Matt's arXiv selection: week ending 11 May 2007.

From: Matthew Davis <>
Date: Mon, 14 May 2007 09:54:40 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <>

At least this one is on time: 22 new preprints, 6 replacements.

Date: Fri, 4 May 2007 13:04:08 GMT (76kb)

Title: Oscillation Frequency Dependence of Non-Classical Rotation Inertia of
   Solid $^4$He
Authors: Y. Aoki, J.C. Graves and H. Kojima
Categories: cond-mat.other cond-mat.stat-mech
Comments: 4 pages, 4 figures
   The non-classical rotational inertia fraction of the identical cylindrical
solid $^4$He below 300 mK is studied at 496 and 1173 Hz by a double resonance
torsional oscillator. Below 35 mK, the fraction is the same at sufficiently low
rim velocities. Above 35 mK, the fraction is greater for the higher than the
lower mode. The dissipation peak of the lower mode occurs at a temperature
$\sim$ 4 mK lower than that of the higher mode. The drive dependence of the two
modes shows that the reduction of the fraction is characterized by critical
velocity, \textit{not} amplitude nor acceleration.
\\ ( , 76kb)
Date: Fri, 4 May 2007 19:22:35 GMT (667kb)

Title: BEC-BCS Crossover of a Trapped Two-Component Fermi Gas with Unequal
Authors: J. von Stecher, C. H. Greene, D. Blume
Categories: cond-mat.other
Comments: 5 pages + appendix, 4 figures
   We determine the energetically lowest lying states in the BEC-BCS crossover
regime of s-wave interacting two-component Fermi gases under harmonic
confinement by solving the many-body Schr\"odinger equation using both an
essentially exact basis set expansion technique and the fixed-node diffusion
Monte Carlo method. The energy is calculated as a function of the s-wave
scattering length $a_s$ for $N=2-20$ fermions and different mass ratios
$\kappa$ of the two species. On the BEC and BCS sides, our energies agree with
analytically-determined first-order correction terms. The scattering length and
the effective range of the dimer-dimer system are extracted up to $\kappa =
20$. Finally, our analysis sheds light on the strongly-interacting unitarity
regime of the trapped system.
\\ ( , 667kb)
Date: Mon, 7 May 2007 03:05:51 GMT (139kb)

Title: Simulation via Direct Computation of Partition Functions
Authors: Cheng Zhang, Jianpeng Ma
Categories: cond-mat.stat-mech
Comments: 11 pages, 3 figures
   A new computer simulation method is presented. It directly and simultaneously
compute the partition functions under various macroscopic thermodynamic
conditions, such as temperatures or volumes. It can be easily scaled to large
systems with flexibility of incorporating Monte Carlo cluster algorithms or
molecular dynamics. High efficiency is shown in simulating large Ising models,
in finding ground states of simple protein models, and in studying liquid-vapor
phase transition of Lennard-Jones system. The method is very simple to
implement and we expect it to be efficient in studying complex systems with
rugged energy landscape, e.g., biological macromolecules.
\\ ( , 139kb)
Date: Mon, 7 May 2007 14:54:21 GMT (46kb)

Title: Precise manipulation of a Bose-Einstein condensate using Bragg
Authors: K. J. Hughes, B. Deissler, J. H. T. Burke and C.A. Sackett
Categories: cond-mat.other
Comments: 5 pages, 3 figures
   The use of off-resonant standing light waves to manipulate ultracold atoms is
investigated. Previous work has illustrated that optical pulses can provide
efficient beam-splitting and reflection operations for atomic wave packets. The
performance of these operations is characterized experimentally using
Bose-Einstein condensates confined in a weak magnetic trap. Under optimum
conditions, fidelities of up to 0.99 for beam splitting and 0.98 for reflection
are observed, and splitting operations of up to third order are achieved. The
dependence of the operations on light intensity and atomic velocity is measured
and found to agree well with theoretical estimates.
\\ ( , 46kb)
Date: Mon, 7 May 2007 16:07:37 GMT (216kb)

Title: Stability of spinor Fermi gases in tight waveguides
Authors: A. del Campo, J. G. Muga, M. D. Girardeau
Categories: cond-mat.other
Comments: 5 pages, 6 figures
   The two and three-body correlation functions of the ground state of an
optically trapped ultracold spin-1/2 Fermi gas (SFG) in a tight waveguide (1D
regime) are calculated in the plane of even and odd-wave coupling constants,
assuming a 1D attractive zero-range odd-wave interaction induced by a 3D p-wave
Feshbach resonance, as well as the usual repulsive zero-range even-wave
interaction stemming from 3D s-wave scattering. The calculations are based on
the exact mapping from the SFG to a ``Lieb-Liniger-Heisenberg'' model with
delta-function repulsions depending on isotropic Heisenberg spin-spin
interactions, and indicate that the SFG should be stable against three-body
recombination in a large region of the coupling constant plane encompassing
parts of both the ferromagnetic and antiferromagnetic phases. However, the
limiting case of the fermionic Tonks-Girardeau gas (FTG), a spin-aligned 1D
Fermi gas with infinitely attractive p-wave interactions, is unstable in this
sense. Effects due to the dipolar interaction and a Zeeman term due to a
resonance-generating magnetic field do not lead to shrinkage of the region of
stability of the SFG.
\\ ( , 216kb)
Date: Mon, 7 May 2007 17:07:22 GMT (228kb)

Title: Localization by entanglement
Authors: Joachim Brand, Sergej Flach, Victor Fleurov, L. S. Schulmann, Denis
Categories: cond-mat.other
Comments: 4 pages, 3 figures
   We study the localization of bosonic atoms in an optical lattice, which
interact in a spatially confined region. The classical theory predicts that
there is no localization below a threshold value for the strength of
interaction that is inversely proportional to the number of participating
atoms. In a full quantum treatment, however, we find that localized states
exist for arbitrarily weak attractive or repulsive interactions for any number
($>1$) of atoms. We further show, using an explicit solution of the
two-particle bound state and an appropriate measure of entanglement, that the
entanglement tends to a finite value in the limit of weak interactions. Coupled
with the non-existence of localization in an optimized quantum product state,
we conclude that the localization exists by virtue of entanglement.
\\ ( , 228kb)
Date: Sun, 6 May 2007 07:32:13 GMT (114kb)

Title: Trapping and cooling a rotating mirror using Laguerre-Gaussian beams
Authors: M. Bhattacharya and P. Meystre
Categories: quant-ph
   We show theoretically that it is possible to trap and cool a macroscopic
rotating mirror consisting of a perfectly reflecting spiral phase element using
orbital angular momentum transfer from a Laguerre-Gaussian optical beam. This
offers a promising route to the placement of the rotor in its quantum
mechanical ground state in the presence of thermal noise. The ability to cool
the torsional mode of an oscillator may help improve the sensitivity of
experiments that attempt to measure the gravitational constant $G$, calibrate
Casimir forces or investigate CP-violating effects.
\\ ( , 114kb)
Date: Fri, 4 May 2007 21:49:38 GMT (432kb)

Title: Spin-exchange collisions of submerged shell atoms below 1 Kelvin
Authors: J. G. E. Harris, S. V. Nguyen, S. C. Doret, W. Ketterle, and J. M.
Categories: physics.atom-ph
Comments: 16 pages, 2 figs
   Angular momentum changing collisions can be suppressed in atoms whose valence
electrons are submerged beneath filled shells of higher principle quantum
number. To determine whether spin-exchange collisions are suppressed in these
"submerged shell" atoms, we measured spin-exchange collisions of six hyperfine
states of Mn at temperatures below 1 K. Although the 3d valence electrons in Mn
are submerged beneath a filled 4s orbital, we find that the spin exchange rate
coefficients are similar to those of Na and H (which are non-submerged shell
\\ ( , 432kb)
Date: Mon, 7 May 2007 23:19:25 GMT (14kb)

Title: Fermionic stabilization and density-wave ground state of a polar
Authors: O.Dutta R. Kanamoto and P.Meystre
Categories: cond-mat.other
   We examine the stability of a trapped dipolar condensate mixed with a
single-component fermion gas at T=0. Whereas pure dipolar condensates with
small s-wave interaction are unstable even for small dipole-dipole interaction
strength, we find that the admixture of fermions can significantly stabilize
them, depending on the strength of the boson-fermion interaction. Within the
stable regime we find a region where a ground state is characterized by a
density wave along the soft trap direction.
\\ ( , 14kb)
Date: Tue, 8 May 2007 18:28:50 GMT (352kb)

Title: Theory of Multidimensional Solitons
Authors: L. D. Carr and Joachim Brand
Categories: cond-mat.other cond-mat.mes-hall
Comments: review paper, to appear as Chapter 5a in "Emergent Nonlinear
   Phenomena in Bose-Einstein Condensates: Theory and Experiment," edited by P.
   G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez
   We review a number of topics germane to higher-dimensional solitons in
Bose-Einstein condensates. For dark solitons, we discuss dark band and planar
solitons; ring dark solitons and spherical shell solitons; solitary waves in
restricted geometries; vortex rings and rarefaction pulses; and multi-component
Bose-Einstein condensates. For bright solitons, we discuss instability,
stability, and metastability; bright soliton engineering, including pulsed atom
lasers; solitons in a thermal bath; soliton-soliton interactions; and bright
ring solitons and quantum vortices. A thorough reference list is included.
\\ ( , 352kb)
Date: Tue, 8 May 2007 19:10:41 GMT (366kb,D)

Title: Radiation pressure self-cooling of a micromirror in a cryogenic
Authors: Simon Groeblacher, Sylvain Gigan, Hannes R. Boehm, Anton Zeilinger,
   Markus Aspelmeyer
Categories: quant-ph
   We demonstrate radiation-pressure cavity-cooling of a mechanical mode of a
micromirror starting from cryogenic temperatures. To achieve that, a
high-finesse Fabry-Perot cavity (F\approx 8000) was actively stabilized inside
a continuous-flow 4He cryostat. We observed optical cooling of the fundamental
mode of a 50mu x 50 mu x 5.4 mu singly-clamped micromirror at \omega_m=3.5 MHz
from an environment temperature of 20 K to approx. 290 mK. This corresponds to
a thermal occupation factor of <n>\approx 1x10^4. The cooling performance is
only limited by the mechanical quality and by the optical finesse of the
system. Heating effects, e.g. due to absorption of photons in the micromirror,
were absent. These results represent a next step towards cavity-cooling a
mechanical oscillator into its quantum ground state.
\\ ( , 366kb)
Date: Wed, 9 May 2007 02:40:59 GMT (243kb)

Title: Superfluidity in two-component fermionic systems
Authors: Mucio A. Continentino, Igor T. Padilha
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 4 pages, 7 figures
   Different types of superfluid ground states have been investigated in systems
of two species of fermions with Fermi surfaces that do not match. This study is
relevant for cold atomic systems, condensed matter physics and quark matter. In
this Letter we consider this problem in the case the fermionic quasi-particles
can transmute into one another and only their total number is conserved. We
study the stability of the superfluid ground state and the nature of the
quantum phase transitions for the cases the attractive interaction is among the
same or different types of fermions. We find a new superfluid state with
features similar to breached pairing superfluidity including gapless
\\ ( , 243kb)
Date: Wed, 9 May 2007 08:33:22 GMT (115kb)

Title: A semi-classical field method for the equilibrium Bose gas and
   application to thermal vortices in two dimensions
Authors: Luca Giorgetti (CNR-BEC-INFM), Iacopo Carusotto (CNR-BEC-INFM), Yvan
   Castin (LKB - Lhomond)
Categories: cond-mat.other
Comments: 19 pages
Proxy: ccsd hal-00145190
   We develop a semi-classical field method for the study of the weakly
interacting Bose gas at finite temperature, which, contrarily to the usual
classical field model, does not suffer from an ultraviolet cut-off dependence.
We apply the method to the study of thermal vortices in spatially homogeneous,
two-dimensional systems. We present numerical results for the vortex density
and the vortex pair distribution function. Insight in the physics of the system
is obtained by comparing the numerical results with the predictions of simple
analytical models. In particular, we calculate the activation energy required
to form a vortex pair at low temperature.
\\ ( , 115kb)
Date: Wed, 9 May 2007 16:50:50 GMT (237kb)

Title: Bright-Dark Soliton Complexes in Spinor Bose-Einstein Condensates
Authors: H.E. Nistazakis, D.J. Frantzeskakis, P.G. Kevrekidis, B.A. Malomed, R.
Categories: cond-mat.other
Comments: 8 pages, 2 figures
   We present novel solutions for bright-dark vector solitons in
quasi-one-dimensional spinor (F=1) Bose-Einstein condensates. Using a
multiscale expansion technique, we reduce the corresponding system of three
coupled Gross-Pitaevskii equations (GPEs) to a completely integrable
Yajima-Oikawa system. In this way, we obtain approximate solutions for
small-amplitude vector solitons of dark-dark-bright and bright-bright-dark
types, in terms of the $m_{F}=+1,-1,0$ spinor components, respectively. By
means of numerical simulations of the full GPE system, we demonstrate that
these states feature solitary wave properties, i.e., they propagate undistorted
and undergo quasi-elastic collisions. It is also shown that, in the presence of
a parabolic trap of strength $\omega$, the bright component(s) are guided by
the dark one(s), so that the vector soliton as a whole performs harmonic
oscillations of frequency $\omega/\sqrt{2}$.
\\ ( , 237kb)
Date: Wed, 9 May 2007 17:58:14 GMT (1108kb)

Title: Experiments on Multidimensional Solitons
Authors: Joachim Brand, L. D. Carr, and B. P. Anderson
Categories: cond-mat.other cond-mat.mes-hall
Comments: review paper, to appear as Chapter 5b in "Emergent Nonlinear
   Phenomena in Bose-Einstein Condensates: Theory and Experiment," edited by P.
   G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez
   This article presents an overview of experimental efforts in recent years
related to multidimensional solitons in Bose-Einstein condensates. We discuss
the techniques used to generate and observe multidimensional nonlinear waves in
Bose-Einstein condensates with repulsive interactions. We further summarize
observations of planar soliton fronts undergoing the snake instability, the
formation of vortex rings, and the emergence of hybrid structures.
\\ ( , 1108kb)
arXiv:0705.1107 (*cross-listing*)
Date: Tue, 8 May 2007 14:51:30 GMT (31kb)

Title: The TF Limit for Rapidly Rotating Bose Gases in Anharmonic Traps
Authors: J.-B. Bru, M. Correggi, P. Pickl, J. Yngvason
Categories: math-ph cond-mat.other math.MP
MSC-class: 35Q55, 47J30, 76M23
   Starting from the full many body Hamiltonian we derive the leading order
energy and density asymptotics for the ground state of a dilute, rotating Bose
gas in an anharmonic trap in the ` Thomas Fermi' (TF) limit when the
Gross-Pitaevskii coupling parameter and/or the rotation velocity tend to
infinity. Although the many-body wave function is expected to have a
complicated phase, the leading order contribution to the energy can be computed
by minimizing a simple functional of the density alone.
\\ ( , 31kb)
Date: Wed, 9 May 2007 00:43:07 GMT (259kb)

Title: Deflection of Slow Light by Magneto-Optically Controlled Atomic Media
Authors: D.L. Zhou, Lan Zhou, S. Yi, C.P. Sun
Categories: quant-ph
Comments: 4 pages, 3 figures
   We present a semi-classical theory for light deflection by a coherent atomic
medium with $\Lambda$ configuration in an inhomogeneous magnetic field or a
driving field with a spatially distributed profile. When the atomic energy
levels (or Rabi couplings to the controlling field) are position-dependent due
to the Zeeman effect by the inhomogeneous magnetic field (or the inhomogeneity
of the control field profile), the spatial dependence of the refraction index
of the atomic medium will lay out an observable deflection of slow light when
the electromagnetically induced transparency happens to avoid medium
absorption. Our theoretical approach based on the Fermat's principle in
geometrical optics not only provides a consistent explanation for the most
recent experiment in a straightforward way, but also predicts the new effects
for the weak slow light deflection by optically controlled atomic media in the
off-resonant case with control field of inhomogeneous profile.
\\ ( , 259kb)
Date: Wed, 9 May 2007 11:11:45 GMT (71kb)

Title: A method of state-selective transfer of atoms between microtraps based
   on the Franck-Condon Principle
Authors: A. B. Deb, G. Smirne, R. M. Godun, C. J. Foot
Categories: physics.atom-ph
Comments: 7 pages, 4 figures
   We present a method of transferring a cold atom between spatially separated
microtraps by means of a Raman transition between the ground motional states of
the two traps. The intermediate states for the Raman transition are the
vibrational levels of a third microtrap, and we determine the experimental
conditions for which the overlap of the wave functions leads to an efficient
transfer. There is a close analogy with the Franck-Condon principle in the
spectroscopy of molecules. Spin-dependent manipulation of neutral atoms in
microtraps has important applications in quantum information processing. We
also show that starting with several atoms, precisely one atom can be
transferred to the final potential well hence giving deterministic preparation
of single atoms.
\\ ( , 71kb)
Date: Wed, 9 May 2007 14:21:09 GMT (888kb)

Title: Ultracold Rydberg Atoms in a Ioffe-Pritchard Trap
Authors: Bernd Hezel, Igor Lesanovsky, Peter Schmelcher
Categories: physics.atom-ph
Comments: 30 pages, 10 figures
   We discuss the properties of ultracold Rydberg atoms in a Ioffe-Pritchard
magnetic field configuration. The derived two-body Hamiltonian unveils how the
large size of Rydberg atoms affects their coupling to the inhomogeneous
magnetic field. The properties of the compound electronic and center of mass
quantum states are thoroughly analyzed. We find very tight confinement of the
center of mass motion in two dimensions to be achievable while barely changing
the electronic structure compared to the field free case. This paves the way
for generating a one-dimensional ultracold quantum Rydberg gas.
\\ ( , 888kb)
Date: Thu, 10 May 2007 15:48:45 GMT (32kb)

Title: Three fermions in a box at the unitary limit: universality in a lattice
Authors: Ludovic Pricoupenko (LPTMC), Yvan Castin (LKB - Lhomond)
Categories: cond-mat.other
Comments: 6 pages
Proxy: ccsd hal-00145589
   We consider three fermions with two spin components interacting on a lattice
model with an infinite scattering length. Low lying eigenenergies in a cubic
box with periodic boundary conditions, and for a zero total momentum, are
calculated numerically for decreasing values of the lattice period. The results
are compared to the predictions of the zero range Bethe-Peierls model in
continuous space, where the interaction is replaced by contact conditions. The
numerical computation, combined with analytical arguments, shows the absence of
negative energy solution, and a rapid convergence of the lattice model towards
the Bethe-Peierls model for a vanishing lattice period. This establishes for
this system the universality of the zero interaction range limit.
\\ ( , 32kb)
Date: Thu, 10 May 2007 03:09:13 GMT (13kb)

Title: Bell inequalities for continuous-variables correlations
Authors: E. G. Cavalcanti, C. J. Foster and P. D. Drummond
Categories: quant-ph
Comments: 4 pages, 1 figure
   We derive a new class of correlation Bell-type inequalities. The inequalities
are valid for any number of outcomes of two observables per each of n parties,
including continuous and unbounded observables. We show that there are no
first-moment correlation Bell inequalities for that scenario, but such
inequalities can be found if one considers at least second moments. The
derivation stems from a simple variance inequality by setting local commutators
to zero, and can be used to derive other well-known Bell inequalities, shedding
new light on the importance of non-commutativity for violations of local
\\ ( , 13kb)
Date: Thu, 10 May 2007 13:57:35 GMT (244kb)

Title: Accumulation of chromium metastable atoms into an Optical Trap
Authors: R. Chicireanu, Q. Beaufils, A. Pouderous, B. Laburthe-Tolra, E.
   Marechal, L. Vernac, J.-C. Keller, and O. Gorceix
Categories: physics.atom-ph
Comments: 7 pages, 5 Figures
   We report the fast accumulation of a large number of metastable 52Cr atoms in
a mixed trap, formed by the superposition of a strongly confining optical trap
and a quadrupolar magnetic trap. The steady state is reached after about 400
ms, providing a cloud of more than one million metastable atoms at a
temperature of about 100 microK, with a peak density of 10^{18} atoms.m^{-3}.
We have optimized the loading procedure, and measured the light shift of the
5D4 state by analyzing how the trapped atoms respond to a parametric
excitation. We compare this result to a theoretical evaluation based on the
available spectroscopic data for chromium atoms.
\\ ( , 244kb)


replaced with revised version Mon, 7 May 2007 19:00:39 GMT (281kb)

Title: Quench dynamics and non equilibrium phase diagram of the Bose-Hubbard
Authors: Corinna Kollath, Andreas Laeuchli, and Ehud Altman
Categories: cond-mat.other
Journal-ref: Phys. Rev. Lett. 98, 180601 (2007)
DOI: 10.1103/PhysRevLett.98.180601
\\ ( , 281kb)
replaced with revised version Mon, 7 May 2007 16:03:09 GMT (243kb)

Title: Classical simulation of infinite-size quantum lattice systems in two
   spatial dimensions
Authors: J. Jordan, R. Orus, G. Vidal, F. Verstraete, J. I. Cirac
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 5 pages, 7 figures
\\ ( , 243kb)
arXiv:nucl-th/0611097 (*cross-listing*)
replaced with revised version Sat, 5 May 2007 10:13:36 GMT (75kb)

Title: Relativistic BCS-BEC crossover in a boson-fermion model
Authors: Jian Deng, Andreas Schmitt, Qun Wang
Categories: nucl-th cond-mat.supr-con hep-ph
Comments: ReVTex4, 19 pages, 10 figures; new chapter added about the case of
   imbalanced fermion populations; minor modifications to main part; references
\\ ( , 75kb)
replaced with revised version Tue, 8 May 2007 14:25:43 GMT (11kb)

Title: The depletion in Bose Einstein condensates using Quantum Field Theory in
   curved space
Authors: Roberto Balbinot, Serena Fagnocchi, Alessandro Fabbri
Categories: cond-mat.other cond-mat.soft gr-qc
Comments: 4 pages, no figure. Discussion extended and references added
Journal-ref: Phys. Rev. A 75, 043622 (2007)
DOI: 10.1103/PhysRevA.75.043622
\\ ( , 11kb)
replaced with revised version Thu, 10 May 2007 08:20:11 GMT (81kb)

Title: Density-density correlation and interference mechanism for two initially
   independent Bose-Einstein condensates
Authors: Shujuan Liu, Hongwei Xiong
Categories: cond-mat.stat-mech
Comments: See also cond-mat/0612132 (or New Journal of Physics 8, 245 (2006))
\\ ( , 81kb)
replaced with revised version Thu, 10 May 2007 10:22:26 GMT (654kb)

Title: Resonance fluorescence of a cold atom in a high-finesse resonator
Authors: Marc Bienert, J. Mauricio Torres, Stefano Zippilli, Giovanna Morigi
Categories: quant-ph cond-mat.other physics.atom-ph
Comments: 10 pages, 7 figures,version accepted for publication in Phys. Rev. A
\\ ( , 654kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Mon May 14 2007 - 09:54:40 EST

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