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

Date: Tue, 31 Jul 2007 15:50:52 +1000 (EST)

Date: Tue, 31 Jul 2007 15:50:52 +1000 (EST)

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

Hi all,

There were 35 new preprints and 13 replacements this week.

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arXiv:0707.1884

Date: Thu, 12 Jul 2007 21:16:14 GMT (10kb)

Title: Soluble Models of Strongly Interacting Two-level Ultracold Gases in

Tight Waveguides with Coupling to the Quantized Electromagnetic Field

Authors: M. D. Girardeau

Categories: cond-mat.other

Comments: 4 pages, no figures, revtex4. Submitted to Phys. Rev. Lett

\\

A generalized Fermi-Bose mapping method is used to determine the exact ground

states of six models of strongly interacting ultracold gases of two-level atoms

in tight waveguides, which are generalizations of the Tonks-Girardeau (TG) gas

(1D Bose gas with point hard cores) and fermionic Tonks-Girardeau (FTG) gas (1D

spin-aligned Fermi gas with infinitely strong zero-range attractions). Three of

these models exhibit a quantum phase transition in the presence of an external

magnetic field, associated with a cooperative ground state rearrangement

wherein Fermi energy is traded for internal excitation energy. After

investigation of these models in the absence of an electromagnetic field, one

is generalized to include resonant interactions with a single photon mode,

leading to a possible thermal phase transition associated with Dicke

superradiance.

\\ ( http://arxiv.org/abs/0707.1884 , 10kb)

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arXiv:0707.1931

Date: Fri, 13 Jul 2007 06:59:59 GMT (120kb)

Title: Shear viscosity and Bose statistics: Capillary flow above lambda point

Authors: Shun-ichiro Koh

Categories: cond-mat.supr-con cond-mat.stat-mech

Comments: 32pages, 7figures

\\

The gradual fall of the shear viscosity below 2.8K, observed in a liquid

helium 4 flowing through a capillary, is examined. The disappearance of the

shear viscosity in a capillary flow is a manifestation of superfluidity in

dissipative phenomena, the onset mechanism of which is a subtle problem

compared to that of superfluidity in non-dissipative phenomena. Applying the

linear-response theory to the reciprocal of the shear viscosity coefficient, we

relate these two types of superfluidity using the Kramers-Kronig relation. We

obtain a formula describing the influence of Bose statistics on the kinematic

shear viscosity in terms of the susceptibility. Compared to an ordinary liquid,

a liquid helium 4 above the lambda point has a 1/1000 times smaller shear

viscosity coefficient. Hence, although in the normal phase, it is already an

anomalous liquid under the strong influence of Bose statistics. The coherent

many-body wave function grows to an intermediate size between a macroscopic and

a microscopic one, not as a thermal fluctuation but as a thermal equilibrium

state. Beginning with bosons without the condensate, we make a perturbation

calculation of its susceptibility with respect to the repulsive interaction. We

examine how, with decreasing temperature, the growth of the coherent wave

function gradually suppresses the shear viscosity, and finally leads to a

frictionless flow at the lambda-point.

\\ ( http://arxiv.org/abs/0707.1931 , 120kb)

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arXiv:0707.1956

Date: Fri, 13 Jul 2007 16:54:31 GMT (21kb)

Title: Nonlinear coherent transport of waves in disordered media

Authors: Thomas Wellens, Benoit Gremaud

Categories: cond-mat.mes-hall cond-mat.dis-nn

Comments: 4 pages, 3 figures

\\

We present a diagrammatic theory for coherent backscattering from disordered

dilute media in the nonlinear regime. The approach is non-perturbative in the

strength of the nonlinearity. We show that the coherent backscattering

enhancement factor is strongly affected by the nonlinearity, and corroborate

these results by numerical simulations. Our theory can be applied to several

physical scenarios like scattering of light in nonlinear Kerr media, or

propagation of matter waves in disordered potentials.

\\ ( http://arxiv.org/abs/0707.1956 , 21kb)

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arXiv:0707.1979

Date: Fri, 13 Jul 2007 11:32:34 GMT (354kb)

Title: Interacting bosons in an optical lattice

Authors: Ch. Moseley, O. Fialko, K. Ziegler

Categories: cond-mat.other

Comments: 58 pages, 14 figures

\\

Several models of a strongly interacting Bose gas in an optical lattice are

studied within the functional-integral approach. The one-dimensional Bose gas

is briefly discussed. Then the Bose-Einstein condensate and the Mott insulator

of a three-dimensional Bose gas are described in mean-field approximation, and

the corresponding phase diagrams are evaluated. Other characteristic

quantities, like the spectrum of quasiparticle excitations and the static

structure factor, are obtained from Gaussian fluctuations around the mean-field

solutions. We discuss the role of quantum and thermal fluctuations, and

determine the behavior of physical quantities in terms of density and

temperature of the Bose gas. In particular, we study the dilute limit, where

the mean-field equation becomes the Gross-Pitaevskii equation. This allows us

to extend the Gross-Pitaevskii equation to the dense regime by introducing

renormalized parameters in the latter.

\\ ( http://arxiv.org/abs/0707.1979 , 354kb)

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arXiv:0707.1980

Date: Fri, 13 Jul 2007 11:38:57 GMT (153kb)

Title: Atomic Landau-Zener tunneling in Fourier-synthesized optical lattices

Authors: Tobias Salger, Carsten Geckeler, Sebastian Kling, Martin Weitz

Categories: cond-mat.other

Comments: 11 pages, 5 figures

\\

We report on an experimental study of quantum transport of atoms in variable

periodic optical potentials. The band structure of both ratchet-type asymmetric

and symmetric lattice potentials is explored. The variable atom potential is

realized by superimposing a conventional standing wave potential of \lambda/2

spatial periodicity with a fourth-order multiphoton potential of \lambda /4

periodicity. We find that the Landau-Zener tunneling rate between the first and

the second excited Bloch band depends critically on the relative phase between

the two spatial lattice harmonics.

\\ ( http://arxiv.org/abs/0707.1980 , 153kb)

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arXiv:0707.1993

Date: Fri, 13 Jul 2007 12:50:48 GMT (20kb)

Title: Decoherence of a particle in a ring

Authors: Doron Cohen and Baruch Horovitz

Categories: cond-mat.mes-hall

Comments: 5 pages, 1 figure

\\

We consider a particle coupled to a dissipative environment and derive a

perturbative formula for the dephasing rate based on the purity of the reduced

probability matrix. We apply this formula to the problem of a particle on a

ring, that interacts with a dirty metal environment. At low but finite

temperatures we find a dephasing rate $\propto T^{3/2}$, and identify dephasing

lengths for large and for small rings. These findings shed light on recent

Monte Carlo data regarding the effective mass of the particle. At zero

temperature we find that spatial fluctuations suppress the possibility of

having a power law decay of coherence.

\\ ( http://arxiv.org/abs/0707.1993 , 20kb)

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arXiv:0707.1971

Date: Fri, 13 Jul 2007 11:00:51 GMT (188kb)

Title: Observation of Electromagnetically Induced Transparency for a Squeezed

Vacuum with the Time Domain Method

Authors: M. Arikawa, K. Honda, D. Akamatsu, Y. Yokoi, K. Akiba, S. Nagatsuka,

A. Furusawa, and M. Kozuma

Categories: quant-ph

\\

A probe light in a squeezed vacuum state was injected into cold 87Rb atoms

with an intense control light in a coherent state. A sub-MHz window was created

due to electromagnetically induced transparency, and the incident squeezed

vacuum could pass through the cold atoms without optical loss, as was

successfully monitored using a time-domain homodyne method.

\\ ( http://arxiv.org/abs/0707.1971 , 188kb)

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arXiv:0707.2038

Date: Fri, 13 Jul 2007 15:28:11 GMT (77kb)

Title: Self-cooling of a movable mirror to the ground state using radiation

pressure

Authors: Aurelien Dantan (University of Aarhus), Claudiu Genes (Universita Di

Camerino), David Vitali (Universita Di Camerino), Michel Pinard (LKB -

Jussieu)

Categories: quant-ph

Comments: 4 pages, 3 figures

Proxy: ccsd hal-00162568

\\

We show that one can cool a micro-mechanical oscillator to its quantum ground

state using radiation pressure in an appropriately detuned cavity

(self-cooling). From a simple theory based on Heisenberg-Langevin equations we

find that optimal self-cooling occurs in the good cavity regime, when the

cavity bandwidth is smaller than the mechanical frequency, but still larger

than the effective mechanical damping. In this case the intracavity field and

the vibrational mechanical mode coherently exchange their fluctuations. We also

present dynamical calculations which show how to access the mirror final

temperature from the fluctuations of the field reflected by the cavity.

\\ ( http://arxiv.org/abs/0707.2038 , 77kb)

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arXiv:0707.1916

Date: Fri, 13 Jul 2007 03:39:40 GMT (433kb)

Title: Lattice with a Twist : Helical Waveguides for Ultracold Matter

Authors: M. Bhattacharya

Categories: physics.atom-ph physics.optics

Comments: Accepted for publication in Optics Communications

\\

We investigate the waveguiding properties of the optical interference pattern

of two counter-propagating Laguerre-Gaussian beams. The number, helicity,

radius, pitch, depth and frequencies of transverse confinement of the

waveguides are simply related to the beam parameters. Quantitative connections

to the familiar Gaussian optical lattice are made and an application to quantum

transport is suggested.

\\ ( http://arxiv.org/abs/0707.1916 , 433kb)

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arXiv:0707.2015

Date: Fri, 13 Jul 2007 14:11:18 GMT (167kb)

Title: Trapping of ultracold polar molecules with a Thin Wire Electrostatic

Trap

Authors: J. Kleinert, C. Haimberger, P. J. Zabawa, and N. P. Bigelow

Categories: physics.atom-ph

Comments: 4 pages, 3 figures

\\

We describe the realization of a DC electric field trap for ultracold polar

molecules, the Thin WIre electroStatic Trap (TWIST). The thin wires that form

the electrodes of the TWIST allow us to superimpose the trap onto a

magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules

in their electronic ground state are created in the MOT via photoassociation,

achieving a continuous accumulation in the TWIST of molecules in low-field

seeking states. Initial measurements show that the TWIST trap lifetime is

limited only by the background pressure in the chamber.

\\ ( http://arxiv.org/abs/0707.2015 , 167kb)

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arXiv:0707.1910

Date: Fri, 13 Jul 2007 02:51:52 GMT (427kb)

Title: Dispersive, superfluid-like shock waves in nonlinear optics

Authors: Wenjie Wan, Shu Jia, and Jason W. Fleischer

Categories: physics.optics physics.flu-dyn

Comments: 21 pages, 6 figures Revised abstract

Journal-ref: Nature Physics 3, 46 (2007)

\\

In most classical fluids, shock waves are strongly dissipative, their energy

being quickly lost through viscous damping. But in systems such as cold

plasmas, superfluids, and Bose-Einstein condensates, where viscosity is

negligible or non-existent, a fundamentally different type of shock wave can

emerge whose behaviour is dominated by dispersion rather than dissipation.

Dispersive shock waves are difficult to study experimentally, and analytical

solutions to the equations that govern them have only been found in one

dimension (1D). By exploiting a well-known, but little appreciated,

correspondence between the behaviour of superfluids and nonlinear optical

materials, we demonstrate an all-optical experimental platform for studying the

dynamics of dispersive shock waves. This enables us to observe the propagation

and nonlinear response of dispersive shock waves, including the interaction of

colliding shock waves, in 1D and 2D. Our system offers a versatile and more

accessible means for exploring superfluid-like and related dispersive

phenomena.

\\ ( http://arxiv.org/abs/0707.1910 , 427kb)

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arXiv:0707.2084

Date: Fri, 13 Jul 2007 20:02:17 GMT (47kb)

Title: A quantum topological phase transition at the microscopic level

Authors: Claudio Castelnovo (1), and Claudio Chamon (2). ((1) Oxford

University, (2) Boston University)

Categories: cond-mat.str-el

Comments: (13 pages, 4 figures)

\\

We study a quantum phase transition between a phase which is topologically

ordered and one which is not. We focus on a spin model, an extension of the

toric code, for which we obtain the exact ground state for all values of the

coupling constant that takes the system across the phase transition. We compute

the entanglement and the topological entropy of the system as a function of

this coupling constant, and show that the topological entropy remains constant

all the way up to the critical point, and jumps to zero beyond it. Despite the

jump in the topological entropy, the transition is second order as detected via

any local observable.

\\ ( http://arxiv.org/abs/0707.2084 , 47kb)

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arXiv:0707.2109

Date: Fri, 13 Jul 2007 23:21:34 GMT (262kb)

Title: Bose-Einstein condensation in an optical lattice

Authors: P. B. Blakie and Wen-Xin Wang

Categories: cond-mat.other

Comments: 10 pages, 5 figures

\\

In this paper we develop an analytic expression for the critical temperature

for a gas of ideal bosons in a combined harmonic lattice potential, relevant to

current experiments using optical lattices. We give corrections to the critical

temperature arising from effective mass modifications of the low energy

spectrum, finite size effects and excited band states. We compute the critical

temperature using numerical methods and compare to our analytic result. We

study condensation in an optical lattice over a wide parameter regime and

demonstrate that the critical temperature can be increased or reduced relative

to the purely harmonic case by adjusting the harmonic trap frequency. We show

that a simple numerical procedure based on a piecewise analytic density of

states provides an accurate prediction for the critical temperature.

\\ ( http://arxiv.org/abs/0707.2109 , 262kb)

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arXiv:0707.2196

Date: Sun, 15 Jul 2007 10:34:30 GMT (329kb)

Title: The single-particle density matrix and the momentum distribution of dark

"solitons" in a Tonks-Girardeau gas

Authors: H. Buljan, K. Lelas, R. Pezer, and M. Jablan

Categories: cond-mat.other

Comments: 9 pages, 8 figures

\\

We study the reduced single-particle density matrix (RSPDM), the momentum

distribution, natural orbitals and their occupancies, of dark "soliton" (DS)

states in a Tonks-Girardeau gas. DS states are specially tailored excited

many-body eigenstates, which have a dark solitonic notch in their

single-particle density. The momentum distribution of DS states has a

characteristic shape with two sharp spikes. We find that the two spikes arise

due to the high degree of correlation observed within the RSPDM between the

mirror points ($x$ and $-x$) with respect to the dark notch at $x=0$; the

correlations oscillate rather than decay as the points $x$ and $-x$ are being

separated.

\\ ( http://arxiv.org/abs/0707.2196 , 329kb)

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arXiv:0707.2243

Date: Sun, 15 Jul 2007 22:42:56 GMT (81kb)

Title: Dissipative Dynamics of Matter Wave Soliton in Nonlinear Optical Lattice

Authors: F.Kh. Abdullaev, A. Gammal, H.L.F. da Luz, and Lauro Tomio

Categories: cond-mat.other

Comments: 9 pages, 8 figures

\\

Dynamics and stability of solitons in two-dimensional (2D) Bose-Einstein

condensates (BEC), with low-dimensional (1D) conservative plus dissipative

nonlinear optical lattices are investigated. In the case of focusing media

(with attractive atomic systems) the collapse of the wave packet is arrested by

the dissipative periodic nonlinearity. The adiabatic variation of the

background scattering length leads to metastable matter-wave solitons.

When the atom feeding mechanism is used, a dissipative soliton can exist in

focusing 2D media with 1D periodic nonlinearity. In the defocusing media

(repulsive BEC case) with harmonic trap in one dimension and one dimensional

nonlinear optical lattice in other direction, the stable soliton can exist.

This prediction of variational approach is confirmed by the full numerical

simulation of 2D Gross-Pitaevskii equation.

\\ ( http://arxiv.org/abs/0707.2243 , 81kb)

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arXiv:0707.2307

Date: Mon, 16 Jul 2007 12:11:01 GMT (8kb)

Title: A microcanonical quantum fluctuation theorem

Authors: Peter Talkner, Peter Hanggi, Manuel Morillo

Categories: cond-mat.stat-mech

\\

Previously derived expressions for the characteristic function of work

performed on a quantum system by a classical external force are generalized to

arbitrary initial states of the considered system and to Hamiltonians with

degenerate spectra. In the particular case of microcanonical initial states a

fluctuation theorem is derived which relates averages of shifted inverse work

describing an out of equilibrium process to equilibrium entropies of

microcanonical states.

\\ ( http://arxiv.org/abs/0707.2307 , 8kb)

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arXiv:0707.2354

Date: Mon, 16 Jul 2007 16:33:49 GMT (213kb)

Title: Critical velocity for superfluid flow across the BEC-BCS crossover

Authors: D. E. Miller, J. K. Chin, C. A. Stan, Y. Liu, W. Setiawan, C. Sanner

and W. Ketterle

Categories: cond-mat.other

\\

Critical velocities have been observed in an ultracold superfluid Fermi gas

throughout the BEC-BCS crossover. A pronounced peak of the critical velocity at

unitarity demonstrates that superfluidity is most robust for resonant atomic

interactions. Critical velocities were determined from the abrupt onset of

dissipation when the velocity of a moving one dimensional optical lattice was

varied. The dependence of the critical velocity on lattice depth and on the

inhomogeneous density profile was studied.

\\ ( http://arxiv.org/abs/0707.2354 , 213kb)

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arXiv:0707.2359

Date: Mon, 16 Jul 2007 16:52:12 GMT (117kb)

Title: Manufacturing a thin wire electrostatic trap (TWIST) for ultracold polar

molecules

Authors: J. Kleinert, C. Haimberger, P. J. Zabawa, and N. P. Bigelow

Categories: physics.atom-ph

Comments: 3 pages, 2 figures

\\

We present a detailed description on how to build a Thin WIre electroStatic

Trap (TWIST) for ultracold polar molecules which can be superimposed onto a

magneto optical trap. The required parts are easily accessible and inexpensive

(bill of parts $<$\$1000). A machine shop, a protected atmosphere glove box,

and a fume hood are sufficient to manufacture the TWIST.

\\ ( http://arxiv.org/abs/0707.2359 , 117kb)

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arXiv:0707.2178

Date: Sat, 14 Jul 2007 23:04:59 GMT (91kb)

Title: Stimulated radiative laser cooling

Authors: Peter Muys

Categories: physics.optics

\\

Building a refrigerator based on the conversion of heat into optical energy

is an ongoing engineering challenge. Under well-defined conditions, spontaneous

anti-Stokes fluorescence of a dopant material in a host matrix is capable of

lowering the host temperature. The fluorescence is conveying away a part of the

thermal energy stored in the vibrational oscillations of the host lattice. In

particular, applying this principle to the cooling of (solid-state) lasers

opens up many potential device applications, especially in the domain of

high-power lasers. In this paper, an alternative optical cooling scheme is

outlined, leading to radiative cooling of solid-state lasers. It is based on

converting the thermal energy stored in the host, into optical energy by means

of a stimulated nonlinear process, rather than a spontaneous process. This

should lead to better cooling efficiencies and a higher potential of applying

the principle for device applications.

\\ ( http://arxiv.org/abs/0707.2178 , 91kb)

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arXiv:0707.2378

Date: Mon, 16 Jul 2007 20:00:16 GMT (428kb)

Title: Trionic phase of ultracold fermions in an optical lattice: a variational

study

Authors: Akos Rapp, Walter Hofstetter, and Gergely Zarand

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

Comments: 14 PRB pages, 8 figures

\\

To investigate ultracold fermionic atoms of three internal states (colors) in

an optical lattice, subject to strong attractive interaction, we study the

attractive three-color Hubbard model in infinite dimensions using a variational

approach. We find a quantum phase transition between a weak coupling

superconducting phase and a strong coupling trionic phase where groups of three

atoms are bound to a composite fermion. We show how the Gutzwiller variational

theory can be reformulated in terms of an effective field theory with

three-body interactions, and how this effective field theory can be solved

exactly in infinite dimensions using the methods of dynamical mean field

theory.

\\ ( http://arxiv.org/abs/0707.2378 , 428kb)

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arXiv:0707.2383

Date: Mon, 16 Jul 2007 20:16:41 GMT (152kb)

Title: Superfluid-insulator transitions of the Fermi gas with near-unitary

interactions in a periodic potential

Authors: Eun Gook Moon, Predrag Nikolic, and Subir Sachdev

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

Comments: 5 pages, 3 figures

\\

We consider spin-1/2 fermions of mass m with interactions near the unitary

limit. In an applied periodic potential of amplitude V and period a, and with a

density of an even integer number of fermions per unit cell, there is a

second-order quantum phase transition between superfluid and insulating ground

states at a critical V=Vc. We compute the universal ratio Vc m a^2 / h^2 at

N=infinity in a model with Sp(2N) spin symmetry. The insulator interpolates

between a band insulator of fermions and a Mott insulator of fermion pairs. We

discuss implications for recent experiments.

\\ ( http://arxiv.org/abs/0707.2383 , 152kb)

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arXiv:0707.2422

Date: Tue, 17 Jul 2007 02:54:30 GMT (286kb)

Title: Excitation spectrum of bosons in a finite one-dimensional circular

waveguide via the Bethe ansatz

Authors: Andrew G. Sykes, Peter D. Drummond and Matthew J. Davis

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

Comments: 13 pages, 12 figures

\\

The exactly solvable Lieb-Liniger model of interacting bosons in

one-dimension has attracted renewed interest as current experiments with

ultra-cold atoms begin to probe this regime. Here we numerically solve the

equations arising from the Bethe ansatz solution for the exact many-body wave

function in a finite-size system of up to twenty particles for attractive

interactions. We discuss the novel features of the solutions, and how they

deviate from the well-known string solutions [H. B. Thacker, Rev. Mod. Phys.\

\textbf{53}, 253 (1981)] at finite densities. We present excited state string

solutions in the limit of strong interactions and discuss their physical

interpretation, as well as the characteristics of the quantum phase transition

that occurs as a function of interaction strength in the mean-field limit.

Finally we compare our results to those of exact diagonalization of the

many-body Hamiltonian in a truncated basis. We also present excited state

solutions and the excitation spectrum for the repulsive 1D Bose gas on a ring.

\\ ( http://arxiv.org/abs/0707.2422 , 286kb)

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arXiv:0707.2435

Date: Tue, 17 Jul 2007 05:16:43 GMT (124kb)

Title: Effective mean-field equations for cigar-shaped and disk-shaped

Bose-Einstein condensates

Authors: A. Mu\~noz Mateo and V. Delgado (Univ. de La Laguna)

Categories: cond-mat.other

Comments: 10 pages, 8 figures

\\

By applying the standard adiabatic approximation and using the accurate

analytical expression for the corresponding local chemical potential obtained

in our previous work [Phys. Rev. A \textbf{75}, 063610 (2007)] we derive an

effective 1D equation that governs the axial dynamics of mean-field

cigar-shaped condensates with repulsive interatomic interactions, accounting

accurately for the contribution from the transverse degrees of freedom. This

equation, which is more simple than previous proposals, is also more accurate.

Moreover, it allows treating condensates containing an axisymmetric vortex with

no additional cost. Our effective equation also has the correct limit in both

the quasi-1D mean-field regime and the Thomas-Fermi regime and permits one to

derive fully analytical expressions for ground-state properties such as the

chemical potential, axial length, axial density profile, and local sound

velocity. These analytical expressions remain valid and accurate in between the

above two extreme regimes. Following the same procedure we also derive an

effective 2D equation that governs the transverse dynamics of mean-field

disk-shaped condensates. This equation, which also has the correct limit in

both the quasi-2D and the Thomas-Fermi regime, is again more simple and

accurate than previous proposals. We have checked the validity of our equations

by numerically solving the full 3D Gross-Pitaevskii equation.

\\ ( http://arxiv.org/abs/0707.2435 , 124kb)

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arXiv:0707.2512

Date: Tue, 17 Jul 2007 13:17:38 GMT (484kb)

Title: Generalized Neighbor-Interaction Models Induced by Nonlinear Lattices

Authors: F. Kh. Abdullaev, Yu. V. Bludov, S. V. Dmitriev, P. G. Kevrekidis, V.

V. Konotop

Categories: cond-mat.other

\\

It is shown that the tight-binding approximation of the nonlinear

Schr\"odinger equation with a periodic linear potential and periodic in space

nonlinearity coefficient gives rise to a number of nonlinear lattices with

complex, both linear and nonlinear, neighbor interactions. The obtained

lattices present non-standard possibilities, among which we mention a

quasi-linear regime, where the pulse dynamics obeys essentially the linear

Schr{\"o}dinger equation. We analyze the properties of such models both in

connection with their modulational stability, as well as in regard to the

existence and stability of their localized solitary wave solutions.

\\ ( http://arxiv.org/abs/0707.2512 , 484kb)

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arXiv:0707.2571

Date: Tue, 17 Jul 2007 17:15:47 GMT (496kb)

Title: Dynamical and energetic instabilities in multi-component Bose-Einstein

condensates in optical lattices

Authors: J. Ruostekoski and Zachary Dutton

Categories: cond-mat.other

Comments: 17 pages, 12 figures. Submitted to Phys. Rev. A

\\

We study dynamical and energetic instabilities in the transport properties of

Bloch waves for atomic multi-component Bose-Einstein condensates in optical

lattices in the tight-binding limit. We obtain stability criteria analytically,

as a function of superfluid velocities and interaction parameters, in several

cases for two-component and spinor condensates. In the two-species case we find

that the presence of the other condensate component can stabilize the

superfluid flow of an otherwise unstable condensate and that the free space

dynamical miscibility condition of the two species can be reversed by tuning

the superfluid flow velocities. In spin-1 condensates, we find the steady-state

Bloch wave solutions and characterize their stability criteria. We find

generally more regions of dynamical instability arise for the polar than for

the ferromagnetic solutions. In the presence of magnetic Zeeman shifts, we find

a richer variety of condensate solutions and find that the linear Zeeman shift

can stabilize the superfluid flow in several cases of interest.

\\ ( http://arxiv.org/abs/0707.2571 , 496kb)

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arXiv:0707.2574

Date: Tue, 17 Jul 2007 17:23:03 GMT (361kb)

Title: Is a gas of strongly interacting atomic fermions a nearly perfect fluid?

Authors: A. Turlapov, J. Kinast, B. Clancy, Le Luo, J. Joseph and J. E. Thomas

Categories: cond-mat.other

Comments: 10 pages, 5 figures

\\

We use all-optical methods to produce a highly-degenerate Fermi gas of

spin-1/2 $^6$Li atoms. A magnetic field tunes the gas near a collisional

(Feshbach) resonance, producing strong interactions between spin-up and

spin-down atoms. This atomic gas is a paradigm for strong interactions in

nature, and provides tests of current quantum many-body calculational methods

for diverse systems, including very high temperature superconductors, nuclear

matter in neutron stars, and the quark-gluon plasma of the Big Bang. We have

measured properties of a breathing mode over a wide range of temperatures. At

temperatures both below and well above the superfluid transition, the frequency

of the mode is nearly constant and very close to the hydrodynamic value.

However, explaining both the frequency and the damping rate in the normal

collisional regime has not been achieved. Our measurements of the damping rate

as a function of the energy of the gas are used to estimate an upper bound on

the viscosity. Using our new measurements of the entropy of the gas, we

estimate the ratio of the shear viscosity to the entropy density, and compare

the result with the lower bound for quantum viscosity recently predicted using

string theory methods.

\\ ( http://arxiv.org/abs/0707.2574 , 361kb)

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arXiv:0707.2398

Date: Mon, 16 Jul 2007 21:31:44 GMT (24kb)

Title: Production of mesoscopic superpositions with ultracold atoms

Authors: H. T. Ng

Categories: quant-ph

Comments: 4 pages, 2 figures

\\

We study mesoscopic superpositions of two component Bose-Einstein

condensates. Atomic condensates, with long coherence times, are good systems in

which to study such quantum phenomenon. We show that the mesoscopic

superposition states can be rapidly generated in which the atoms dispersively

interact with the photon field in a cavity. We also discuss the production of

compass states which are generalized Schr\"{o}dinger cat states. The physical

realization of mesoscopic states is important in studying decoherence and

precision measurement.

\\ ( http://arxiv.org/abs/0707.2398 , 24kb)

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arXiv:0707.2401

Date: Tue, 17 Jul 2007 13:56:52 GMT (167kb)

Title: Enhancement of the formation of ultracold $^{85}$Rb$_2$ molecules due to

resonant coupling

Authors: H. K. Pechkis, D. Wang, Y. Huang, E. E. Eyler, P. L. Gould, W. C.

Stwalley, and C. P. Koch

Categories: physics.atom-ph

Comments: 6 pages, 5 figures; corrected author list

\\

We have studied the effect of resonant electronic state coupling on the

formation of ultracold ground-state $^{85}$Rb$_2$. Ultracold Rb$_2$ molecules

are formed by photoassociation (PA) to a coupled pair of $0_u^+$ states,

$0_u^+(P_{1/2})$ and $0_u^+(P_{3/2})$, in the region below the $5S+5P_{1/2}$

limit. Subsequent radiative decay produces high vibrational levels of the

ground state, $X ^1\Sigma_g^+$. The population distribution of these $X$ state

vibrational levels is monitored by resonance-enhanced two-photon ionization

through the $2 ^1\Sigma_u^+$ state. We find that the populations of vibrational

levels $v''$=112$-$116 are far larger than can be accounted for by the

Franck-Condon factors for $0_u^+(P_{1/2}) \to X ^1\Sigma_g^+$ transitions with

the $0_u^+(P_{1/2})$ state treated as a single channel. Further, the

ground-state molecule population exhibits oscillatory behavior as the PA laser

is tuned through a succession of $0_u^+$ state vibrational levels. Both of

these effects are explained by a new calculation of transition amplitudes that

includes the resonant character of the spin-orbit coupling of the two $0_u^+$

states. The resulting enhancement of more deeply bound ground-state molecule

formation will be useful for future experiments on ultracold molecules.

\\ ( http://arxiv.org/abs/0707.2401 , 167kb)

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\\

arXiv:0707.2625

Date: Wed, 18 Jul 2007 03:09:49 GMT (34kb)

Title: Radio Frequency Spectroscopy of Trapped Fermi Gases with Population

Imbalance

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

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

Comments: 4 page, 3 figures, submitted to PRA Rapid

\\

We address radio frequency (RF) spectroscopy experiments on population

imbalanced Fermi gases, which show satisfactory agreement between theory and

experiment for the moderately polarized gases. At high imbalance, experiments

report a paired but normal state at very high and very low T, for both of which

we find no natural theoretical explanation. Given the importance of these

experimental claims, we present a series of related theoretical RF

spectroscopic calculations. By comparison with present and future experiments,

these may help to rule out different scenarios for this strange phase.

\\ ( http://arxiv.org/abs/0707.2625 , 34kb)

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\\

arXiv:0707.2715

Date: Wed, 18 Jul 2007 12:43:57 GMT (303kb)

Title: Condensation of Ideal Bose Gas Confined in a Box within Canonical

Ensemble

Authors: Konstantin Glaum, Hagen Kleinert, Axel Pelster

Categories: cond-mat.stat-mech

Comments: 18 pages, 8 figures

\\

We set up recursion relations for the partition function and the ground-state

occupancy for a fixed number of non-interacting bosons confined in a square box

potential and determine the temperature dependence of the specific heat and the

particle number in the ground state. A proper semiclassical treatment is set up

which yields the correct small-T-behavior in contrast to an earlier theory in

Feynman's textbook on Statistical Mechanics, in which the special role of the

ground state was ignored. The results are compared with an exact quantum

mechanical treatment. Furthermore, we derive the finite-size effect of the

system.

\\ ( http://arxiv.org/abs/0707.2715 , 303kb)

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\\

arXiv:0707.2861

Date: Thu, 19 Jul 2007 09:38:20 GMT (39kb)

Title: Soliton oscillations in collisionally inhomogeneous attractive

Bose-Einstein condensates

Authors: P. Niarchou, G. Theocharis, P.G. Kevrekidis, P. Schmelcher, and D.J.

Frantzeskakis

Categories: cond-mat.other

\\

We investigate bright matter-wave solitons in the presence of a spatially

varying nonlinearity. It is demonstrated that a translation mode is excited due

to the spatial inhomogeneity and its frequency is derived analytically and also

studied numerically. Both cases of purely one-dimensional and ``cigar-shaped''

condensates are studied by means of different mean-field models, and the

oscillation frequencies of the pertinent solitons are found and compared with

the results obtained by the linear stability analysis.Numerical results are

shown to be in very good agreement with the corresponding analytical

predictions.

\\ ( http://arxiv.org/abs/0707.2861 , 39kb)

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\\

arXiv:0707.2918

Date: Thu, 19 Jul 2007 14:58:57 GMT (414kb)

Title: Localization of Bogolyubov Quasiparticles in Interacting Bose-Einstein

Condensates Subjected to Correlated Random Potentials

Authors: Pierre Lugan (LCFIO), David Cl\'ement (LCFIO), Philippe Bouyer

(LCFIO), Alain Aspect (LCFIO), Laurent Sanchez-Palencia (LCFIO)

Categories: cond-mat.other

Comments: 4 pages, 2 figures

Proxy: ccsd hal-00163902

\\

We study the Anderson localization of Bogolyubov quasiparticles in an

interacting Bose-Einstein condensate (with healing length \xi) subjected to a

random potential (with finite correlation length \sigma_R). We derive

analytically the Lyapunov exponent as a function of the quasiparticle momentum

k and we study the localization maximum k_{max}. For 1D speckle potentials, we

find that k_{max} is proportional to 1/\xi when \xi is much larger than

\sigma_R while k_{max} is proportional to 1/\sigma_R when \xi is much smaller

than \sigma_R, and that the localization is strongest when \xi is of the order

of \sigma_R. Numerical calculations support our analysis and our estimates

indicate that the localization of the Bogolyubov quasiparticles is accessible

in current experiments with ultracold atoms.

\\ ( http://arxiv.org/abs/0707.2918 , 414kb)

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\\

arXiv:0707.2937

Date: Thu, 19 Jul 2007 16:40:46 GMT (61kb)

Title: Excitation Spectra of Correlated Lattice Bosons in a Confining Trap

Authors: Dmitry L. Kovrizhin (Clarendon Laboratory, University of Oxford) G.

Venketeswara Pai (Technion) Subhasis Sinha (S.N. Bose National Centre for

Basic Sciences)

Categories: cond-mat.stat-mech

Comments: 4 pages, 3 figures

\\

We consider ultracold bosonic atoms in an optical lattice with an external

trapping potential. To study the excitation energies of the resulting

Bose-Hubbard model, we develop a method based on a time-dependent

generalization of the Gutzwiller ansatz. We calculate the excitations of the

homogeneous system both in insulating and superfluid regime, concentrating

particularly on those near the superfluid-Mott insulator boundary. Low-lying

excitation energies in presence of a static harmonic trap are obtained using

this method and compared with the homogeneous case. Further, we explore the

dynamics of the center of mass and the breathing mode in response to

time-dependent perturbations of the trap.

\\ ( http://arxiv.org/abs/0707.2937 , 61kb)

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\\

arXiv:0707.2665 (*cross-listing*)

Date: Wed, 18 Jul 2007 08:04:13 GMT (13kb)

Title: Hydrodynamic fluctuations in relativistic superfluids

Authors: Manuel A. Valle

Categories: hep-ph cond-mat.other

Comments: 12 pages, no figures

\\

The Hamiltonian formulation of superfluids based on noncanonical Poisson

brackets is studied in detail. The assumption that the momentum density is

proportional to the flow of the conserved energy is shown to lead to the

covariant relativistic theory previously suggested by Khalatnikov and Lebedev,

and some potentials in this theory are given explicitly. We discuss

hydrodynamic fluctuations in the presence of dissipative effects and we derive

the corresponding set of hydrodynamic correlation functions. Kubo relations for

the transport coefficients are obtained.

\\ ( http://arxiv.org/abs/0707.2665 , 13kb)

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\\

arXiv:0707.2930

Date: Thu, 19 Jul 2007 16:07:45 GMT (598kb)

Title: Strong saturation absorption imaging of dense clouds of ultracold atoms

Authors: G. Reinaudi, T. Lahaye, Z. Wang, and D. Guery-Odelin

Categories: physics.optics physics.atom-ph

Comments: 3 pages, 2 figures

\\

We report on a far above saturation absorption imaging technique to

investigate the characteristics of dense packets of ultracold atoms. The

transparency of the cloud is controlled by the incident light intensity as a

result of the non-linear response of the atoms to the probe beam. We detail our

experimental procedure to calibrate the imaging system for reliable

quantitative measurements, and demonstrate the use of this technique to extract

the profile and its spatial extent of an optically thick atomic cloud.

\\ ( http://arxiv.org/abs/0707.2930 , 598kb)

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Replacements:

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\\

arXiv:cond-mat/0703282

replaced with revised version Fri, 13 Jul 2007 06:30:53 GMT (7kb)

Title: A practical method to estimate the condensate fraction of interacting

and trapped Bose atoms

Authors: Sang-Hoon Kim

Categories: cond-mat.stat-mech

Comments: 2 pages, 2 figures

-----------------------------------------------------------------------------

\\

arXiv:0704.1889

replaced with revised version Mon, 16 Jul 2007 07:25:49 GMT (40kb)

Title: First and second sound modes at finite temperature in trapped Fermi

gases from BCS to BEC

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

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

Comments: 4 pages, 3 figures, replaced with revised version

\\ ( http://arxiv.org/abs/0704.1889 , 40kb)

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\\

arXiv:cond-mat/0611379

replaced with revised version Mon, 16 Jul 2007 13:07:18 GMT (35kb)

Title: Predicting spinor condensate dynamics from simple principles

Authors: M. Moreno-Cardoner, J. Mur-Petit, M. Guilleumas, A. Polls, A. Sanpera,

and M. Lewenstein

Categories: cond-mat.mes-hall

Comments: 4 pages, 2 figures. v3: matches version appeared in PRL

Journal-ref: Phys. Rev. Lett. 99, 020404 (2007)

DOI: 10.1103/PhysRevLett.99.020404

\\ ( http://arxiv.org/abs/cond-mat/0611379 , 35kb)

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\\

arXiv:cond-mat/0703454

replaced with revised version Sun, 15 Jul 2007 00:03:56 GMT (269kb)

Title: Simulation and detection of Dirac fermions with cold atoms in an optical

lattice

Authors: Shi-Liang Zhu, Baigeng Wang, and L.-M. Duan

Categories: cond-mat.mtrl-sci

Comments: 4 pages; Published version

Journal-ref: Phys. Rev. Lett 98, 260402 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0703454 , 269kb)

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\\

arXiv:cond-mat/0703523

replaced with revised version Mon, 16 Jul 2007 15:48:35 GMT (8kb)

Title: Vortex mass in a superfluid at low frequencies

Authors: D. J. Thouless and J. R. Anglin

Categories: cond-mat.other

Comments: 4 pages

\\ ( http://arxiv.org/abs/cond-mat/0703523 , 8kb)

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\\

arXiv:quant-ph/0703185

replaced with revised version Sat, 14 Jul 2007 12:45:35 GMT (309kb)

Title: Addressing individual atoms in optical lattices with standing-wave

driving fields

Authors: Jaeyoon Cho

Categories: quant-ph

Comments: 4 pages, 3 figures; minor revisions

Journal-ref: Phys. Rev. Lett. 99, 020502 (2007)

\\ ( http://arxiv.org/abs/quant-ph/0703185 , 309kb)

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\\

arXiv:physics/0608083

replaced with revised version Sat, 14 Jul 2007 02:57:22 GMT (435kb)

Title: Demonstration of a moving guide based atom interferometer for rotation

sensing

Authors: Saijun Wu, Edward J. Su, Mara Prentiss

Categories: physics.atom-ph physics.optics

Comments: 4 pages, 4 figures (Major revision with new figures)

\\ ( http://arxiv.org/abs/physics/0608083 , 435kb)

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\\

arXiv:0705.2499

replaced with revised version Tue, 17 Jul 2007 08:23:17 GMT (16kb)

Title: Nonclassical rotational inertia for a supersolid under rotation

Authors: Amandine Aftalion, Xavier Blanc, Robert L. Jerrard

Categories: cond-mat.other

\\ ( http://arxiv.org/abs/0705.2499 , 16kb)

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\\

arXiv:cond-mat/0512317

replaced with revised version Wed, 18 Jul 2007 17:53:46 GMT (33kb)

Title: The axial breathing mode in rapidly rotating Bose-Einstein condensates

and uncertainty of the rotation velocity

Authors: Gentaro Watanabe

Categories: cond-mat.mes-hall cond-mat.soft nucl-th

Comments: 5 pages, 2 figures; this paper is related to cond-mat/0506331;

accepted for publication in Phys. Rev. A Rapid Communications

Report-no: NORDITA-2005-80

\\ ( http://arxiv.org/abs/cond-mat/0512317 , 33kb)

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\\

arXiv:0705.2518

replaced with revised version Wed, 18 Jul 2007 18:30:13 GMT (144kb)

Title: Spectroscopy of Strong-Pulse Superradiance in a Bose-Einstein condensate

Authors: Nir Bar-Gill, Eitan E. Rowen and Nir Davidson

Categories: cond-mat.other

\\ ( http://arxiv.org/abs/0705.2518 , 144kb)

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\\

arXiv:quant-ph/0602081

replaced with revised version Wed, 18 Jul 2007 02:42:42 GMT (186kb)

Title: Short-time quantum correlations in the atom optics kicked rotor

Authors: S.A. Wayper, W. Simpson and M.D. Hoogerland

Categories: quant-ph

Comments: 6 pages, 4 figures

\\ ( http://arxiv.org/abs/quant-ph/0602081 , 186kb)

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\\

arXiv:cond-mat/0701464

replaced with revised version Thu, 19 Jul 2007 10:06:46 GMT (69kb)

Title: Trapped fermionic clouds distorted from the trap shape due to many-body

effects

Authors: Masudul Haque, H.T.C. Stoof

Categories: cond-mat.mes-hall cond-mat.supr-con

Comments: 4+ pages, 3 figures. Formalism for distorted trapped fermi systems +

treatment of polarized fermion experiments. Version 2: slightly shortened,

published version

Journal-ref: Physical Review Letters, 98, 260406 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0701464 , 69kb)

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\\

arXiv:quant-ph/0703065

replaced with revised version Thu, 19 Jul 2007 16:08:19 GMT (823kb)

Title: Cavity-enhanced superradiant Rayleigh scattering with ultra-cold and

Bose-Einstein condensed atoms

Authors: Sebastian Slama, Gordon Krenz, Simone Bux, Claus Zimmermann, and

Philippe W. Courteille

Categories: quant-ph

Comments: 10 pages, 10 figures

Journal-ref: Physical Review A 75, 063620 (2007)

DOI: 10.1103/PhysRevA.75.063620

\\ ( http://arxiv.org/abs/quant-ph/0703065 , 823kb)

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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 Tue Jul 31 2007 - 15:50:52 EST

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