in-medium scattering length and

the absolute value of the in-medium scattering phase shift for low scattering

energies increase with density.

\\ ( http://arXiv.org/abs/physics/9802052 , 17kb)

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\\

Paper: cond-mat/0304358

replaced with revised version Fri, 8 Sep 2006 15:30:58 GMT (207kb)

Title: Non-Gaussian Velocity Distributions in Optical Lattices

Authors: Johan Jersblad (Department of Physics, Department of Physics), Harald

Ellmann (Department of Physics), Kristian St\"{o}chkel (Department of

Physics), Anders Kastberg (Department of Physics), Laurent Sanchez-Palencia

(LKB - Lhomond), Robin Kaiser (LOD)

Comments: Final published version with 12 pages and 12 figures

Proxy: ccsd ccsd-00000311

Subj-class: Other

Journal-ref: Physical Review A 69 (2004) 013410

DOI: 10.1103/PhysRevA.69.013410

\\ ( http://arXiv.org/abs/cond-mat/0304358 , 207kb)

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\\

Paper: quant-ph/0608247

replaced with revised version Fri, 8 Sep 2006 00:33:27 GMT (355kb)

Title: Quantum many-body simulations using Gaussian phase-space representations

Authors: P. D. Drummond, P. Deuar, J. F. Corney

Comments: Short Review (10 pages); Corrected typo in eq (14); Added a few more

references

\\ ( http://arXiv.org/abs/quant-ph/0608247 , 355kb)

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\\

Paper: physics/0609073

Date: Fri, 8 Sep 2006 15:44:02 GMT (246kb)

Title: Dark Optical Lattice of Ring Traps for Cold Atoms

Authors: Emmanuel Courtade (PhLAM), Olivier Houde (PhLAM), Jean-Fran\c{c}ois

Cl\'{e}ment (PhLAM), Philippe Verkerk (PhLAM), Daniel Hennequin (PhLAM)

Comments: 4 pages, submitted to PRA

Proxy: ccsd ccsd-00092344

Subj-class: Atomic Physics

\\

We propose a new geometry of optical lattice for cold atoms, namely a lattice

made of a 1D stack of dark ring traps. It is obtained through the interference

pattern of a standard Gaussian beam with a counter-propagating hollow beam

obtained using a setup with two conical lenses. The traps of the resulting

lattice are characterized by a high confinement and a filling rate much larger

than unity, even if loaded with cold atoms from a MOT. We have implemented this

system experimentally, and obtained a lattice of ring traps populated with

typically 40 atoms per site with a life time of 30 ms. Applications in

statistical physics, quantum computing and Bose-Einstein condensate dynamics

are conceivable.

\\ ( http://arXiv.org/abs/physics/0609073 , 246kb)

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Till next week,

Matt.

-- ========================================================================= Dr M. J. Davis, Senior Lecturer in Physics School of Physical Sciences, email: mdavis_at_physics.uq.edu.au University of Queensland, ph : +61 7 334 69824 Brisbane, QLD 4072, fax : +61 7 336 51242 Australia. http://www.physics.uq.edu.au/people/mdavis/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland =========================================================================Received on Tue Sep 12 2006 - 13:35:41 EST

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