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

Date: Mon, 17 Nov 2008 10:01:53 +1000

Date: Mon, 17 Nov 2008 10:01:53 +1000

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

Hi everyone,

This week there ar 31 new preprints and 11 replacements:

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arXiv:0811.1065

Date: Fri, 7 Nov 2008 00:57:40 GMT (159kb)

Title: Exact ground-state properties of interacting two-component Bose gases in

a hard-wall trap

Authors: Yajiang Hao, Yunbo Zhang, Xi-Wen Guan, Shu Chen

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

Comments: 7 pages, 8 figures

\\

We investigate ground-state properties of interacting two-component Bose

gases in a hard-wall trap using both the Bethe ansatz and exact numerical

diagonalization method. For equal intra- and inter-atomic interaction, the

system is exactly solvable. Thus the exact ground state wavefunction and

density distributions for the whole interacting regime can be obtained from the

Bethe ansatz solutions. Since the ground state is a degenerate state with total

spin S=N/2, the total density distribution are same for each degenerate state.

The total density distribution evolves from a Gauss-like Bose distribution to a

Fermi-like one as the repulsive interaction increases. The distribution of each

component is N_i/N of the total density distribution. This is approximately

true even in the experimental situation. In addition the numerical results show

that with the increase of interspecies interaction the distributions of two

Tonks-Girardeau gases exhibit composite fermionization crossover with each

component developing N peaks in the strongly interacting regime.

\\ ( http://arxiv.org/abs/0811.1065 , 159kb)

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arXiv:0811.1136

Date: Fri, 7 Nov 2008 13:00:07 GMT (271kb,D)

Title: Bose-Einstein condensates in a double well: mean-field chaos and

multi-particle entanglement

Authors: Christoph Weiss, Niklas Teichmann

Categories: cond-mat.other

Comments: 5 Pages, 5 jpg-figures, to be published in the proceedings of the

LPHYS08

\\

A recent publication [Phys. Rev. Lett. 100, 140408 (2008)] shows that there

is a relation between mean-field chaos and multi-particle entanglement for BECs

in a periodically shaken double well. 'Schrodinger-cat' like mesoscopic

superpositions in phase-space occur for conditions for which the system

displays mean-field chaos. In the present manuscript, more general

highly-entangled states are investigated. Mean-field chaos accelerates the

emergence of multi-particle entanglement; the boundaries of stable regions are

particularly suited for entanglement generation.

\\ ( http://arxiv.org/abs/0811.1136 , 271kb)

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arXiv:0811.1159

Date: Fri, 7 Nov 2008 15:42:31 GMT (86kb)

Title: Thermodynamic Measurements in a Strongly Interacting Fermi Gas

Authors: Le Luo and John E. Thomas

Categories: cond-mat.other

Comments: 29 pages, 12 figures. To appear in JLTP online, and in the January,

2009 volume

\\

We conduct a series of measurements on the thermodynamic properties of an

optically-trapped strongly interacting Fermi gas, including the energy $E$,

entropy $S$, and sound velocity $c$. Our model-independent measurements of $E$

and $S$ enable a precision study of the finite temperature thermodynamics. The

$E(S)$ data are directly compared to several recent predictions. The

temperature in both the superfluid and normal fluid regime is obtained from the

fundamental thermodynamic relation $T=\partial E/\partial S$ by parameterizing

the $E(S)$ data. Our $E(S)$ data are also used to experimentally calibrate the

endpoint temperatures obtained for adiabatic sweeps of the magnetic field

between the ideal and strongly interacting regimes. This enables the first

experimental calibration of the temperature scale used in experiments on

fermionic pair condensation. Our calibration shows that the ideal gas

temperature measured for the onset of pair condensation corresponds closely to

the critical temperature estimated in the strongly interacting regime from the

fits to our $E(S)$ data. The results are in very good agreement with recent

predictions. Finally, using universal thermodynamic relations, we estimate the

chemical potential and heat capacity of the trapped gas from the $E(S)$ data.

\\ ( http://arxiv.org/abs/0811.1159 , 86kb)

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arXiv:0811.1188

Date: Fri, 7 Nov 2008 17:33:42 GMT (36kb)

Title: Quasiparticle excitations and dynamic susceptibilities in the BCS-BEC

crossover

Authors: J. Bauer and A.C. Hewson

Categories: cond-mat.supr-con cond-mat.str-el

Comments: 6 pages, 5 figures

\\

We study dynamic ground state properties in the crossover from weak (BCS) to

strong coupling (BEC) superfluidity. Our approach is based on the attractive

Hubbard model which is analyzed by the dynamical mean field theory (DMFT)

combined with the numerical renormalization group (NRG). We present an

extension of the NRG method for effective impurity models to selfconsistent

calculations with superconducting symmetry breaking. In the one particle

spectra we show quantitatively how the Bogoliubov quasiparticles at weak

coupling become suppressed at intermediate coupling. We also present results

for the spin and charge gap. The extension of the NRG method to selfconsistent

superconducting solutions opens the possibility to study a range of other

important applications.

\\ ( http://arxiv.org/abs/0811.1188 , 36kb)

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arXiv:0811.1155

Date: Fri, 7 Nov 2008 14:49:25 GMT (581kb)

Title: Mesoscopic Rydberg Gate based on Electromagnetically Induced

Transparency

Authors: M. M\"uller, I. Lesanovsky, H. Weimer, H. P. B\"uchler, and P. Zoller

Categories: quant-ph

\\

We demonstrate theoretically a parallelized C-NOT gate which allows to

entangle a mesoscopic ensemble of atoms with a single control atom in a single

step, with high fidelity and on a microsecond timescale. Our scheme relies on

the strong and long-ranged interaction between Rydberg atoms triggering

Electromagnetically Induced Transparency (EIT). By this we can robustly

implement a conditional transfer of all ensemble atoms among two logical

states, depending on the state of the control atom. We outline a many body

interferometer which allows a comparison of two many-body quantum states by

performing a measurement of the control atom.

\\ ( http://arxiv.org/abs/0811.1155 , 581kb)

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arXiv:0811.1156

Date: Fri, 7 Nov 2008 14:53:17 GMT (725kb)

Title: Spinor Dynamics of Quantum Accelerator Modes near Higher Order

Resonances

Authors: L. Rebuzzini, I. Guarneri, and R. Artuso

Categories: quant-ph

Comments: 16 pages, 7 figures

\\

Quantum Accelerator Modes were discovered in experiments with Kicked Cold

Atoms in the presence of gravity. They were shown to be tightly related to

resonances of the Quantum Kicked Rotor. In this paper a spinor formalism is

developed for the analysis of Modes associatedwith resonances of arbitrary

order q>1. Decoupling of spin variables from orbital ones is achieved by means

of an ansatz of the Born-Oppenheimer type, that generates q independent band

dynamics. Each of these is described, in classical terms, by a map, and the

stable periodic orbits of this map give rise to quantum accelerator modes,

which are potentially observable in experiments. The arithmetic organization of

such periodic orbits is briefly discussed.

\\ ( http://arxiv.org/abs/0811.1156 , 725kb)

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arXiv:0811.1161

Date: Fri, 7 Nov 2008 15:48:30 GMT (143kb)

Title: Experimental study of vapor-cell magneto-optical traps for efficient

trapping of radioactive atoms

Authors: S. N. Atutov, R. Calabrese, A. Facchini, G. Stancari, L. Tomassetti

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

Comments: 9 pages, 7 figures, submitted to Eur. Phys. J. D

\\

We have studied magneto-optical traps (MOTs) for efficient on-line trapping

of radioactive atoms. After discussing a model of the trapping process in a

vapor cell and its efficiency, we present the results of detailed experimental

studies on Rb MOTs. Three spherical cells of different sizes were used. These

cells can be easily replaced, while keeping the rest of the apparatus

unchanged: atomic sources, vacuum conditions, magnetic field gradients, sizes

and power of the laser beams, detection system. By direct comparison, we find

that the trapping efficiency only weakly depends on the MOT cell size. It is

also found that the trapping efficiency of the MOT with the smallest cell,

whose diameter is equal to the diameter of the trapping beams, is about 40%

smaller than the efficiency of larger cells. Furthermore, we also demonstrate

the importance of two factors: a long coated tube at the entrance of the MOT

cell, used instead of a diaphragm; and the passivation with an alkali vapor of

the coating on the cell walls, in order to minimize the losses of trappable

atoms. These results guided us in the construction of an efficient

large-diameter cell, which has been successfully employed for on-line trapping

of Fr isotopes at INFN's national laboratories in Legnaro, Italy.

\\ ( http://arxiv.org/abs/0811.1161 , 143kb)

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arXiv:0811.1224

Date: Fri, 7 Nov 2008 21:13:17 GMT (726kb)

Title: Superfluid and supersolid phases of lattice bosons with ring-exchange

interaction

Authors: Robert Schaffer, Anton A. Burkov and Roger G. Melko

Categories: cond-mat.str-el cond-mat.supr-con

Comments: 7 pages, 5 figures

\\

We examine the superfluid phase of a hard-core boson model with

nearest-neighbor exchange J and four-particle ring-exchange K at half-filling

on the square lattice. At zero temperature we find that the superfluid in the

pure-J model is quickly destroyed by the inclusion of negative-K ring-exchange

interactions, favoring a state with a (pi,pi) ordering wavevector. Minimization

of the mean-field energy suggests that a supersolid state with coexisting

superfluidity, charge-density wave, and valence-bond-like order is formed. We

also study the behavior of the finite-T Kosterlitz-Thouless phase transition in

the superfluid phase, by forcing the Nelson-Kosterlitz universal jump condition

on the finite-T spin wave superfluid density. Away from the pure J point,

T_{KT} decreases rapidly for negative K, while for positive K, T_{KT} reaches a

maximum at some K \neq 0 in agreement with recent quantum Monte Carlo

simulations.

\\ ( http://arxiv.org/abs/0811.1224 , 726kb)

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arXiv:0811.1233

Date: Fri, 7 Nov 2008 22:30:39 GMT (605kb)

Title: Stability and Excitations of a Dipolar Bose-Einstein Condensate with a

Vortex

Authors: Ryan M. Wilson, Shai Ronen and John L. Bohn

Categories: cond-mat.other

Comments: 18 pages (preprint), 4 figures, submitted to PRA

\\

We study the stability of singly- and doubly-quantized vortex states of

harmonically trapped dipolar Bose-Einstein Condensates (BECs) by calculating

the low-lying excitations of these condensates. We map the dynamical stability

of these vortices as functions of the dipole-dipole interaction strength and

trap geometry by finding where their excitations have purely real energy

eigenvalues. In contrast to BECs with purely contact interactions, we find that

dipolar BECs in singly-quantized vortex states go unstable to modes with an

increasing number of angular and radial nodes for more oblate trap aspect

ratios, corresponding to \emph{local} collapse that occurs on a characteristic

length scale. Additionally, we find that dipolar BECs in doubly-quantized

vortex states are unstable to decay into a different topological state (with

two singly-quantized vortices) for all interaction strengths when the trap

geometry is sufficiently prolate to make the dipoles attractive, and in windows

of interaction strength when the trap geometry is sufficiently oblate to make

the dipoles repulsive.

\\ ( http://arxiv.org/abs/0811.1233 , 605kb)

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arXiv:0811.1280

Date: Sun, 9 Nov 2008 05:09:31 GMT (111kb)

Title: Signatures of the superfluid to Mott insulator transition in cold

bosonic atoms in a one dimensional optical lattice

Authors: S. Ramanan, Tapan Mishra, Meetu Sethi Luthra, Ramesh V. Pai, B. P. Das

Categories: cond-mat.other cond-mat.stat-mech

Comments: 8 pages, 14 figures

\\

We study the Bose-Hubbard model using the finite size density matrix

renormalization group method. We obtain for the first time a complete phase

diagram for a system in the presence of a harmonic trap and compare it with

that of the homogeneous system. To realize the transition from the superfluid

to the Mott insulator phase we investigate different experimental signatures of

these phases in quantities such as momentum distribution, visibility,

condensate fraction and the total number of bosons at a particular density. The

relationships between the various experimental signatures and the phase diagram

are highlighted.

\\ ( http://arxiv.org/abs/0811.1280 , 111kb)

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arXiv:0811.1537

Date: Mon, 10 Nov 2008 18:33:57 GMT (1306kb)

Title: Multiband bosons in optical lattices

Authors: J. Larson, A. Collin, and J.-P. Martikainen

Categories: cond-mat.other

Report-no: NORDITA-2008-50

\\

We study a gas of repulsively interacting bosons in an optical lattice and

explore the physics beyond the lowest band Hubbard model. By including the

lowest band and first excited bands and utilizing a generalized Gutzwiller

ansatz we find how the lowest band physics is modified by the inclusion of the

first excited bands. In contrast to the prediction of the lowest band

Bose-Hubbard model we find a reentrant behavior of superfluidity and decreasing

width of the Mott lobes at strong coupling.

\\ ( http://arxiv.org/abs/0811.1537 , 1306kb)

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arXiv:0811.1243

Date: Mon, 10 Nov 2008 17:15:05 GMT (1654kb)

Title: Squeezed Light and Entangled Images from Four-Wave-Mixing in Hot

Rubidium Vapor

Authors: Raphael C Pooser, Vincent Boyer, Alberto M. Marino, Paul D. Lett

Categories: quant-ph

Comments: 11 pages, 8 figures. SPIE Optics and Photonics 2008 proceeding (San

Diego, CA)

\\

Entangled multi-spatial-mode fields have interesting applications in quantum

information, such as parallel quantum information protocols, quantum computing,

and quantum imaging. We study the use of a nondegenerate four-wave mixing

process in rubidium vapor at 795 nm to demonstrate generation of

quantum-entangled images. Owing to the lack of an optical resonator cavity, the

four-wave mixing scheme generates inherently multi-spatial-mode output fields.

We have verified the presence of entanglement between the multi-mode beams by

analyzing the amplitude difference and the phase sum noise using a dual

homodyne detection scheme, measuring more than 4 dB of squeezing in both cases.

This paper will discuss the quantum properties of amplifiers based on

four-wave-mixing, along with the multi mode properties of such devices.

\\ ( http://arxiv.org/abs/0811.1243 , 1654kb)

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arXiv:0811.1269

Date: Sat, 8 Nov 2008 15:45:17 GMT (701kb)

Title: Weakly interacting Bose gas in a random environment

Authors: G.M. Falco, T. Nattermann and V.L. Pokrovsky

Categories: quant-ph

\\

Zero temperature properties of a dilute weakly interacting $d$-dimensional

Bose gas in a random potential are studied. We calculate geometrical and

energetic characteristics of the localized state of a gas confined in a large

box or in a harmonic trap. Different regimes of the localized state are found

depending on the ratio of two characteristic length scales of the disorder, the

Larkin length and the disorder correlation length. Repulsing bosons confined in

a large box with average density $n$ well below a critical value $n_c$ are

trapped in deep potential wells of extension much smaller than distance between

them. Tunneling between these wells is exponentially small. The ground state of

such a gas is a random singlet with no long-range phase correlation For $n>n_c$

repulsion between particles overcomes the disorder and the gas transits from

the localized to a coherent superfluid state. The critical density $n_c$ is

calculated in terms of the disorder parameters and the interaction strength.

For atoms in traps four different regimes are found, only one of it is

superfluid. The theory is extended to lower (1 and 2) dimensions. Its

quantitative predictions can be checked in experiments with ultracold atomic

gases and other Bose-systems.

\\ ( http://arxiv.org/abs/0811.1269 , 701kb)

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arXiv:0811.1401

Date: Mon, 10 Nov 2008 06:26:00 GMT (875kb)

Title: Fermions on atom chips

Authors: Marcius H. T. Extavour, Lindsay J. LeBlanc, Jason McKeever, Alma B.

Bardon, Seth Aubin, Stefan Myrskog, Thorsten Schumm and Joseph H. Thywissen

Categories: quant-ph

Comments: 33 pages, 10 figures

\\

We review our recent and ongoing work with Fermi gases on an atom chip. After

reviewing some statistical and thermodynamic properties of the ideal,

non-interacting Fermi gas, and a brief description of our atom chip and its

capabilities, we discuss our experimental approach to producing a potassium-40

degenerate Fermi gas (DFG) using sympathetic cooling by a rubidium-87

Bose-Einstein condensate on an atom chip. In doing so, we describe the factors

affecting the loading efficiency of the atom chip microtrap. This is followed

by a discussion of species selectivity in radio frequency manipulation of the

Bose-Fermi mixture, which we explore in the context of sympathetic evaporative

cooling and radio-frequency dressed adiabatic double-well potentials. Next, we

describe the incorporation of a crossed-beam dipole trap into the atom chip

setup, in which we generate and manipulate strongly interacting spin mixtures

of potassium-40. Finally, we conclude with a brief discussion of future

research directions with DFGs and atom chips. This article is to be included in

a forthcoming, broader volume on atom chips.

\\ ( http://arxiv.org/abs/0811.1401 , 875kb)

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arXiv:0811.1550

Date: Mon, 10 Nov 2008 19:19:17 GMT (437kb)

Title: Suppression or enhancement of the Fulde-Ferrell-Larkin-Ovchinnikov order

in a one-dimensional optical lattice with particle correlated tunnelling

Authors: B. Wang and L.-M. Duan

Categories: quant-ph

\\

We study through controlled numerical simulation the ground state properties

of spin-polarized strongly interacting fermi gas in an anisotropic optical

lattice, which is described by an effective one-dimensional general Hubbard

model with particle correlated hopping rate. We show that the

Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type of state, while enhanced by a

negative correlated hopping rate, can be completely suppressed by positive

particle correlated hopping, yielding to an unusual magnetic phase even for

particles with on-site attractive interaction We also find several different

phase separation patterns for these atoms in an inhomogeneous harmonic trap,

depending on the correlated hopping rate.

\\ ( http://arxiv.org/abs/0811.1550 , 437kb)

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arXiv:0811.1615

Date: Tue, 11 Nov 2008 02:04:25 GMT (1651kb)

Title: Casimir interaction among heavy fermions in the BCS-BEC crossover

Authors: Yusuke Nishida

Categories: cond-mat.other

Comments: 10 pages, 6 figures

Report-no: MIT-CTP 3996

\\

We investigate a two-species Fermi gas with a large mass ratio interacting by

an interspecies short-range interaction. Using the Born-Oppenheimer

approximation, we determine the interaction energy of two heavy fermions

immersed in the Fermi sea of light fermions as a function of the s-wave

scattering length. In the BCS limit, we recover the perturbative calculation of

the effective interaction between heavy fermions. The p-wave projection of the

effective interaction is attractive in the BCS limit while it turns out to be

repulsive near the unitarity limit. We find that the p-wave attraction reaches

its maximum between the BCS and unitarity limits, where the maximal p-wave

pairing of heavy minority fermions is expected. We also investigate the case

where the heavy fermions are confined in two dimensions and the p-wave

attraction between them is found to be stronger than that in three dimensions.

\\ ( http://arxiv.org/abs/0811.1615 , 1651kb)

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arXiv:0811.1660

Date: Tue, 11 Nov 2008 09:44:12 GMT (26kb)

Title: Entropy entrainment and dissipation in superfluid Helium

Authors: N. Andersson and G.L. Comer

Categories: cond-mat.other

\\

We discuss finite temperature effects in superfluid Helium, providing a

direct demonstration that a model based on treating the excitations in the

system as a massless "entropy" fluid is equivalent to the traditional two-fluid

approach. In particular, we demonstrate how the entropy entrainment is related

to the "normal fluid density". We also show how the superfluid constraint of

irrotationality reduces the number of dissipation coefficients in the system.

This analysis provides insight into the more general problem when vortices are

present in the superfluid, and we discuss how the so-called mutual friction

force can be accounted for. The end product is a formalism for finite

temperature effects in a single condensate that can be applied to Helium in the

low temperature regime. It can also be used to describe (to a certain extent)

colour-flavour locked quark superconductors that may be present at the extreme

densities in a neutron star core.

\\ ( http://arxiv.org/abs/0811.1660 , 26kb)

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arXiv:0811.1672

Date: Tue, 11 Nov 2008 10:22:41 GMT (78kb)

Title: Free-fall expansion of finite-temperature Bose-Einstein condensed gas in

the non Thomas-Fermi regime

Authors: M. Zawada, R. Abdoul, J. Chwede\'nczuk, R. Gartman, J. Szczepkowski,

L. Tracewski, M. Witkowski, W. Gawlik

Categories: cond-mat.other

Comments: 8 pages, 4 figures

\\

We report on our study of the free-fall expansion of a finite-temperature

Bose-Einstein condensed cloud of 87Rb. The experiments are performed with a

variable total number of atoms while keeping constant the number of atoms in

the condensate. The results provide evidence that the BEC dynamics depends on

the interaction with thermal fraction. In particular, they provide experimental

evidence that thermal cloud compresses the condensate.

\\ ( http://arxiv.org/abs/0811.1672 , 78kb)

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arXiv:0811.1737

Date: Tue, 11 Nov 2008 17:16:59 GMT (32kb)

Title: Towards A Possible Charge-Kondo effect in Optical Lattices

Authors: M.S. Laad and A. Taraphder

Categories: cond-mat.str-el cond-mat.supr-con

Comments: submitted to Phys. Rev. Lett

\\

The Kondo effect underpins a large body of recent developments in the physics

of $d$- and $f$-band compounds. Although its {\it charge} analog is a rarity in

solids, the recent observations of the charge Kondo effect and the consequent

rise in superconducting T$_c$ encourage a search for other accessible systems.

Motivated by the possibility of wilfully tuning the {\it sign} of the

inter-electronic interaction in optical lattices, we study conditions for the

elusive {\it charge Kondo liquid} (CKL) state to manifest. We propose that a

combination of Feshbach resonances and sequentially controlled laser pulses may

produce the CKL. We show that the CKL is {\it never} a stable ground state,

appearing only when the ordered ground states are destabilized. Finally, we

discuss interesting analogies with nuclear matter.

\\ ( http://arxiv.org/abs/0811.1737 , 32kb)

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arXiv:0811.1166 (*cross-listing*)

Date: Fri, 7 Nov 2008 16:04:45 GMT (24kb)

Title: The ground state energy of the weakly interacting Bose gas at high

density

Authors: Alessandro Giuliani, Robert Seiringer

Categories: math-ph cond-mat.stat-mech math.MP

Comments: RevTeX4, 16 pages

\\

We prove the Lee-Huang-Yang formula for the ground state energy of the 3D

Bose gas with repulsive interactions described by the exponential function, in

a simultaneous limit of weak coupling and high density. In particular, we show

that the Bogoliubov approximation is exact in an appropriate parameter regime,

as far as the ground state energy is concerned.

\\ ( http://arxiv.org/abs/0811.1166 , 24kb)

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arXiv:0811.1605

Date: Tue, 11 Nov 2008 00:04:53 GMT (70kb)

Title: Reactive Collisions of Ultracold Molecules Confined in quasi-2D Geometry

Authors: Z. Li and R. V. Krems

Categories: physics.atom-ph physics.chem-ph

Comments: 4pages

\\

We present a formalism for rigorous calculations of cross sections for

reactive collisions of ultracold atoms and molecules confined by laser fields

in quasi-2D geometry. We use the method to elucidate the general features of

inelastic scattering and chemical reactions in ultracold quasi-2D gases. Our

results indicate that the elastic-to-inelastic ratios of collision cross

sections are generally enhanced in the presence of a laser confinement and that

the threshold energy dependence of the collision cross sections can be tuned by

varying the confinement strength and external magnetic fields.

\\ ( http://arxiv.org/abs/0811.1605 , 70kb)

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arXiv:0811.1873

Date: Wed, 12 Nov 2008 11:48:48 GMT (1304kb)

Title: Density profiles of polarized Fermi gases confined in harmonic traps

Authors: G. Bertaina and S. Giorgini

Categories: cond-mat.other cond-mat.supr-con

Comments: 6 pages, 4 figures

\\

On the basis of the phase diagram of the uniform system we calculate the

density profiles of a trapped polarized Fermi gas at zero temperature using the

local density approximation. By varying the overall polarization and the

interaction strength we analyze the appearance of a discontinuity in the

profile, signalling a first order phase transition from a superfluid inner core

to a normal outer shell. The local population imbalance between the two

components and the size of the various regions of the cloud corresponding to

different phases are also discussed. The calculated profiles are quantitatively

compared with the ones recently measured by Shin {\it et al.}, Phys. Rev. Lett.

{\bf 101}, 070404 (2008).

\\ ( http://arxiv.org/abs/0811.1873 , 1304kb)

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arXiv:0811.1891

Date: Wed, 12 Nov 2008 13:18:53 GMT (804kb)

Title: Wave patterns generated by a supersonic moving body in a binary

Bose-Einstein condensate

Authors: Yu. G. Gladush, A. M. Kamchatnov, Z. Shi, P. G. Kevrekidis, D. J.

Frantzeskakis, B. A. Malomed

Categories: cond-mat.other

Comments: 13 pages, 6 figures

\\

Generation of wave structures by a two-dimensional object (laser beam) moving

in a two-dimensional two-component Bose-Einstein condensate with a velocity

greater than both sound velocities of the mixture is studied by means of

analytical methods and systematic simulations of the coupled Gross-Pitaevskii

equations. The wave pattern features three regions separated by two Mach cones.

Two branches of linear patterns similar to the so-called "ship waves" are

located outside the corresponding Mach cones, and oblique dark solitons are

found inside the wider cone. An analytical theory is developed for the linear

patterns. A particular dark-soliton solution is also obtained, its stability is

investigated, and two unstable modes of transverse perturbations are

identified. It is shown that, for a sufficiently large flow velocity, this

instability has a convective character in the reference frame attached to the

moving body, which makes the dark soliton effectively stable. The analytical

findings are corroborated by numerical simulations.

\\ ( http://arxiv.org/abs/0811.1891 , 804kb)

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arXiv:0811.1921

Date: Wed, 12 Nov 2008 15:44:34 GMT (152kb)

Title: Symmetry-Breaking and Symmetry-Restoring Dynamics of a Mixture of

Bose-Einstein Condensates in a Double Well

Authors: Indubala I Satija and Philip Naudus (George Mason University, Fairfax,

VA), Radha Balakrishnan (Institute of Mathematical Sciences, Chennai, India),

Jeffrey Heward, Mark Edwards (Department of Physics, Georgia Southern

University, Statesboro, GA) and and Charles W Clark (National Institute of

Standards and Technology, Gaithersburg, Maryland)

Categories: quant-ph

\\

We study the coherent nonlinear tunneling dynamics of a binary mixture of

Bose-Einstein condensates in a double-well potential. We demonstrate the

existence of a new type of mode associated with the "swapping" of the two

species in the two wells of the potential. In contrast to the symmetry breaking

macroscopic quantum self-trapping (MQST) solutions, the swapping modes

correspond to the tunneling dynamics that preserves the symmetry of the double

well potential. As a consequence of two distinct types of broken symmetry MQST

phases where the two species localize in the different potential welils or

coexist in the same well, the corresponding symmetry restoring swapping modes

result in dynamics where the the two species either avoid or chase each other.

In view of the possibility to control the interaction between the species, the

binary mixture offers a very robust system to observe these novel effects as

well as the phenomena of Josephson oscillations and pi-modes

\\ ( http://arxiv.org/abs/0811.1921 , 152kb)

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arXiv:0811.1942

Date: Wed, 12 Nov 2008 16:44:01 GMT (383kb)

Title: Matter-Wave Solitons in the Presence of Collisional Inhomogeneities:

Perturbation theory and the impact of derivative terms

Authors: S. Middelkamp, P.G. Kevrekidis, D.J. Frantzeskakis, P. Schmelcher

Categories: quant-ph

Comments: 12 pages, 5 fugures

\\

We study the dynamics of bright and dark matter-wave solitons in the presence

of a spatially varying nonlinearity. When the spatial variation does not

involve zero crossings, a transformation is used to bring the problem to a

standard nonlinear Schrodinger form, but with two additional terms: an

effective potential one and a non-potential term. We illustrate how to apply

perturbation theory of dark and bright solitons to the transformed equations.

We develop the general case, but primarily focus on the non-standard special

case whereby the potential term vanishes, for an inverse square spatial

dependence of the nonlinearity. In both cases of repulsive and attractive

interactions, appropriate versions of the soliton perturbation theory are shown

to accurately describe the soliton dynamics.

\\ ( http://arxiv.org/abs/0811.1942 , 383kb)

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arXiv:0811.1816

Date: Wed, 12 Nov 2008 05:29:52 GMT (155kb)

Title: Measuring the frequency of a Sr optical lattice clock using a 120-km

coherent optical transfer

Authors: F.-L. Hong, M. Musha, M. Takamoto, H. Inaba, S. Yanagimachi, A.

Takamizawa, K. Watabe, T. Ikegami, M. Imae, Y. Fujii, M. Amemiya, K.

Nakagawa, K. Ueda, and H. Katori

Categories: physics.atom-ph physics.optics

Comments: 14 pages, 3 figures

\\

We demonstrate a precision frequency measurement using a phase-stabilized

120-km optical fiber link over a physical distance of 50 km. The transition

frequency of the 87Sr optical lattice clock at the University of Tokyo is

measured to be 429228004229874.1(2.4) Hz referenced to international atomic

time (TAI). The measured frequency agrees with results obtained in Boulder and

Paris at a 6*10^-16 fractional level, which matches the current best

evaluations of Cs primary frequency standards. The results demonstrate the

excellent functions of the intercity optical fibre link, and the great

potential of optical lattice clocks for use in the redefinition of the second.

\\ ( http://arxiv.org/abs/0811.1816 , 155kb)

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\\

arXiv:0811.2054

Date: Thu, 13 Nov 2008 09:32:21 GMT (19kb)

Title: Cooling into the Spin-Nematic State for a Spin-1 Bose gase in an optical

lattice

Authors: Ming-Chiang Chung and Sungkit Yip

Categories: cond-mat.other

Comments: 2 figures

\\

The possibility of adiabatically cooling a spin-1 polar Bose gas to a

spin-nematic phase is theoretically discussed. The relation between the order

parameter of the final spin-nematic phase and the starting temperature of the

spinor Bose gas is obtained both using the mean-field approach for the high

temperature and spin-wave approach for the low temperature. We find that there

exists a good possibility to reach the spin-nematic ordering starting with

spinor antiferromagnetic Bose gases.

\\ ( http://arxiv.org/abs/0811.2054 , 19kb)

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\\

arXiv:0811.2078

Date: Thu, 13 Nov 2008 10:56:11 GMT (619kb)

Title: The canonical heat capacity of normal mesoscopic fermion systems: the

temperature evolution and particle number oscillations

Authors: N. K. Kuzmenko and V. M.Mikhajlov

Categories: cond-mat.stat-mech cond-mat.mes-hall

Comments: 44 pages, 25 figures, to appear in Statistical Mechanics (Nova

Science Publishers, N.Y., USA) 2008

\\

The heat capacity (C) of a mesoscopic nonsuperconducting fermion system

treated as a canonical ensemble of independent particles is studied in a wide

range of particle numbers and temperatures which vary from values close to zero

up to the Fermi energy. The temperature evolution of C is naturally divided

into four stages. On the first one the heat capacity exponentially increases

with temperature and at a resonance temperature reaches either a local maximum

or an irregularity in its growth. This resonance temperature being measured can

give information concerning the level spacings in the immediate proximity of

the Fermi energy. On the second stage the progressive suppression of the level

density oscillations takes place. During this stage oscillations of C v.s.

particle number N can be distinctly observed. These oscillations give the

N-variations of the temperature averaged level density. The growth of C on the

third stage of the evolution is governed by the T-linear law if the particle

number is large enough (N>1000). It is found that the Sommerfeld factor in the

linear law for such small systems shows more complicated N-dependence as

compared with large systems where C is strictly proportional to N. For

temperatures tending to the Fermi energy the deviations from the T-linearity

are evident and at T larger than the Fermi energy (the fourth stage of the

evolution) any system attains to the classic Boltzmann-Maxwell limit

irrespective of the particle

\\ ( http://arxiv.org/abs/0811.2078 , 619kb)

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\\

arXiv:0811.2030

Date: Thu, 13 Nov 2008 04:51:43 GMT (547kb)

Title: A comparative study of dynamical simulation methods for the dissociation

of molecular Bose-Einstein condensates

Authors: S. L. W. Midgley, S. Wuester, M. K. Olsen, M. J. Davis and K. V.

Kheruntsyan

Categories: quant-ph

Comments: 11 pages, 7 figures

\\

We describe a pairing mean-field theory related to the

Hartree-Fock-Bogoliubov approach, and apply it to the dynamics of dissociation

of a molecular Bose-Einstein condensate (BEC) into correlated bosonic atom

pairs. We also perform the same simulation using two stochastic phase-space

techniques for quantum dynamics -- the positive P-representation method and the

truncated Wigner method. By comparing the results of our calculations we are

able to assess the relative strength of these theoretical techniques in

describing molecular dissociation in one spatial dimension. An important aspect

of our analysis is the inclusion of atom-atom interactions which can be

problematic for the positive-P method. We find that the truncated Wigner method

mostly agrees with the positive-P simulations, but can be simulated for

significantly longer times. The pairing mean-field theory results diverge from

the quantum dynamical methods after relatively short times.

\\ ( http://arxiv.org/abs/0811.2030 , 547kb)

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\\

arXiv:0811.2139

Date: Thu, 13 Nov 2008 15:44:33 GMT (1292kb,D)

Title: Coherent state approach to the cross collisional effects in the

population dynamics of a two-mode Bose-Einstein condensate

Authors: Thiago F. Viscondi, K. Furuya and M. C. de Oliveira

Categories: quant-ph

Comments: 19 pages, 8 figures

\\

We reanalyze the non-linear population dynamics of a Bose-Einstein Condensate

(BEC) in a double well trap considering a semiclassical approach based on a

time dependent variational principle applied to coherent states associated to

SU(2) group. Employing a two-mode local approximation and hard sphere type

interaction, we show in the Schwinger's pseudo-spin language the occurrence of

a fixed point bifurcation that originates a separatrix of motion on a sphere.

This separatrix corresponds to the borderline between two dynamical regimes of

Josephson oscillations and mesoscopic self-trapping. We also consider the

effects of interaction between particles in different wells, known as cross

collisions. Such terms are usually neglected for traps sufficiently far apart,

but recently it has been shown that they contribute to the effective tunneling

constant with a factor growing linearly with the particle number. This effect

changes considerably the effective tunneling of the system for sufficiently

large number of trapped atoms, in perfect accord with experimental data.

Finally, we identify analytically the transition parameter associated to the

bifurcation in the generalized phase space of the model with cross-collision

terms, and show how the dynamical regime depends on the initial conditions of

the system and the collisional parameters values.

\\ ( http://arxiv.org/abs/0811.2139 , 1292kb)

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\\

arXiv:0811.2183

Date: Thu, 13 Nov 2008 17:42:00 GMT (293kb)

Title: Laser frequency stabilization to highly excited state transitions using

electromagnetically induced transparency in a cascade system

Authors: R. P. Abel, A. K. Mohapatra, M. G. Bason, J. D. Pritchard, K. J.

Weatherill, U. Raitzsch and C. S. Adams

Categories: quant-ph

Comments: 3 pages, 4 figures

\\

We demonstrate laser frequency stabilization to excited state transitions

using cascade electromagnetically induced transparency (EIT). Using a room

temperature Rb vapor cell as a reference, we stabilize a first diode laser to

the D2 transition and a second laser to a transition from the intermediate

state to a Rydberg state with principal quantum number n=19 - 70. A combined

laser linewidth of 280 kHz over a 0.1 ms time period is achieved. This method

may be applied generally to any cascade system and allows laser stabilization

to an atomic reference in the absence of strong optical transitions.

\\ ( http://arxiv.org/abs/0811.2183 , 293kb)

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The replacements:

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arXiv:cond-mat/0512016

replaced with revised version Thu, 6 Nov 2008 22:57:27 GMT (10kb)

Title: The Rayleigh-Taylor Instability in a Bose-Einstein Condensate

Authors: Swarbhanu Chatterjee

Categories: cond-mat.mes-hall cond-mat.mtrl-sci

Comments: 5 pages. One reference in the introduction of the previous version

has been deleted as not being relevant to the paper. The physical formulation

is unchanged except for one point of difference - the initial state in which

the condensate is prepared is different. The presentation of the paper has

been changed

\\ ( http://arxiv.org/abs/cond-mat/0512016 , 10kb)

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\\

arXiv:0805.4261

replaced with revised version Fri, 7 Nov 2008 02:10:17 GMT (1037kb)

Title: Mott Phase in Polarized Two-component Atomic Fermi Lattice Gas:A

Playground for S=1/2 Heisenberg Model in Magnetic Field

Authors: M. Machida, M. Okumura, S. Yamada, T. Deguchi, Y. Ohashi, H. Matsumoto

Categories: cond-mat.str-el

\\ ( http://arxiv.org/abs/0805.4261 , 1037kb)

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\\

arXiv:0809.0040

replaced with revised version Fri, 7 Nov 2008 02:09:20 GMT (217kb)

Title: Phase Separation in two-Species Atomic Bose-Einstein Condensate with

Interspecies Feshbach Resonance

Authors: Lu Zhou, Jing Qian, Han Pu, Weiping Zhang, and Hong Y. Ling

Categories: cond-mat.mes-hall cond-mat.other

Comments: 9 pages, 3 figures

Journal-ref: Phys. Rev. A 78, 053612 (2008)

DOI: 10.1103/PhysRevA.78.053612

\\ ( http://arxiv.org/abs/0809.0040 , 217kb)

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\\

arXiv:0809.1816

replaced with revised version Fri, 7 Nov 2008 16:21:19 GMT (101kb)

Title: Casimir Energy of a BEC: From Moderate Interactions to the Ideal Gas

Authors: J\"urgen Schiefele, Carsten Henkel

Categories: cond-mat.other

Comments: 12 pages, 3 figures, accepted for publication in JPA. New version

with corrected typos and an additional appendix

\\ ( http://arxiv.org/abs/0809.1816 , 101kb)

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\\

arXiv:0707.1302

replaced with revised version Mon, 10 Nov 2008 20:58:06 GMT (363kb)

Title: Possibility of supersolid with repulsive fermions in an anisotropic

optical lattice near a Feshbach resonance

Authors: B. Wang and L.-M. Duan

Categories: cond-mat.other cond-mat.str-el

Comments: updated with published version

Journal-ref: New Journal of Physics 10, 073007 (2008)

\\ ( http://arxiv.org/abs/0707.1302 , 363kb)

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\\

arXiv:0805.3388

replaced with revised version Sun, 9 Nov 2008 01:01:18 GMT (53kb)

Title: Threshold for Chaos and Thermalization in One-Dimensional Mean-Field

Bose-Hubbard Model

Authors: Amy C. Cassidy, Douglas Mason, Vanja Dunjko, Maxim Olshanii

Categories: cond-mat.other cond-mat.stat-mech

Comments: 4 pages, 3 figures

\\ ( http://arxiv.org/abs/0805.3388 , 53kb)

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\\

arXiv:0806.2862

replaced with revised version Fri, 7 Nov 2008 22:29:41 GMT (24kb)

Title: Microscopic diagonal entropy and its connection to basic thermodynamic

relations

Authors: Roman Barankov and Anatoli Polkovnikov

Categories: cond-mat.stat-mech hep-th quant-ph

Comments: minor changes, added references

\\ ( http://arxiv.org/abs/0806.2862 , 24kb)

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\\

arXiv:0804.1277

replaced with revised version Tue, 11 Nov 2008 19:23:40 GMT (8kb)

Title: Hydrodynamics of Bose and Fermi superfluids at zero temperature: the

superfluid nonlinear Schrodinger equation

Authors: Luca Salasnich (CNR-INFM and CNISM, University of Padua)

Categories: cond-mat.stat-mech cond-mat.other

Comments: 4 pages, no figures, prepared for the Special Issue of Laser Physics:

Physics of Cold Trapped Atoms; in the second version corrected some typos; in

the third version added some useful comments. To be published in Laser

Physics (April 2009)

\\ ( http://arxiv.org/abs/0804.1277 , 8kb)

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\\

arXiv:0807.5072 (*cross-listing*)

replaced with revised version Tue, 11 Nov 2008 16:00:44 GMT (40kb)

Title: Not to normal order - Notes on the kinetic limit for weakly interacting

quantum fluids

Authors: Jani Lukkarinen, Herbert Spohn

Categories: math-ph math.MP quant-ph

Comments: 43 pages, corrected typos, updated assumptions in sec. 7

MSC-class: 82C10; 82C40

\\ ( http://arxiv.org/abs/0807.5072 , 40kb)

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\\

arXiv:0811.1188

replaced with revised version Wed, 12 Nov 2008 17:24:46 GMT (36kb)

Title: Quasiparticle excitations and dynamic susceptibilities in the BCS-BEC

crossover

Authors: J. Bauer and A.C. Hewson

Categories: cond-mat.supr-con cond-mat.str-el

Comments: 6 pages, 5 figures (minor amendment and additional reference)

\\ ( http://arxiv.org/abs/0811.1188 , 36kb)

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\\

arXiv:0712.1891

replaced with revised version Thu, 13 Nov 2008 19:15:39 GMT (184kb,D)

Title: Stabilization of Solitons Generated by a Supersonic Flow of

Bose-Einstein Condensate Past an Obstacle

Authors: A.M. Kamchatnov, L.P. Pitaevskii

Categories: cond-mat.other nlin.PS

Comments: 5 pages, 3 figures, final version published in Phys. Rev. Lett

Journal-ref: Phys. Rev. Lett. 100, 160402 (2008)

\\ ( http://arxiv.org/abs/0712.1891 , 184kb)

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Till next time,

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/ ========================================================================= 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 =========================================================================Received on Mon Nov 17 2008 - 13:01:20 EST

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