Matt's arXiv selection: week ending 28 December 2007.

From: Matthew Davis <>
Date: Fri, 04 Jan 2008 19:33:07 +1000

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

Hi all,

Happy New Year, and welcome to the first mailing of 2008! Despite it being the
week of Christmas, there were still 20 new preprints and 8 replacements this week.

Date: Thu, 20 Dec 2007 21:28:05 GMT (17kb)

Title: Coherent oscillations in superconducting cold Fermi atoms and their
Authors: Razvan Teodorescu
Categories: cond-mat.str-el quant-ph
Comments: Invited chapter in "Leading-edge Superconductivity Research
   Developments", Nova
Report-no: LA-UR-07-2504
   Recent achievements in experiments with cold fermionic atoms indicate the
potential for developing novel superconducting devices which may be operated in
a wide range of regimes, at a level of precision previously not available.
Unlike traditional, solid-state superconducting devices, the cold-atom systems
allow the fast switching on of the BCS phase, and the observation of
non-equilibrium, coherent oscillations of the order parameter. The integrable
and non-linear nature of the equations of motions makes this operating regime
particularly rich in potential applications, such as quantum modulation and
encoding, or nonlinear mixing of quantum coherent oscillations, to name only
two. From a mathematical point of view, such systems can be described using the
Knizhnik-Zamolodchikov-Bernard equation, or more generally, by the matrix
Kadomtsev-Petviashvilii integrable hierarchy. This identification is
particularly useful, since it allows a direct application of the known
non-linear phenomena described by particular solutions of these equations.
Other important features of this formulation, such as the relation to the spin
Calogero-Sutherland model, also have relevant physical interpretations. In this
work, a complete description of these relationships is presented, along with
their potential practical consequences.
\\ ( , 17kb)
Date: Fri, 21 Dec 2007 14:17:59 GMT (194kb)

Title: Off-diagonal Ground State Properties of a 1D Gas of Fermi Hard Rods
Authors: F.Mazzanti, G.E.Astrakharchik, J.Boronat, J.Casulleras
Categories: cond-mat.stat-mech
Comments: 5 figures
   A variational Monte Carlo calculation of the one-body density matrix and
momentum distribution of a system of Fermi hard rods (HR) is presented and
compared with the same quantities for its bosonic counterpart. The calculation
is exact within statistical errors since we sample the exact ground state wave
function, whose analytical expression is known. The numerical results are in
good agreement with known asymptotic expansions valid for Luttinger liquids. We
find that the difference between the absolute value of the bosonic and
fermionic density matrices becomes marginally small as the density increases.
In this same regime, the corresponding momentum distributions merge into a
common profile that is independent of the statistics. Non-analytical
contributions to the one--body density matrix are also discussed and found to
be less relevant with increasing density.
\\ ( , 194kb)
Date: Fri, 21 Dec 2007 00:24:41 GMT (49kb)

Title: Dilute Bose gases interacting via power-law potentials
Authors: Ryan M. Kalas, D. Blume
Categories: cond-mat.other
Comments: 7 pages, 4 figures
   Neutral atoms interact through a van der Waals potential which asymptotically
falls off as r^{-6}. In ultracold gases, this interaction can be described to a
good approximation by the atom-atom scattering length. However, corrections
arise that depend on the characteristic length of the van der Waals potential.
We parameterize these corrections by analyzing the energies of two- and
few-atom systems under external harmonic confinement, obtained by numerically
and analytically solving the Schrodinger equation. We generalize our results to
particles interacting through a longer-ranged potential which asymptotically
falls off as r^{-4}.
\\ ( , 49kb)
Date: Fri, 21 Dec 2007 20:52:18 GMT (19kb)

Title: Stability of dark solitons in three dimensional dipolar Bose-Einstein
Authors: R. Nath, P. Pedri and L. Santos
Categories: cond-mat.other
Comments: 4 pages, 3 eps figures
   The dynamical stability of dark solitons in dipolar Bose-Einstein condensates
is studied. For standard short-range interacting condensates dark solitons are
unstable against transverse excitations in two and three dimensions. On the
contrary, due to its non local character, the dipolar interaction allows for
stable 3D stationary dark solitons, opening a qualitatively novel scenario in
nonlinear atom optics. We discuss in detail the conditions to achieve this
stability, which demand the use of an additional optical lattice, and the
stability regimes.
\\ ( , 19kb)
Date: Fri, 21 Dec 2007 11:43:08 GMT (413kb)

Title: Sinusoidal Excitations in Two Component Bose-Einstein Condensates
Authors: Priyam Das, T. Solomon Raju, Utpal Roy and Prasanta K. Panigrahi
Categories: cond-mat.other
Comments: 6 pages, 1 figure
   The non-linear coupled Gross-Pitaevskii equation governing the dynamics of
the two component Bose-Einstein condensate (TBEC) is shown to admit pure
sinusoidal, propagating wave solutions in quasi one dimensional geometry. These
solutions, which exist for a wide parameter range, are then investigated in the
presence of a harmonic oscillator trap with time dependent scattering length.
This illustrates the procedure for coherent control of these modes through
temporal modulation of the parameters, like scattering length and oscillator
frequency. We subsequently analyzed this system in an optical lattice, where
the occurrence of an irreversible phase transition from superfluid to insulator
phase is seen.
\\ ( , 413kb)
Date: Thu, 20 Dec 2007 21:39:18 GMT (528kb)

Title: Mapping photonic entanglement into and out of a quantum memory
Authors: K. S. Choi, H. Deng, J. Laurat, and H. J. Kimble
Categories: quant-ph
Comments: 7 pages, and 3 figures
   Recent developments of quantum information science critically rely on
entanglement, an intriguing aspect of quantum mechanics where parts of a
composite system can exhibit correlations stronger than any classical
counterpart. In particular, scalable quantum networks require capabilities to
create, store, and distribute entanglement among distant matter nodes via
photonic channels. Atomic ensembles can play the role of such nodes. So far, in
the photon counting regime, heralded entanglement between atomic ensembles has
been successfully demonstrated via probabilistic protocols. However, an
inherent drawback of this approach is the compromise between the amount of
entanglement and its preparation probability, leading intrinsically to low
count rate for high entanglement. Here we report a protocol where entanglement
between two atomic ensembles is created by coherent mapping of an entangled
state of light. By splitting a single-photon and subsequent state transfer, we
separate the generation of entanglement and its storage. After a programmable
delay, the stored entanglement is mapped back into photonic modes with overall
efficiency of 17 %. Improvements of single-photon sources together with our
protocol will enable "on demand" entanglement of atomic ensembles, a powerful
resource for quantum networking.
\\ ( , 528kb)
Date: Fri, 21 Dec 2007 08:18:44 GMT (8448kb)

Title: Atom Interferometers
Authors: Alexander D. Cronin, Joerg Schmiedmayer, David E. Pritchard
Categories: quant-ph
Comments: submitted to Reviews of Modern Physics
   Interference with atomic and molecular matter waves is a rich branch of
atomic physics and quantum optics. It started with atom diffraction from
crystal surfaces and the separated oscillatory fields technique used in atomic
clocks. Atom interferometry is now reaching maturity as a powerful art with
many applications in modern science. In this review we first describe the basic
tools for coherent atom optics including diffraction by nanostructures and
laser light, three-grating interferometers, and double wells on AtomChips. Then
we review scientific advances in a broad range of fields that have resulted
from the application of atom interferometers. These are grouped in three
categories: (1) fundamental quantum science, (2) precision metrology and (3)
atomic and molecular physics. Although some experiments with Bose Einstein
condensates are included, the focus of the review is on linear matter wave
optics, i.e. phenomena where each single atom interferes with itself.
\\ ( , 8448kb)
arXiv:0712.3438 (*cross-listing*)
Date: Thu, 20 Dec 2007 07:03:24 GMT (1194kb)

Title: Consequences of Zeeman Degeneracy for van der Waals Blockade between
   Rydberg Atoms
Authors: Thad G. Walker and M. Saffman
Categories: quant-ph physics.atom-ph
Comments: 16 figures
   We analyze the effects of Zeeman degeneracies on the long-range interactions
between like Rydberg atoms, with particular emphasis on applications to quantum
information processing using van der Waals blockade. We present a general
analysis of how degeneracies affect the primary error sources in blockade
experiments, emphasizing that blockade errors are sensitive primarily to the
weakest possible atom-atom interactions between the degenerate states, not the
mean interaction strength. We present explicit calculations of the van der
Waals potentials in the limit where the fine-structure interaction is large
compared to the atom-atom interactions. The results are presented for all
potential angular momentum channels invoving s, p, and d states. For most
channels there are one or more combinations of Zeeman levels that have
extremely small dipole-dipole interactions and are therefore poor candidates
for effective blockade experiments. Channels with promising properties are
identified and discussed. We also present numerical calculations of Rb and Cs
dipole matrix elements and relevant energy levels using quantum defect theory,
allowing for convenient quantitative estimates of the van der Waals
interactions to be made for principal quantum numbers up to 100. Finally, we
combine the blockade and van der Waals results to quantitatively analyze the
angular distribution of the blockade shift and its consequence for angular
momentum channels and geometries of particular interest for blockade
experiments with Rb.
\\ ( , 1194kb)
arXiv:0712.3572 (*cross-listing*)
Date: Thu, 20 Dec 2007 21:21:11 GMT (98kb,D)

Title: A Quantitative Measure of Experimental Scientific Merit
Authors: Bruce Knuteson
Categories: hep-ex hep-ph hep-th physics.soc-ph
Comments: 14 pages
   Experimental program review in our field may benefit from a more quantitative
framework within which to quantitatively discuss the scientific merit of a
proposed program of research, and to assess the scientific merit of a
particular experimental result. This article proposes explicitly such a
quantitative framework. Examples of the use of this framework in assessing the
scientific merit of particular avenues of research at the energy frontier in
many cases provide results in stark contradiction to accepted wisdom. The
experimental scientific figure of merit proposed here has the potential for
informing future choices of research direction in our field, and in other
subfields of the physical sciences.
\\ ( , 98kb)
Date: Sat, 22 Dec 2007 11:58:59 GMT (29kb)

Title: Nonlinear behavior of bosons in anisotropic optical lattices
Authors: A. Cetoli, E. Lundh
Categories: cond-mat.other
Comments: 5 pages, 4 figures
   We investigate the behavior of a one-dimensional array of
   Bose-Einstein condensate tubes described by means of a Bose-Hubbard
   Hamiltonian. Using an anisotropic non-polynomial Schr\"odinger equation we
link the macroscopic parameters in the Bose-Hubbard Hamiltonian to the ones
that are tunable in experiments. Using a mean field approach we predict that
increasing the optical lattice strength along the direction of the tubes, the
condensate can experience a reentrant transition between a Mott insulating
phase and the superfluid one.
\\ ( , 29kb)
Date: Sat, 22 Dec 2007 16:19:43 GMT (170kb)

Title: Resonant tunneling of Bose-Einstein condensates in optical lattices
Authors: Alessandro Zenesini, Carlo Sias, Hans Lignier, Yeshpal Singh,
   Donatella Ciampini, Oliver Morsch, Riccardo Mannella, Ennio Arimondo, Andrea
   Tomadin, and Sandro Wimberger
Categories: cond-mat.other
Comments: 16 pages, 7 figures
   In this article, we present theoretical as well as experimental results on
resonantly enhanced tunneling of Bose-Einstein condensates in optical lattices
both in the linear case and for small nonlinearities. Our results demonstrate
the usefulness of condensates in optical lattices for simulating Hamiltonians
originally used for describing solid state phenomena.
\\ ( , 170kb)
Date: Sun, 23 Dec 2007 01:24:17 GMT (144kb)

Title: Heteronuclear molecules in an optical dipole trap
Authors: J. J. Zirbel, K.-K. Ni, S. Ospelkaus, T. L. Nicholson, M. L. Olsen, C.
   E. Wieman, J. Ye, D. S. Jin, and P. S. Julienne
Categories: cond-mat.other
Comments: 7 pages, 7 figures
   We report on the creation and characterization of heteronuclear KRb Feshbach
molecules in an optical dipole trap. Starting from an ultracold gas mixture of
K-40 and Rb-87 atoms, we create as many as 25,000 molecules at 300 nK by rf
association. Optimizing the association process, we achieve a conversion
efficiency of 25%. We measure the temperature dependence of the rf association
process and find good agreement with a phenomenological model that has
previously been applied to Feshbach molecule creation by slow magnetic-field
sweeps. We also present a measurement of the binding energy of the
heteronuclear molecules in the vicinity of the Feshbach resonance and provide
evidence for Feshbach molecules as deeply bound as 26 MHz.
\\ ( , 144kb)
Date: Wed, 26 Dec 2007 13:33:23 GMT (370kb)

Title: Gap solitons in superfluid boson-fermion mixtures
Authors: Sadhan K. Adhikari and Boris A. Malomed
Categories: cond-mat.other
Comments: 9 pages, 14 figures
Journal-ref: Phys. Rev. A 76 (2007) 043626 (pp1-9)
   Using coupled equations for the bosonic and fermionic order parameters, we
construct families of gap solitons (GSs) in a nearly one-dimensional Bose-Fermi
mixture trapped in a periodic optical-lattice (OL) potential, the boson and
fermion components being in the states of the BEC and BCS superfluid,
respectively. Fundamental GSs are compact states trapped, essentially, in a
single cell of the lattice. Full families of such solutions are constructed in
the first two bandgaps of the OL-induced spectrum, by means of variational and
numerical methods, which are found to be in good agreement. The families
include both intra-gap and inter-gap solitons, with the chemical potentials of
the boson and fermion components falling in the same or different bandgaps,
respectively.Nonfundamental states, extended over several lattice cells, are
constructed too. The GSs are stable against strong perturbations.
\\ ( , 370kb)
Date: Sun, 23 Dec 2007 22:59:55 GMT (50kb)

Title: Build-up of coherence between initially-independent subsystems: The case
   of Bose-Einstein condensates
Authors: O. E. Alon, A. I. Streltsov, and L. S. Cederbaum
Categories: cond-mat.other
Comments: 11 pages, 3 figures
   When initially-independent subsystems are made to contact, {\it coherence}
can develop due to interaction between them. We exemplify and demonstrate this
paradigm through several scenarios of two initially-independent Bose-Einstein
condensates which are allowed to collide. The build-up of coherence depends
strongly on time, interaction strength and other parameters of each condensate.
Implications are discussed.
\\ ( , 50kb)
Date: Tue, 25 Dec 2007 14:32:11 GMT (531kb,D)

Title: Quantum Phases of Trapped Ions in an Optical Lattice
Authors: Roman Schmied, Tommaso Roscilde, Valentin Murg, Diego Porras, J.
   Ignacio Cirac
Categories: cond-mat.str-el
   We propose loading trapped ions into microtraps formed by an optical lattice.
For harmonic microtraps, the Coulomb coupling of the spatial motions of
neighboring ions can be used to construct a broad class of effective
short-range Hamiltonians acting on an internal degree of freedom of the ions.
For large anharmonicities, on the other hand, the spatial motion of the ions
itself represents a spin-1/2 model with frustrated dipolar XY interactions. We
illustrate the latter setup with three systems: the linear chain, the zig-zag
ladder, and the triangular lattice. In the frustrated zig-zag ladder with
dipolar interactions we find chiral ordering beyond what was predicted
previously for a next-nearest-neighbor model. In the frustrated anisotropic
triangular lattice with nearest-neighbor interactions we find that the
transition from the one-dimensional gapless spin-liquid phase to the
two-dimensional spiraling ordered phase passes through a gapped spin-liquid
phase, similar to what has been predicted for the same model with Heisenberg
interactions. Further, a second gapped spin-liquid phase marks the transition
to the two-dimensional Neel-ordered phase.
\\ ( , 531kb)
Date: Tue, 25 Dec 2007 19:05:15 GMT (13kb)

Title: Isospin excitations of a trapped 1D gas of attractively interacting
Authors: M. Colom\'e-Tatch\'e, G. V. Shlyapnikov and A. M. Tsvelik
Categories: cond-mat.str-el
   We consider a gas of fermions with a short-range attractive intercomponent
interaction in a parabolic external potential and derive the conditions of the
local density approximation. The obtained spectrum of quasiparticle (isospin)
excitations shows equidistant low-energy levels, which is equivalent to a
linear momentum dependence and is fundamentally different from the ordinary
Dirac spectrum in the spatially uniform case.
\\ ( , 13kb)
Date: Thu, 27 Dec 2007 07:06:05 GMT (97kb)

Title: Many-Body Effects on Nonadiabatic Feshbach Conversion in Bosonic Systems
Authors: jie liu, Bin Liu, and Libin Fu
Categories: cond-mat.mes-hall
Comments: 7pages 5figures
   We investigate the dynamics of converting cold bosonic atoms to molecules
when an external magnetic field is swept across a Feshbach resonance. Our
analysis relies on a zero temperature quantum microscopic model that accounts
for many-body effects, triggering the association process. We show that the
picture of two-body molecular production depicted by Landau-Zener model is
significantly altered due to many-body effects. In nonadiabatic regime, we
derive an analytic expression for molecular conversion efficiency that explains
the discrepancy between the prediction of Landau-Zener formula and experimental
data[Hodby et al., Phys. Rev. Lett. {\bf 94}, 120402 (2005)]. Our theory is
further extended to the formation of heteronuclear diatomic molecules and gives
some interesting predictions.
\\ ( , 97kb)
Date: Thu, 27 Dec 2007 19:42:31 GMT (153kb)

Title: A vortex dipole in a trapped two-dimensional Bose-Einstein condensate
Authors: Weibin Li, Masudul Haque, Stavros Komineas
Categories: cond-mat.other cond-mat.mes-hall
Comments: 6+ pages, 8 figures
   We study the conservative dynamics and stationary configurations of a
vortex-antivortex pair in a harmonically trapped two-dimensional Bose-Einstein
condensate. We establish the conceptual framework for understanding the
stationary states and the topological defect trajectories, through
considerations of different mechanisms of vortex motion and the bifurcation of
soliton-like stationary solutions. Our insights are based on Lagrangian-based
variational calculations, numerical solutions of both the time-dependent and
time-independent Gross-Pitaevskii equations, and exact solutions for the
non-interacting case.
\\ ( , 153kb)
Date: Thu, 27 Dec 2007 20:50:07 GMT (45kb)

Title: The dynamics of developing Cooper pairing at finite temperatures
Authors: Emil A. Yuzbashyan and Oleksandr Tsyplyatyev
Categories: cond-mat.supr-con cond-mat.mes-hall
Comments: 4 pages, 1 figure
   We study the time evolution of a system of fermions with pairing interactions
at a finite temperature. The dynamics is triggered by an abrupt increase of the
BCS coupling constant. We show that if initially the fermions are in a normal
phase, the amplitude of the BCS order parameter averaged over the Boltzman
distribution of initial states exhibits damped oscillations with a relatively
short decay time. The latter is determined by the temperature, the
single-particle level spacing, and the ground state value of the BCS gap for
the new coupling. In contrast, the decay is essentially absent when the system
was in a superfluid phase before the coupling increase.
\\ ( , 45kb)
Date: Thu, 27 Dec 2007 03:00:01 GMT (223kb)

Title: Spontaneously modulated spin textures in a dipolar spinor Bose-Einstein
Authors: M. Vengalattore, S. R. Leslie, J. Guzman and D. M. Stamper-Kurn
Categories: quant-ph
   Helical spin textures in a $^{87}$Rb F=1 spinor Bose-Einstein condensate are
found to decay spontaneously toward a spatially modulated structure of spin
domains. This evolution is ascribed to magnetic dipolar interactions that
energetically favor the short-wavelength domains over the long-wavelength spin
helix. This is confirmed by eliminating the dipolar interactions by a sequence
of rf pulses and observing a suppression of the formation of the short-range
domains. This study confirms the significance of magnetic dipole interactions
in degenerate $^{87}$Rb F=1 spinor gases.
\\ ( , 223kb)

The replacements:

replaced with revised version Thu, 20 Dec 2007 22:45:54 GMT (359kb)

Title: Universal properties of a trapped two-component Fermi gas at unitarity
Authors: D. Blume, J. von Stecher and Chris H. Greene
Categories: cond-mat.other
Comments: 4 pages, 2 Figs., 2 Tables (minor changes)
Journal-ref: Phys. Rev. Lett. 99, 233201 (2007)
\\ ( , 359kb)
replaced with revised version Fri, 21 Dec 2007 19:42:13 GMT (136kb)

Title: Density correlations in ultracold Fermi systems within the exact
   Richardson solution
Authors: S. Staudenmayer, W. Belzig, C. Bruder
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 8 pages, 7 figures, minor revisions, references added, to be
   published in PRA
\\ ( , 136kb)
replaced with revised version Fri, 21 Dec 2007 20:15:55 GMT (828kb,D)

Title: Observing Zitterbewegung in Ultracold Atoms
Authors: J. Y. Vaishnav, Charles W. Clark
Categories: cond-mat.mes-hall
Comments: 4 pages, 5 figures. Added references
\\ ( , 828kb)
replaced with revised version Fri, 21 Dec 2007 15:04:22 GMT (430kb)

Title: Mode Locking of Exciton-Polariton Condensates in the Presence of
Authors: A. Baas, K. G. Lagoudakis, M. Richard, R. Andre, Le Si Dang, B.
Categories: cond-mat.other
Comments: 10 pages, 4 figures,corrected typos and figure details
\\ ( , 430kb)
replaced with revised version Fri, 21 Dec 2007 13:38:32 GMT (810kb,D)

Title: Integer quantum Hall effect in constant non-Abelian "magnetic" fields
Authors: N. Goldman, A. Kubasiak, P. Gaspard and M. Lewenstein
Categories: cond-mat.mes-hall
Comments: 4 pages, 4 figures
\\ ( , 810kb)
replaced with revised version Fri, 21 Dec 2007 23:04:54 GMT (953kb)

Title: Coherent Control of Trapped Bosons
Authors: Analabha Roy, Linda E. Reichl
Categories: physics.atom-ph
Comments: 17 figures, Appended a paragraph on section 1 and explained details
   behind the hamiltonian on section 5
\\ ( , 953kb)
replaced with revised version Thu, 27 Dec 2007 01:09:33 GMT (110kb)

Title: Condensation phenomena with distinguishable particles
Authors: Jun Ohkubo
Categories: cond-mat.dis-nn cond-mat.stat-mech
Comments: 7 pages, 4 figures
Journal-ref: Phys. Rev. E. 76, 051108 (2007)
\\ ( , 110kb)
replaced with revised version Thu, 27 Dec 2007 07:52:55 GMT (175kb)

Title: Role of Particle Interactions in the Feshbach Conversion of Fermion
   Atoms to Bosonic Molecules
Authors: Jie Liu, Li-Bin Fu, Bin Liu, and Biao Wu
Categories: cond-mat.mes-hall
Comments: 5 pages, 4 figures
\\ ( , 175kb)

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 Jan 07 2008 - 09:33:23 EST

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