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

Date: Mon, 14 May 2007 09:54:15 +1000 (EST)

Date: Mon, 14 May 2007 09:54:15 +1000 (EST)

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

Hi all,

I think I've broken my previous record for the lateness of a week's mailing.

Thankfully by the time you finish reading this the following two weeks emails

will be sitting in your inbox ready to be enjoyed, and once again you will be

entirely up to date.

I've gone through so many papers in this scanning session that I can't even

remember the interesting ones. I'll have to revisit them again later. There are

28 new preprints and 14 replacements this week.

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arXiv:0704.2623

Date: Thu, 19 Apr 2007 22:11:20 GMT (413kb)

Title: Bragg spectroscopy of a superfluid Bose-Hubbard gas

Authors: X. Du, Shoupu Wan, Emek Yesilada, C. Ryu, D. J. Heinzen, Z. X. Liang,

and Biao Wu

Categories: cond-mat.other

Comments: 11 pages, 4 figures

\\

Bragg spectroscopy is used to measure excitations of a trapped,

quantum-degenerate gas of 87Rb atoms in a 3-dimensional optical lattice. The

measurements are carried out over a range of optical lattice depths in the

superfluid phase of the Bose-Hubbard model. For fixed wavevector, the resonant

frequency of the excitation is found to decrease with increasing lattice depth.

A numerical calculation of the resonant frequencies based on Bogoliubov theory

shows a less steep rate of decrease than the measurements.

\\ ( http://arxiv.org/abs/0704.2623 , 413kb)

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arXiv:0704.2660

Date: Fri, 20 Apr 2007 07:10:25 GMT (54kb)

Title: Competing superfluid and density-wave ground-states of fermionic

mixtures with mass imbalance in optical lattices

Authors: Tung-Lam Dao, Antoine Georges, Massimo Capone.

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

Comments: e.g.:4 pages, 3 figures

\\

We study the effect of mass imbalance on the phase diagram of a two-component

fermionic mixture with attractive interactions in optical lattices. Using

static and dynamical mean-field theories, we show that the pure superfluid

phase is stable for all couplings when the mass imbalance is smaller than a

limiting value. For larger imbalance, phase separation between a superfluid and

a charge-density wave takes place when the coupling exceeds a critical

strength. The harmonic trap induces a spatial segregation of the two phases,

with a rapid variation of the density at the boundary.

\\ ( http://arxiv.org/abs/0704.2660 , 54kb)

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arXiv:0704.2721

Date: Fri, 20 Apr 2007 14:45:33 GMT (211kb)

Title: Half-vortices in polariton condensates

Authors: Yuri Rubo

Categories: cond-mat.other

Comments: 4 pages, 3 figures

\\

It is shown that vortices in linearly polarized polariton condensates in

planar semiconductor microcavities carry two winding numbers (k,m). These

numbers can be either integer or half-integer simultaneously. Four half-integer

vortices (1/2,1/2), (-1/2,-1/2), (1/2,-1/2), and (-1/2,1/2) are anisotropic,

possess the smallest energy, and define the Kosterlitz-Thouless transition

temperature. The condensate concentration remains finite within the core of

half-vortex and the polarization becomes fully circular in the core center.

\\ ( http://arxiv.org/abs/0704.2721 , 211kb)

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arXiv:0704.2648

Date: Fri, 20 Apr 2007 02:31:21 GMT (19kb)

Title: Prospects for making polar molecules with microwave fields

Authors: Svetlana Kotochigova

Categories: quant-ph

Comments: 4 pages, 5 figures

\\

We propose a new mechanism to produce ultracold polar molecules with

microwave fields. The proposed mechanism converts trapped ultracold atoms of

different species into vibrationally excited molecules by a single microwave

transition and entirely depends on the existence of a permanent dipole moment

in the molecules. As opposed to production of molecules by photoassociation or

magnetic-field Feshbach resonances our method does not rely on the structure

and lifetime of excited states or existence of Feshbach resonances. In

addition, we determine conditions for optimal creation of polar molecules in

vibrationally excited states of the ground-state potential by changing

frequency and intensity of the microwave field. We also explore the possibility

to produce vibrationally cold molecules by combining the microwave field with

an optical Raman transition or by applying a microwave field to Feshbach

molecules. The production mechanism is illustrated for two polar molecules: KRb

and RbCs.

\\ ( http://arxiv.org/abs/0704.2648 , 19kb)

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arXiv:0704.2757

Date: Fri, 20 Apr 2007 17:16:45 GMT (259kb)

Title: Polaron Physics in Optical Lattices

Authors: Martin Bruderer, Alexander Klein, Stephen R. Clark, and Dieter Jaksch

Categories: quant-ph

Comments: 5 pages, 4 figures

\\

We investigate the effects of a nearly-uniform Bose-Einstein condensate (BEC)

on the properties of immersed trapped impurity atoms. Using a weak-coupling

expansion in the BEC-impurity interaction strength we derive a model describing

polarons, i.e. impurities dressed by a coherent state of Bogoliubov phonons,

and apply it to ultra-cold bosonic atoms in an optical lattice. We show that

with increasing BEC temperature the transport properties of the impurities

change from coherent to diffusive. Furthermore, stable polaron clusters are

formed via a phonon-mediated off-site attraction.

\\ ( http://arxiv.org/abs/0704.2757 , 259kb)

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arXiv:0704.2627

Date: Thu, 19 Apr 2007 22:31:10 GMT (228kb)

Title: Atom-wave diffraction between the Raman-Nath and the Bragg regime:

Effective Rabi frequency, losses, and phase shifts

Authors: Holger Mueller, Sheng-wey Chiow, and Steven Chu

Categories: physics.atom-ph

Comments: 21 pages, 10 figures

\\

We present an analytic theory of the diffraction of (matter) waves by a

lattice in the "quasi-Bragg" or "channelling" regime between the Bragg and the

short-interaction Raman-Nath regime. The Schroedinger equation is solved by

adiabatic expansion, using the conventional adiabatic approximation as a

starting point, and re-inserting the result into the Schroedinger equation to

yield a second order correction. Closed expressions for arbitrary pulse shapes

and diffraction orders are obtained and the losses of the population to output

states otherwise forbidden by the Bragg condition are derived. We consider the

phase shift due to couplings of the desired output to these states that depends

on the interaction strength and duration and show how these can be kept

negligible by a choice of smooth (e.g., Gaussian) envelope functions even in

situations that substantially violate the adiabaticity condition. We also give

an efficient method for calculating the effective Rabi frequency (which is

related to the eigenvalues of Mathieu functions) in the quasi-Bragg regime.

\\ ( http://arxiv.org/abs/0704.2627 , 228kb)

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arXiv:0704.2856

Date: Sun, 22 Apr 2007 00:21:54 GMT (421kb,D)

Title: State preparation and dynamics of ultracold atoms in higher lattice

orbitals

Authors: Torben Mueller, Simon Foelling, Artur Widera, Immanuel Bloch

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

Comments: 4 pages, 4 figures

\\

We report on the realization of a multi-orbital system with ultracold atoms

in the excited bands of a 3D optical lattice by selectively controlling the

band population along a given lattice direction. The lifetime of the atoms in

the excited band is found to be considerably longer (10-100 times) than the

characteristic time scale for inter-site tunneling, thus opening the path for

orbital selective many-body physics with ultracold atoms. Upon exciting the

atoms from an initial lowest band Mott insulating state to higher lying bands,

we observe the dynamical emergence of coherence in 1D (and 2D), compatible with

Bose-Einstein condensation to a non-zero momentum state.

\\ ( http://arxiv.org/abs/0704.2856 , 421kb)

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arXiv:0704.2957

Date: Mon, 23 Apr 2007 09:29:01 GMT (434kb)

Title: Superfluid-Insulator Transition of Strongly Interacting Fermi Gases in

Optical Lattices

Authors: Hui Zhai and Tin-Lun Ho

Categories: cond-mat.supr-con

Comments: 4 pages, 4 figures

\\

We study a quantum phase transition from fermionic suerpfluid (SF) to

band-insulator (BI) of fermions in optical lattices. The destruction of the

band insulator is driven by the energy gain in promoting fermions in valance

band to various conducting bands to form Cooper pairs. We have obtained the

phase boundary of this transition for systems with two fermions per site using

mean-field theory, which is accurate at fermion side of a Feshbach resonance,

and should give qualitative correct results near resonance. As one moves across

resonance to the molecule side, the SF-BI transition evolves into the SF-Mott

insulator transition of bosonic molecules. The physics becomes more intriguing

at higher fermion densities, and we shall present a qualitative global phase

diagram for SF-Insulator transition for the entire BCS-BEC family. Our results

are directly related to the recent MIT experiment on lattices fermions.

\\ ( http://arxiv.org/abs/0704.2957 , 434kb)

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arXiv:0704.3011

Date: Sun, 22 Apr 2007 23:06:35 GMT (4810kb)

Title: Many-Body Physics with Ultracold Gases

Authors: Immanuel Bloch, Jean Dalibard, Wilhelm Zwerger

Categories: cond-mat.other

Comments: Article for Review of Modern Physics, 76 pages

\\

This article reviews recent experimental and theoretical progress on

many-body phenomena in dilute, ultracold gases. Its focus are effects beyond

standard weak-coupling descriptions, like the Mott-Hubbard-transition in

optical lattices, strongly interacting gases in one dimension or quasi

two-dimensional gases in fast rotation. Strong correlations in fermionic gases

are discussed in optical lattices or near Feshbach resonances in the BCS-BEC

crossover.

\\ ( http://arxiv.org/abs/0704.3011 , 4810kb)

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arXiv:0704.2932

Date: Mon, 23 Apr 2007 07:16:20 GMT (274kb)

Title: Controlling statistical properties of stored light

Authors: A. Raczynski, K. Slowik, J. Zaremba, S. Zielinska-Kaniasty

Categories: quant-ph

Comments: 5 figures

\\

Statistical properties of outgoing light pulses are studies after they have

been stored in a medium of atoms in the tripod configuration. A generalized

Hong-Ou-Mandel interference, storing of squeezed states and homodyne signal

analysis are discussed in the context of their dependence on the parameters of

the control fields used for light storage and release.

\\ ( http://arxiv.org/abs/0704.2932 , 274kb)

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arXiv:0704.2935

Date: Mon, 23 Apr 2007 07:42:39 GMT (397kb)

Title: Formation of Ultracold Heteronuclear Dimers in Electric Fields

Authors: Rosario Gonz\'alez-F\'erez, Michael Mayle and Peter Schmelcher

Categories: quant-ph

\\

The formation of ultracold molecules via stimulated emission followed by a

radiative deexcitation cascade in the presence of a static electric field is

investigated. By analyzing the corresponding cross sections, we demonstrate the

possibility to populate the lowest rotational excitations via photoassociation.

The modification of the radiative cascade due to the electric field leads to

narrow rotational state distributions in the vibrational ground state. External

fields might therefore represent an additional valuable tool towards the

ultimate goal of quantum state preparation of molecules.

\\ ( http://arxiv.org/abs/0704.2935 , 397kb)

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arXiv:0704.3047

Date: Mon, 23 Apr 2007 19:31:05 GMT (437kb)

Title: Atom-atom correlations in spontaneous four wave mixing of two colliding

Bose-Einstein Condensates

Authors: A. Perrin (LCFIO), H. Chang (LCFIO), V. Krachmalnicoff (LCFIO), M.

Schellekens (LCFIO), D. Boiron (LCFIO), A. Aspect (LCFIO), C. I. Westbrook

(LCFIO)

Categories: quant-ph

Proxy: ccsd hal-00142991

\\

We have used a position sensitive, single atom detector to observe atom

scattering during the collision of two Bose-Einstein condensates. The process

can also be thought of as spontaneous, degenerate four wave mixing of deBroglie

waves. The observed two-particle correlation function shows a clear peak

corresponding to the production of back to back atom pairs. The correlation

function also exhibits a peak corresponding to pairs of atoms emitted in the

same direction, the Hanbury Brown-Twiss effect. Our experiment is in the regime

of well separated atom pairs, opening the route to the study of quantum atom

optics effects with individual entangled pairs.

\\ ( http://arxiv.org/abs/0704.3047 , 437kb)

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arXiv:0704.3010

Date: Mon, 23 Apr 2007 14:05:19 GMT (233kb)

Title: Ground-state magneto-optical resonances in Cesium vapour confined in an

extremely thin cell

Authors: C. Andreeva, A. Atvars, M. Auzinsh, K.Bluss, S. Cartaleva, L. Petrov,

and D. Slavov

Categories: physics.atom-ph

\\

Experimental and theoretical studies are presented related to the

ground-state magneto-optical resonance prepared in Cesium vapour confined in an

Extremely Thin Cell (ETC, with thickness equal to the wavelength of the

irradiating light). It is shown that the utilization of the ETC allows one to

examine the formation of a magneto-optical resonance on the individual

hyperfine transitions, thus distinguishing processes resulting in dark (reduced

absorption) or bright (enhanced absorption) resonance formation. We report on

an experimental evidence of the bright magneto-optical resonance sign reversal

in Cs atoms confined in the ETC. A theoretical model is proposed based on the

optical Bloch equations that involves the elastic interaction processes of

atoms in the ETC with its walls resulting in depolarization of the Cs excited

state which is polarized by the exciting radiation. This depolarization leads

to the sign reversal of the bright resonance. Using the proposed model, the

magneto-optical resonance amplitude and width as a function of laser power are

calculated and compared with the experimental ones. The numerical results are

in good agreement with the experiment.

\\ ( http://arxiv.org/abs/0704.3010 , 233kb)

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arXiv:0704.3114

Date: Tue, 24 Apr 2007 18:32:09 GMT (606kb)

Title: Topological Winding and Unwinding in Metastable Bose-Einstein

Condensates

Authors: Rina Kanamoto, Lincoln D. Carr, Masahito Ueda

Categories: cond-mat.other

Comments: 4 pages, 4 figures,

\\

Topological winding and unwinding in a quasi-one-dimensional metastable

Bose-Einstein condensate are shown to be manipulated by changing the strength

of interaction or the frequency of rotation. Exact diagonalization analysis

reveals that quasidegenerate states emerge spontaneously near the transition

point, allowing a smooth crossover between topologically distinct states. On a

mean-field level, the transition is accompanied by formation of grey solitons,

or density notches, which serve as an experimental signature of this

phenomenon.

\\ ( http://arxiv.org/abs/0704.3114 , 606kb)

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arXiv:0704.3116

Date: Tue, 24 Apr 2007 04:46:59 GMT (88kb)

Title: Combinatorics and Boson normal ordering: A gentle introduction

Authors: P. Blasiak (1), A. Horzela (1), K. A. Penson (2), A. I. Solomon (2),

G. H. E. Duchamp (3), ((1) Polish Academy of Sciences, Krakow, Poland, (2)

LPTMC, University of Paris VI, France, (3) Institut Galilee, University of

Paris 13, France)

Categories: quant-ph

Comments: 8 pages, 1 figure

\\

We discuss a general combinatorial framework for operator ordering problems

by applying it to the normal ordering of the powers and exponential of the

boson number operator. The solution of the problem is given in terms of Bell

and Stirling numbers enumerating partitions of a set. This framework reveals

several inherent relations between ordering problems and combinatorial objects,

and displays the analytical background to Wick's theorem. The methodology can

be straightforwardly generalized from the simple example given herein to a wide

class of operators.

\\ ( http://arxiv.org/abs/0704.3116 , 88kb)

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arXiv:0704.3137

Date: Tue, 24 Apr 2007 07:58:46 GMT (169kb)

Title: Scanning magnetoresistance microscopy of atom chips

Authors: M. Volk, S. Whitlock, B. V. Hall, A. I. Sidorov

Categories: physics.atom-ph

Comments: 6 pages, 6 figures

\\

Surface based geometries of microfabricated wires or patterned magnetic films

can be used to magnetically trap and manipulate ultracold neutral atoms or

Bose-Einstein condensates. We investigate the magnetic properties of such atom

chips using a scanning magnetoresistive (MR) microscope with high spatial

resolution and high field sensitivity. We show that MR sensors are ideally

suited to observe small variations of the magnetic field caused by

imperfections in the wires or magnetic materials which ultimately lead to

fragmentation of ultracold atom clouds. Measurements are also provided for the

magnetic field produced by a thin current-carrying wire with small geometric

modulations along the edge. Comparisons of our measurements with a full numeric

calculation of the current flow in the wire and the subsequent magnetic field

show excellent agreement. Our results highlight the use of scanning MR

microscopy as a convenient and powerful technique for precisely characterizing

the magnetic fields produced near the surface of atom chips.

\\ ( http://arxiv.org/abs/0704.3137 , 169kb)

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arXiv:0704.3275

Date: Tue, 24 Apr 2007 21:20:57 GMT (187kb)

Title: Matter-wave interference in s-wave and p-wave Fermi condensates

Authors: Wei Zhang and C. A. R. Sa de Melo

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

Comments: extension of earlier work cond-mat/0603561. 8 pages, 5 figures

\\

We discuss the time evolution and matter-wave interference of Fermi

condensates on the BEC side of Feshbach resonances for $s$ and p-wave

superfluids, upon release from harmonic traps. In s-wave systems, where the

order parameter is a complex scalar, we find that the interference patterns

depend on the relative phase of the order parameters of the condensates. In

p-wave systems involving the mixture of two-hyperfine states, we show that the

interference pattern exhibits a polarization effect depending on the relative

orientation of the two vector order parameters. Lastly, we also point out that

p-wave Fermi condensates exhibit an anisotropic expansion, reflecting the

spatial anisotropy of the underlying interaction between fermions and the

orbital nature of the vector order parameter. Potential applications of our

results include systems of ultra-cold atoms that exhibit p-wave Feshbach

resonances such as $^6$Li or $^{40}$K.

\\ ( http://arxiv.org/abs/0704.3275 , 187kb)

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arXiv:0704.3366

Date: Wed, 25 Apr 2007 13:07:37 GMT (151kb)

Title: Dynamics of a strongly interacting Fermi gas: the radial quadrupole mode

Authors: A. Altmeyer (1), S. Riedl (1 and 2), M. J. Wright (1), C. Kohstall

(1), J. Hecker Denschlag (1) and R. Grimm (1 and 2) ((1) Inst. of

Experimental Physics and Center for Quantum Physics, Univ. Innsbruck,

Technikerstra{\ss}e 25, Austria, (2) Inst. for Quantum Optics and Quantum

Information, Acad. of Sciences, Austria)

Categories: cond-mat.other

Comments: 11 pages, 11 figures

\\

We report on measurements of an elementary surface mode in an ultracold,

strongly interacting Fermi gas of 6Li atoms. The radial quadrupole mode allows

us to probe hydrodynamic behavior in the BEC-BCS crossover without being

influenced by changes in the equation of state. We examine frequency and

damping of this mode, along with its expansion dynamics. In the unitarity limit

and on the BEC side of the resonance, the observed frequencies agree with

standard hydrodynamic theory. However, on the BCS side of the crossover, a

striking down shift of the oscillation frequency is observed in the

hydrodynamic regime as a precursor to an abrupt transition to collisionless

behavior; this indicates coupling of the oscillation to fermionic pairs.

\\ ( http://arxiv.org/abs/0704.3366 , 151kb)

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arXiv:0704.3412

Date: Wed, 25 Apr 2007 17:15:25 GMT (214kb)

Title: The effect of dipole-dipole interactions between atoms in an active

medium

Authors: V.V.Berezovsky, L.I.Men'shikov, S.Oberg and C.D.Latham

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

Comments: 8 pages, 7 figures

\\

Based on the results of numerical modeling, it is shown that dipole-dipole

interactions among atoms in the active medium influences strongly the character

of the associated superradiation. The main effect is to make the nuclear

subsystem behave chaotically. Its strength increases with the atom density, and

leads to the suppression of distant collective correlations and superradiation.

Near correlations between the atoms are established, causing a confinement

effect: a shielding of radiation in the active medium.

\\ ( http://arxiv.org/abs/0704.3412 , 214kb)

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arXiv:0704.3430

Date: Wed, 25 Apr 2007 19:28:34 GMT (273kb)

Title: Prospects for precision measurements of atomic helium using direct

frequency comb spectroscopy

Authors: E. E. Eyler, D. E. Chieda, Matthew C. Stowe, Michael J. Thorpe, T. R.

Schibli, and Jun Ye

Categories: physics.atom-ph

Comments: 14 pages, 6 figures

\\

We analyze several possibilities for precisely measuring electronic

transitions in atomic helium by the direct use of phase-stabilized femtosecond

frequency combs. Because the comb is self-calibrating and can be shifted into

the ultraviolet spectral region via harmonic generation, it offers the prospect

of greatly improved accuracy for UV and far-UV transitions. To take advantage

of this accuracy an ultracold helium sample is needed. For measurements of the

triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap

metastable $2 ^3S$ state atoms. We analyze schemes for measuring the two-photon

$2 ^3S \to 4 ^3S$ interval, and for resonant two-photon excitation to high

Rydberg states, $2 ^3S \to 3 ^3P \to n^3S,D$. We also analyze experiments on

the singlet-state spectrum. To accomplish this we propose schemes for producing

and trapping ultracold helium in the $1 ^1S$ or $2 ^1S$ state via

intercombination transition. A particularly intriguing scenario is the

possibility of direct singlet state spectroscopy, including a measurement of

the $1 ^1S \to 2 ^1S$ transition with extremely high accuracy by use of

two-photon excitation in a magic wavelength trap that operates identically for

both states. We predict a ``triple magic wavelength'' at 412 nm that could

facilitate numerous experiments on trapped helium atoms, because here the

polarizabilities of the $1 ^1S$, $2 ^1S$ and $2 ^3S$ states are all similar,

small, and positive.

\\ ( http://arxiv.org/abs/0704.3430 , 273kb)

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arXiv:0704.3273

Date: Tue, 24 Apr 2007 20:42:25 GMT (37kb)

Title: Forward and non-forward symplectic integrators in solving classical

dynamics problems

Authors: Siu A. Chin

Categories: physics.comp-ph physics.class-ph

Comments: 26 pages, 17 figures, to be published in a "Special Issue on

Splitting Methods for Differential Equation", Intl. J. of Comp. Math

\\

Forward time step integrators are splitting algorithms with only positive

splitting coefficients. When used in solving physical evolution equations,

these positive coefficients correspond to positive time steps. Forward

algorithms are essential for solving time-irreversible equations that cannot be

evolved using backward time steps. However, forward integrators are also better

in solving time-reversible equations of classical dynamics by tracking as

closely as possible the physical trajectory. This work compares in detail

various forward and non-forward fourth-order integrators using three, fourth,

five and six force evaluations. In the case of solving the 2D Kepler orbit, all

non-forward integrators are optimized by simply minimizing the size of their

backward time steps.

\\ ( http://arxiv.org/abs/0704.3273 , 37kb)

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arXiv:0704.3439

Date: Wed, 25 Apr 2007 21:49:31 GMT (36kb)

Title: Dilute two-component Fermi superfluids and the symmetric heavy-light

ansatz

Authors: Dean Lee (North Carolina State University)

Categories: cond-mat.supr-con

Comments: 32 pages, 6 figures

\\

The symmetric heavy-light ansatz is an approximate method for finding the

superfluid ground state of dilute fermions with two degenerate components.

While the Hamiltonian has an exact SU(2) symmetry, the heavy-light ansatz

breaks this symmetry by skewing the mass ratio of the two components. In the

limit where one component is infinitely heavy, the many-body problem can be

solved in terms of single-particle orbitals. The original SU(2) symmetry is

then reintroduced by requiring N-body density correlations for the two

components be equal for all N. In the simple approximation where only the

lowest orbitals are filled, the method is exact for the two-body system, exact

in the strong-coupling Bose gas limit, exact in the weak-coupling Fermi gas

limit, and in good agreement with recent lattice Monte Carlo results for the

ground state energy at unitarity.

\\ ( http://arxiv.org/abs/0704.3439 , 36kb)

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arXiv:0704.3440

Date: Wed, 25 Apr 2007 22:02:28 GMT (36kb)

Title: Dynamical models and the phase ordering kinetics of the s=1 spinor

condensate

Authors: Subroto Mukerjee Cenke Xu Joel E. Moore

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

Comments: 15 pages with 9 figures

\\

The $s=1$ spinor Bose condensate at zero temperature supports ferromagnetic

and polar phases that combine magnetic and superfluid ordering. We investigate

the formation of magnetic domains at finite temperature and magnetic field in

two dimensions in an optical trap. We study the general ground state phase

diagram of a spin-1 system and focus on a phase that has a magnetic Ising order

parameter and numerically determine the nature of the finite temperature

superfluid and magnetic phase transitions. We then study three different

dynamical models: model A, which has no conserved quantities, model F, which

has a conserved second sound mode and the Gross-Pitaevskii (GP) equation which

has a conserved density and magnetization. We find the dynamic critical

exponent to be the same for models A and F ($z=2$) but different for GP ($z

\approx 3$). Externally imposed magnetization conservation in models A and F

yields the value $z \approx 3$, which demonstrates that the only conserved

density relevant to domain formation is the magnetization density.

\\ ( http://arxiv.org/abs/0704.3440 , 36kb)

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arXiv:0704.3483

Date: Thu, 26 Apr 2007 07:18:31 GMT (35kb)

Title: Collective oscillations of a Bose-Fermi mixture: Effect of unequal mass

of Bose and Fermi particles

Authors: Arup Banerjee

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

Comments: 15 pages, 4 figures

\\

We investigate the effect of different mass of a Bose- and a Fermi-particle

on the collective oscillations of the degenerate boson-fermion mixtures. In

particular we consider the monopole and the quadrupole modes of the

oscillations and study their characters and the frequencies by using

variational-sum-rule approach. We find that for both the modes there exists a

critical value of the ratio of boson-fermion mass below and above which the

character and the frequency of the respective modes are significantly

different.

\\ ( http://arxiv.org/abs/0704.3483 , 35kb)

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arXiv:0704.3522

Date: Thu, 26 Apr 2007 12:07:32 GMT (69kb)

Title: Superradiance and multiple scattering of photons in atomic gases

Authors: A. Gero and E. Akkermans

Categories: cond-mat.mes-hall

Comments: 12 pages, 7 figures

\\

We study the influence of cooperative effects such as superradiance and

subradiance, on the scattering properties of dilute atomic gases. We show that

cooperative effects lead to an effective potential between pairs of atoms that

decays like $1/r$. In the case of superradiance, this potential is attractive

for close enough atoms and can be interpreted as a coherent mesoscopic effect.

We consider a model of multiple scattering of a photon among superradiant pairs

and calculate the elastic mean free path and the group velocity. We study first

the case of a scalar wave which allows to obtain and to understand basic

features of cooperative effects and multiple scattering. We then turn to the

general problem of a vector wave. In both cases, we obtain qualitatively

similar results and derive, for the case of a scalar wave, analytic expressions

of the elastic mean free path and of the group velocity for an arbitrary (near

resonance) detuning.

\\ ( http://arxiv.org/abs/0704.3522 , 69kb)

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arXiv:0704.3460

Date: Thu, 26 Apr 2007 01:05:34 GMT (909kb)

Title: Two-color atom guide and 1D optical lattice using evanescent fields of

high-order transverse modes

Authors: Jian Fu, Xiang Yin, and Limin Tong

Categories: quant-ph

Comments: 18 pages, 12 figures, 1 table

\\

We propose a two-color scheme of atom guide and 1D optical lattice using

evanescent light fields of different transverse modes. The optical waveguide

carries a red-detuned light and a blue-detuned light, with both modes far from

resonance. The atom guide and 1D optical lattice potentials can be transformed

to each other by using a Mach-Zehnder interferometer to accurately control mode

transformation. This might provide a new approach to realize flexible

transition between the guiding and trapping states of atoms.

\\ ( http://arxiv.org/abs/0704.3460 , 909kb)

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The replacements:

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arXiv:0704.1642

replaced with revised version Fri, 20 Apr 2007 18:18:23 GMT (51kb)

Title: Collective excitations of hard-core Bosons at half filling on square and

triangular lattices: Development of roton minima and collapse of roton gap

Authors: Tyler Bryant and Rajiv R. P. Singh

Categories: cond-mat.str-el

Comments: 10 pages, 7 figures

\\ ( http://arxiv.org/abs/0704.1642 , 51kb)

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arXiv:cond-mat/0510436

replaced with revised version Fri, 20 Apr 2007 09:10:22 GMT (38kb)

Title: A simple renormalization group approximation of the groundstate

properties of interacting bosonic systems

Authors: Roman Werpachowski and Jerzy Kijowski

Categories: cond-mat.stat-mech

Comments: RevTex 4, 12 figures (revised and updated); to appear in Physical

Review A

\\ ( http://arxiv.org/abs/cond-mat/0510436 , 38kb)

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arXiv:cond-mat/0608491

replaced with revised version Thu, 19 Apr 2007 21:37:16 GMT (321kb)

Title: Supersolids in confined fermions on one-dimensional optical lattices

Authors: F. Karim Pour, M. Rigol, S. Wessel, A. Muramatsu

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

Comments: 4 pages, 5 figures, published version

Journal-ref: Phys. Rev. B 75, 161104(R) (2007)

DOI: 10.1103/PhysRevB.75.161104

\\ ( http://arxiv.org/abs/cond-mat/0608491 , 321kb)

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arXiv:cond-mat/0608566

replaced with revised version Thu, 19 Apr 2007 20:08:29 GMT (499kb)

Title: Excitations from a Bose-Einstein condensate of magnons in coupled spin

ladders

Authors: V. O. Garlea, A. Zheludev, T. Masuda, L.-P. regnault, E. Ressouche, B.

Brenier, H. Manaka, J.-H. Chung, Y. Qiu, K. Habicht, K. Kiefer and M. Boehm

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

Comments: 4 pages, 4 figures

Journal-ref: Phys. Rev. Lett. 98, 167202 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0608566 , 499kb)

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arXiv:quant-ph/0612129

replaced with revised version Fri, 20 Apr 2007 16:51:44 GMT (66kb)

Title: Photon number states generated from a continuous-wave light source

Authors: Anne E. B. Nielsen and Klaus Molmer

Categories: quant-ph

Comments: 8 pages, 7 figures, v2: shortened version

Journal-ref: Phys. Rev. A 75, 043801 (2007)

\\ ( http://arxiv.org/abs/quant-ph/0612129 , 66kb)

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arXiv:cond-mat/0512537

replaced with revised version Tue, 24 Apr 2007 16:05:20 GMT (29kb)

Title: Dynamical Aspects of Analogue Gravity: The Backreaction of Quantum

Fluctuations in Dilute Bose-Einstein Condensates

Authors: Uwe R. Fischer

Categories: cond-mat.other gr-qc hep-th

Comments: 21+epsilon pages; has appeared in Springer Lecture Notes in Physics

Journal-ref: Lect. Notes Phys. 718, 93-113 (2007)

DOI: 10.1007/3-540-70859-6_5

\\ ( http://arxiv.org/abs/cond-mat/0512537 , 29kb)

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arXiv:cond-mat/0701280

replaced with revised version Tue, 24 Apr 2007 12:33:30 GMT (37kb)

Title: Phase diagram for interacting Bose gases

Authors: K. Morawetz, M. Maennel and M. Schreiber

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

\\ ( http://arxiv.org/abs/cond-mat/0701280 , 37kb)

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arXiv:quant-ph/0703155

replaced with revised version Tue, 24 Apr 2007 13:16:31 GMT (229kb)

Title: Trapping cold atoms near carbon nanotubes: thermal spin flips and

Casimir-Polder potential

Authors: Rachele Fermani, Stefan Scheel, Peter L. Knight

Categories: quant-ph cond-mat.other

Comments: 8 pages, 3 figures

\\ ( http://arxiv.org/abs/quant-ph/0703155 , 229kb)

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arXiv:quant-ph/0609134

replaced with revised version Tue, 24 Apr 2007 19:20:24 GMT (248kb)

Title: Fast Quantum State Control of a Single Trapped Neutral Atom

Authors: Matthew P. A. Jones (LCFIO), Jerome Beugnon (LCFIO), Alpha Ga\"etan

(LCFIO), Junxiang Zhang (LCFIO), Gaetan Messin (LCFIO), Antoine Browaeys

(LCFIO), Philippe Grangier (LCFIO)

Categories: quant-ph

Journal-ref: Physical review A 75 (11/04/2007) 040301(R)

DOI: 10.1103/PhysRevA.75.040301

\\ ( http://arxiv.org/abs/quant-ph/0609134 , 248kb)

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arXiv:0704.2623

replaced with revised version Wed, 25 Apr 2007 14:23:35 GMT (413kb)

Title: Bragg spectroscopy of a superfluid Bose-Hubbard gas

Authors: X. Du, Shoupu Wan, Emek Yesilada, C. Ryu, D. J. Heinzen, Z. X. Liang,

and Biao Wu

Categories: cond-mat.other

Comments: 11 pages, 4 figures

\\ ( http://arxiv.org/abs/0704.2623 , 413kb)

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arXiv:cond-mat/0510675

replaced with revised version Wed, 25 Apr 2007 17:45:39 GMT (119kb)

Title: Spin-correlation functions in ultracold paired atomic-fermion systems:

sum rules, self-consistent approximations, and mean fields

Authors: Zhenhua Yu and Gordon Baym

Categories: cond-mat.other

Comments: 7 pages, 1 figure, content added

Journal-ref: Physical Review A 73, 063601 (2006)

\\ ( http://arxiv.org/abs/cond-mat/0510675 , 119kb)

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arXiv:cond-mat/0612538

replaced with revised version Wed, 25 Apr 2007 17:57:46 GMT (19kb)

Title: Quasi-Adiabatic Continuation in Gapped Spin and Fermion Systems:

Goldstone's Theorem and Flux Periodicity

Authors: M. B. Hastings

Categories: cond-mat.stat-mech

Comments: 19 pages, 2 figures, final version in press at JSTAT

\\ ( http://arxiv.org/abs/cond-mat/0612538 , 19kb)

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arXiv:physics/0611237

replaced with revised version Wed, 25 Apr 2007 15:47:22 GMT (177kb)

Title: Interaction-induced crossover versus finite-size condensation in a

weakly interacting trapped one-dimensional Bose gas

Authors: Isabelle Bouchoule (LCFIO), Karen V. Kheruntsyan (ARC Centre of

Excellence for Quantum-Atom Optics), Gora Shlyapnikov (LPTMS)

Categories: physics.atom-ph cond-mat.other cond-mat.stat-mech

Comments: 4 pages

Journal-ref: Physical Review A 75 (28/03/2007) 031606

\\ ( http://arxiv.org/abs/physics/0611237 , 177kb)

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arXiv:cond-mat/0610536

replaced with revised version Thu, 26 Apr 2007 05:19:03 GMT (77kb)

Title: Bose-Einstein condensation of magnons in magnets with predominant

ferromagnetic interaction

Authors: A. V. Syromyatnikov

Categories: cond-mat.str-el

Comments: 9 pages, 4 figure. The paper has been rewritten considerably. In

particular, discussion of crossovers in the critical temperature in

quasi-low-dimensional magnets is added

Journal-ref: Phys. Rev. B 75, 134421 (2007)

DOI: 10.1103/PhysRevB.75.134421

\\ ( http://arxiv.org/abs/cond-mat/0610536 , 77kb)

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Next one will be in a few minutes....

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 May 14 2007 - 09:54:15 EST

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