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

Date: Mon, 24 Apr 2006 13:21:59 +1000 (EST)

Date: Mon, 24 Apr 2006 13:21:59 +1000 (EST)

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

The home page for this mailing list is:

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

If you are interested in a 3 year postdoctoral fellow position in sunny Brisbane

you don't have much time left: http://www.physics.uq.edu.au/atomoptics/

On with the abstracts for this week:

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Paper: cond-mat/0604416

Date: Tue, 18 Apr 2006 14:32:08 GMT (157kb)

Title: Crossover States of Vortex Matter in Trapped Bose Condensates

Authors: S. Kragset, E. Babaev and A. Sudbo

Comments: 5 pages, 4 figures

Subj-class: Statistical Mechanics

\\

We perform Monte Carlo studies of vortices in three dimensions in a

cylindrical confinement, with uniform and nonuniform density. The former is

relevant to rotating 4He, the latter is relevant to a rotating trapped Bose

condensate. In the former case we find dominant angular thermal vortex

fluctuations close to the cylinder wall. For the latter case, a novel effect is

that at low temperatures the vortex solid close to the center of the trap

crosses directly over to a tension-less vortex tangle near the edge of the

trap. At higher temperatures an intermediate tension-full vortex liquid located

between the vortex solid and the vortex tangle, may exist.

\\ ( http://arXiv.org/abs/cond-mat/0604416 , 157kb)

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Paper: cond-mat/0604423

Date: Tue, 18 Apr 2006 19:02:08 GMT (48kb)

Title: Breakdown of the Local Density Approximation in Interacting Systems of

Cold Fermions in Strongly Anisotropic Traps

Authors: Adilet Imambekov, C. J. Bolech, Mikhail Lukin, and Eugene Demler

Comments: 4+e pages, 3 figures

Subj-class: Strongly Correlated Electrons

\\

We consider spin polarized mixtures of cold fermionic atoms on the BEC side

of the Feshbach resonance. We demonstrate that a strongly anisotropic confining

potential can give rise to a double peak structure in the axial distribution of

the density difference and a polarization dependent aspect ratio of the

minority species. We point out that both phenomena are not necessarily related

to phase separation and may appear as a result of the breakdown of the local

density approximation. We speculate on the implications of our findings for the

unitary regime.

\\ ( http://arXiv.org/abs/cond-mat/0604423 , 48kb)

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Paper: cond-mat/0604424

Date: Tue, 18 Apr 2006 19:06:23 GMT (131kb)

Title: Non-BCS superfluidity in trapped ultracold Fermi gases

Authors: L. M. Jensen, J. Kinnunen, and P. Torma

Comments: 4 pages, 4 figures

Subj-class: Strongly Correlated Electrons; Other

\\

Superconductivity and superfluidity of Fermions require, within the BCS

theory, matching of the Fermi energies of the two interacting Fermion species.

Difference in the number densities of the two species leads either to a normal

state, to phase separation, or - potentially - to exotic forms of superfluidity

such as FFLO-state, Sarma state or breached pair state. Such superfluidity is

of interest e.g. in condensed matter, high-energy and nuclear physics, but firm

experimental evidence is lacking. With the recently realized superfluids of

alkali Fermi gases, the first studies of density-imbalanced gases have shown

that these systems offer unprecedented opportunities for investigating this

question. Here we show that, due to the gases being trapped and isolated from

the environment in terms of particle exchange, exotic forms of superfluidity

appear as a shell around the BCS-superfluid core of the gas and, for large

density imbalance, in the core as well.

\\ ( http://arXiv.org/abs/cond-mat/0604424 , 131kb)

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Paper: cond-mat/0601681

replaced with revised version Mon, 17 Apr 2006 22:22:49 GMT (226kb)

Title: Exact Study of the 1D Boson Hubbard Model with a Superlattice Potential

Authors: V.G. Rousseau, M. Rigol, F. H\'ebert, D.P. Arovas, G.G. Batrouni, R.T.

Scalettar

Comments: 12 pages, 22 figures

Subj-class: Other; Strongly Correlated Electrons

\\ ( http://arXiv.org/abs/cond-mat/0601681 , 226kb)

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Paper: quant-ph/0511162

replaced with revised version Tue, 18 Apr 2006 09:38:13 GMT (196kb)

Title: Quantum phase transitions without thermodynamic limits

Authors: Dorje C. Brody, Daniel W. Hook, and Lane P. Hughston

Comments: 4 Pages, further references added

Subj-class: Quantum Physics; Statistical Mechanics

\\ ( http://arXiv.org/abs/quant-ph/0511162 , 196kb)

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Paper: quant-ph/0604128

Date: Tue, 18 Apr 2006 08:46:55 GMT (46kb)

Title: Generating superposition and entanglement of squeezed vacuum states

Authors: Zhi-Ming Zhang

Comments: 5 pages, 3 figures

\\

We propose a scheme for generating the superposition and the entanglement of

squeezed vacuum states of electromagnetical fields. The scheme involves

single-photon source, single photon detector, and cross Kerr nonlinearity. The

Kerr nonlinearity required for generating the superposition of squeezed vacuum

states is 1/2 of that required for generating the superposition of coherent

states. The proposal can also be extended to generate the entanglement states

between two coherent states and that between one coherent state and one

squeezed vacuum state.

\\ ( http://arXiv.org/abs/quant-ph/0604128 , 46kb)

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Paper: quant-ph/0604134

Date: Tue, 18 Apr 2006 19:55:21 GMT (395kb)

Title: Experimental continuous-variable entanglement of phase-locked bright

optical beams

Authors: Jietai Jing, Sheng Feng, Russell Bloomer, Olivier Pfister

Comments: 4 pages, 5 figures, submitted for publication

\\

We observed continuous-variable entanglement between two bright beams emitted

above threshold by a phase-difference-locked ultrastable optical parametric

oscillator. The amplitude-difference squeezing is -3 dB and the phase-sum one

is -1.35 dB. The beams are classically phase-locked at a frequency difference

of 161.8273240(5) MHz, continuously tunable by the OPO crystal temperature.

Such unprecedented frequency-difference stability paves the way for

implementing quantum frequency multiplexing and CV quantum information in the

frequency domain.

\\ ( http://arXiv.org/abs/quant-ph/0604134 , 385kb)

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Paper: physics/0604139

Date: Tue, 18 Apr 2006 14:55:36 GMT (116kb)

Title: Efficient formation of strongly bound ultracold cesium molecules by

photoassociation with tunneling

Authors: Mihaela Vatasescu, Claude M. Dion, and Olivier Dulieu

Comments: 15 pages with 7 figures. Submitted to J. Phys. B

Subj-class: Atomic Physics; Chemical Physics

\\

We calculate the rates of formation and detection of ultracold Cs_2 molecules

obtained from the photoassociation of ultracold atoms through the double-well

0g- (6S1/2 + 6P3/2) state. We concentrate on two features previously observed

experimentally and attributed to tunneling between the two wells [Vatasescu et

al 2000 Phys. Rev. A 61 044701]. We show that the molecules obtained are in

strongly bound levels (v''=5,6) of the metastable a 3Sigma_u+ (6S1/2 + 6S1/2)

ground electronic state.

\\ ( http://arXiv.org/abs/physics/0604139 , 116kb)

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Paper: physics/0604140

Date: Tue, 18 Apr 2006 15:55:37 GMT (288kb)

Title: Theoretical model for ultracold molecule formation via adaptive feedback

control

Authors: Ulrich Poschinger, Wenzel Salzmann, Roland Wester, Matthias

Weidemueller, Christiane P. Koch, Ronnie Kosloff

Subj-class: Atomic Physics

\\

We investigate pump-dump photoassociation of ultracold molecules with

amplitude- and phase-modulated femtosecond laser pulses. For this purpose a

perturbative model for the light-matter interaction is developed and combined

with a genetic algorithm for adaptive feedback control of the laser pulse

shapes. The model is applied to the formation of 85Rb2 molecules in a

magneto-optical trap. We find for optimized pulse shapes an improvement for the

formation of ground state molecules by more than a factor of 10 compared to

unshaped pulses at the same pump-dump delay time, and by 40% compared to

unshaped pulses at the respective optimal pump-dump delay time. Since our model

yields directly the spectral amplitudes and phases of the optimized pulses, the

results are directly applicable in pulse shaping experiments.

\\ ( http://arXiv.org/abs/physics/0604140 , 288kb)

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Paper: physics/0604130

Date: Tue, 18 Apr 2006 00:33:14 GMT (28kb)

Title: Finding Scientific Gems with Google

Authors: P. Chen, H. Xie, S. Maslov, and S. Redner

Comments: 6 pages, 4 figures, 2 tables, 2-column revtex4 format

Subj-class: Data Analysis, Statistics and Probability; Physics and Society

\\

We apply the Google PageRank algorithm to assess the relative importance of

all publications in the Physical Review family of journals from 1893--2003.

While the Google number and the number of citations for each publication are

positively correlated, outliers from this linear relation identify some

exceptional papers or "gems" that are universally familiar to physicists.

\\ ( http://arXiv.org/abs/physics/0604130 , 28kb)

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Paper: cond-mat/0604432

Date: Wed, 19 Apr 2006 03:26:11 GMT (35kb)

Title: Dipolar Bose gases: Many-body versus mean-field description

Authors: D.C.E. Bortolotti, S. Ronen, J.L. Bohn, D. Blume

Subj-class: Statistical Mechanics

\\

We characterize zero-temperature dipolar Bose gases under external spherical

confinement as a function of the dipole strength using the essentially exact

many-body diffusion Monte Carlo (DMC) technique. We show that the DMC energies

are reproduced accurately within a mean-field framework if the variation of the

s-wave scattering length with the dipole strength is accounted for properly.

Our calculations suggest stability diagrams and collapse mechanisms of dipolar

Bose gases that differ significantly from those previously proposed in the

literature.

\\ ( http://arXiv.org/abs/cond-mat/0604432 , 35kb)

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Paper: cond-mat/0604455

Date: Wed, 19 Apr 2006 17:52:07 GMT (216kb)

Title: The dynamics of condensate shells: collective modes and expansion

Authors: C. Lannert, T.-C. Wei, and S. Vishveshwara

Subj-class: Other

\\

We explore the physics of three-dimensional shell-shaped condensates,

relevant to cold atoms in "bubble traps" and to Mott insulator-superfluid

systems in optical lattices. We study the ground state of the condensate

wavefunction, spherically-symmetric collective modes, and expansion properties

of such a shell using a combination of analytical and numerical techniques. We

find two breathing-type modes with frequencies that are distinct from that of

the filled spherical condensate. Upon trap release and subsequent expansion, we

find that the system displays self-interference fringes. We estimate

characteristic time scales, degree of mass accumulation, three-body loss, and

kinetic energy release during expansion for a typical system of Rb87.

\\ ( http://arXiv.org/abs/cond-mat/0604455 , 216kb)

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Paper: cond-mat/0604458

Date: Wed, 19 Apr 2006 19:30:35 GMT (386kb)

Title: Equations of motion approach to decoherence and current noise in

ballistic interferometers coupled to a quantum bath

Authors: Florian Marquardt

Comments: 10 pages, 7 figures

Subj-class: Mesoscopic Systems and Quantum Hall Effect

\\

We present a technique for treating many particles moving inside a ballistic

interferometer, under the influence of a quantum-mechanical environment

(phonons, photons, Nyquist noise etc.). Our approach is based on solving the

coupled Heisenberg equations of motion of the many-particle system and the bath

and is inspired by the quantum Langevin method known for the Caldeira Leggett

model. It allows to study decoherence and the influence of the bath on other

properties of the interferometer. As a first application, we treat a fermionic

Mach-Zehnder interferometer. In particular, we discuss the dephasing rate and

present full analytical expressions for the leading corrections to the current

noise, brought about by the coupling to the quantum bath.

\\ ( http://arXiv.org/abs/cond-mat/0604458 , 386kb)

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Paper: cond-mat/0504503

replaced with revised version Wed, 19 Apr 2006 08:46:47 GMT (236kb)

Title: Slave particle approach to the finite temperature properties of

ultracold Bose gases in optical lattices

Authors: Xiancong Lu, Jinbin Li and Yue Yu

Comments: 27 pages, 8 figures, final version for publication

Subj-class: Statistical Mechanics

Journal-ref: Phys. Rev. A 73, 043607 (2006)

\\ ( http://arXiv.org/abs/cond-mat/0504503 , 236kb)

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Paper: cond-mat/0602201

replaced with revised version Wed, 19 Apr 2006 01:09:45 GMT (29kb)

Title: Strong coupling theory for the superfluidity of Bose-Fermi mixtures

Authors: Daw-Wei Wang

Comments: 4 pages and 3 figures

Subj-class: Other; Superconductivity

Journal-ref: Phys. Rev. Lett. 96, 140404 (2006)

DOI: 10.1103/PhysRevLett.96.140404

\\ ( http://arXiv.org/abs/cond-mat/0602201 , 29kb)

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Paper: cond-mat/0604063

replaced with revised version Wed, 19 Apr 2006 06:41:16 GMT (12kb)

Title: Disorder-Induced Order: From Classical Spin Systems to Ultracold Atomic

Gases

Authors: Jan Wehr (University Of Arizona), Armand Niederberger (ICFO), Laurent

Sanchez-Palencia (LCFIO), Maciej Lewenstein (ICFO)

Comments: minor changes; references added

Proxy: ccsd ccsd-00022177

Subj-class: Other

\\ ( http://arXiv.org/abs/cond-mat/0604063 , 12kb)

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Paper: quant-ph/0604144

Date: Wed, 19 Apr 2006 15:48:31 GMT (132kb)

Title: Electronic properties of Francium diatomic compounds and prospects for

cold molecule formation

Authors: Mireille Aymar (LAC), Olivier Dulieu (LAC), Fernand Spiegelman (LPQ)

Proxy: ccsd ccsd-00023052

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In this work we investigate the possibility to create cold Fr$\_2$, RbFr, and

CsFr molecules through photoassociation of cold atoms. Potential curves,

permanent and transition dipole moments for the Francium dimer and for the RbFr

and RbCs molecules are determined for the first time. The Francium atom is

modelled as a one valence electron moving in the field of the Fr$^+$ core,

which is described by a new pseudopotential with averaged relativistic effects,

and including effective core polarization potential. The molecular calculations

are performed for both the ionic species Fr$\_2^+$, RbFr$^+$, CsFr$^+$ and the

corresponding neutral, through the CIPSI quantum chemistry package where we

used new extended gaussian basis sets for Rb, Cs, and Fr atoms. As no

experimental data is available, we discuss our results by comparison with the

Rb$\_2$, Cs$\_2$, and RbCs systems. The dipole moment of CsFr reveals an

electron transfer yielding a Cs$^+$Fr$^-$ arrangement, while in all other mixed

alkali pairs the electron is transferred towards the lighter species. Finally

the perturbative treatment of the spin-orbit coupling at large distances

predicts that in contrast with Rb$\_2$ and Cs$\_2$, no double-well excited

potential should be present in Fr$\_2$, probably preventing an efficient

formation of cold dimers via photoassociation of cold Francium atoms.

\\ ( http://arXiv.org/abs/quant-ph/0604144 , 132kb)

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Paper: cond-mat/0604464

Date: Wed, 19 Apr 2006 23:23:40 GMT (117kb)

Title: Quantum theory of an atom laser originating from a Bose-Einstein

condensate or a Fermi gas in the presence of gravity

Authors: Tobias Kramer and Mirta Rodriguez

Comments: 12 pages, 8 figures

Subj-class: Other

\\

We present a 3D quantum mechanical theory of radio-frequency outcoupled atom

lasers from trapped atomic gases in the presence of the gravitational force.

Predictions for the total outcoupling rate as a function of the radio-frequency

and for the beam wave function are given. We establish a sum rule for the

energy integrated outcoupling, which leads to a separate determination of the

coupling strength between the atoms and the radiation field.

For a non-interacting Bose-Einstein condensate analytic solutions are derived

which are subsequently extended to include the effects of atomic interactions.

The interactions enhance interference effects in the beam profile and modify

the outcoupling rate of the atom laser. We provide a complete quantum

mechanical solution which is in line with experimental findings and allows to

determine the validity of commonly used approximative methods.

We also extend the formalism to a fermionic atom laser and analyze the effect

of superfluidity on the outcoupling of atoms.

\\ ( http://arXiv.org/abs/cond-mat/0604464 , 117kb)

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Paper: cond-mat/0604469

Date: Thu, 20 Apr 2006 07:19:00 GMT (109kb)

Title: Finite Temperature Momentum Distribution of a Trapped Fermi Gas

Authors: Qijin Chen, C. A. Regal, D. S. Jin, and K. Levin

Comments: 5 pages, 3 figures

Subj-class: Strongly Correlated Electrons; Superconductivity

\\

We present measurements of the temperature-dependent momentum distribution of

a trapped Fermi gas consisting of $^{40}$K in the BCS-BEC crossover regime.

Accompanying theoretical results based upon a simple mean-field ground state

are compared to the experimental data. Non-monotonic effects associated with

temperature, $T$, arise from the competition between thermal broadening and a

narrowing of the distribution induced by the decrease in the excitation gap

$\Delta(T)$ with increasing $T$.

\\ ( http://arXiv.org/abs/cond-mat/0604469 , 109kb)

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Paper: cond-mat/0604476

Date: Thu, 20 Apr 2006 10:08:52 GMT (155kb)

Title: Relaxation in a completely integrable many-body quantum system: an {\it

ab initio} study of the dynamics of the highly excited states of lattice

hard-core bosons

Authors: Marcos Rigol (1), Vanja Dunjko (2), Vladimir Yurovsky (3), Maxim

Olshanii (2) ((1) UC Davis, (2) USC, (3) U Tel Aviv)

Comments: 4 pages, 2 figures

Subj-class: Other

\\

In this article we pose the question of whether a many-body quantum system

with a full set of conserved quantities can undergo an irreversible relaxation

to an equilibrium state, and, if it can, what this state is. We confirm the

relaxation hypothesis through a thorough ab initio numerical investigation of

the dynamics of hard-core bosons on a one-dimensional lattice. Further, a

natural extension of the Gibbs ensemble to integrable systems results in a

theory that is able to predict the equilibrium state after relaxation. The

theoretical and numerical results are in excellent agreement. Finally, we show

that our generalized equilibrium carries more memory of the initial conditions

than the usual thermodynamic one. This effect may have many experimental

consequences, some of which having already been observed in the recent

experiment on the non-equilibrium dynamics of one-dimensional hard-core bosons

in a harmonic potential [T. Kinoshita, T. Wenger, D.S. Weiss, Nature (London)

440, 900 (2006)].

\\ ( http://arXiv.org/abs/cond-mat/0604476 , 155kb)

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Paper: cond-mat/0603643

replaced with revised version Thu, 20 Apr 2006 13:10:01 GMT (61kb)

Title: The 1D interacting anyon gas: low-energy properties and Haldane

exclusion statistics

Authors: M.T. Batchelor, X.-W. Guan and N. Oelkers

Comments: 4 pages, 2 figures, improved text, references added

Subj-class: Statistical Mechanics

\\ ( http://arXiv.org/abs/cond-mat/0603643 , 61kb)

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-- ------------------------------------------------------------------------- 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/ -------------------------------------------------------------------------Received on Mon Apr 24 2006 - 13:21:59 EST

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