Matt's arXiv selection, Monday 10 April 2006.

From: Matthew Davis <>
Date: Mon, 10 Apr 2006 10:48:18 +1000 (EST)

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

Lots of papers again this week. Matt's arXiv home page is here:

Next week's email may be a day late due to Easter Monday being a holiday!


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
Paper: cond-mat/0603838
Date: Fri, 31 Mar 2006 06:21:15 GMT   (789kb)
Title: Modulation instability and solitary wave formation in two-component
   Bose-Einstein condensates
Authors: Kenichi Kasamatsu, Makoto Tsubota
Comments: 16 pages, 13 figures
Subj-class: Other
   We investigate nonlinear dynamics induced by the modulation instability of a
two-component mixture in an atomic Bose-Einstein condensate. The nonlinear
dynamics is examined using numerical simulations of the time-dependent coupled
Gross-Pitaevskii equations. The unstable modulation grows from initially
miscible condensates into various types of vector solitary waves, depending on
the combinations of the sign of the coupling constants (intracomponent and
intercomponent). We discuss the detailed features of the modulation
instability, dynamics of solitary wave formation, and an analogy with the
collapsing dynamics in a single-component condensate with attractive
\\ ( ,  789kb)
Paper: cond-mat/0603857
Date: Fri, 31 Mar 2006 13:57:49 GMT   (470kb)
Title: Defect modes of a Bose-Einstein condensate in an optical lattice with a
   localized impurity
Authors: V.A. Brazhnyi, V.V. Konotop, V.M. P\'erez-Garc\'{\i}a
Comments: 14 pages, 9 Figures, 1 Table
Subj-class: Soft Condensed Matter
   We study defect modes of a Bose-Einstein condensate in an optical lattice
with a localized defect within the framework of the one-dimensional
Gross-Pitaevskii equation. It is shown that for a significant range of
parameters the defect modes can be accurately described by an expansion over
Wannier functions, whose envelope is governed by the coupled nonlinear
Schr\"{o}dinger equation with a delta-impurity. The stability of the defect
modes is verified by direct numerical simulations of the underlying
Gross-Pitaevskii equation with a periodic plus defect potentials. We also
discuss possibilities of driving defect modes through the lattice and suggest
ideas for their experimental generation.
\\ ( ,  470kb)
Paper: cond-mat/0603859
Date: Fri, 31 Mar 2006 18:09:07 GMT   (66kb)
Title: Ground state cooling of atoms in optical lattices
Authors: M. Popp, J. J. Garcia-Ripoll, K. G. H. Vollbrecht, J. I. Cirac
Comments: 12 pages, 7 figures
Subj-class: Statistical Mechanics
   We propose two schemes for cooling bosonic and fermionic atoms in an optical
lattice potential to the ground state of the Mott-insulating regime. The first,
algorithmic scheme is inspired by quantum computation. The second protocol is
based on the sequential application of occupation number filtering. We provide
a complete theoretical analysis of both schemes and predict the cooling
efficiency in terms of the entropy. Our schemes do not require addressing of
single lattice sites and use a novel method, which is based on coherent laser
control, to perform very fast filtering operations.
\\ ( ,  66kb)
Paper: cond-mat/0501510
replaced with revised version Fri, 31 Mar 2006 18:42:42 GMT   (31kb)
Title: Factorization in Break-up and Recombination Processes for Atoms with a
   Large Scattering Length
Authors: Eric Braaten and Dongqing Zhang
Comments: 7 pages, 3 figures
Subj-class: Other; Atomic and Molecular Clusters
\\ ( ,  31kb)
Paper: cond-mat/0507521
replaced with revised version Fri, 31 Mar 2006 16:07:52 GMT   (100kb)
Title: Dynamics of F=1 87Rb condensates at finite temperatures
Authors: Jordi Mur-Petit, Montserrat Guilleumas, Artur Polls, Anna Sanpera,
   Maciej Lewenstein, Kai Bongs, Klaus Sengstock
Comments: 6 pages + 5 figures; matches the published version (and corrects some
   typos there)
Subj-class: Mesoscopic Systems and Quantum Hall Effect
Journal-ref: Physical Review A 73, 013629 (2006)
DOI: 10.1103/PhysRevA.73.013629
\\ ( ,  100kb)
Paper: quant-ph/0603280
Date: Thu, 30 Mar 2006 23:22:09 GMT   (122kb)
Title: Many-body quantum dynamics of polarisation squeezing in optical fibre
Authors: J. F. Corney, P. D. Drummond, J. Heersink, V. Josse, G. Leuchs and U.
   L. Andersen
Comments: 4 pages, 4 figures
   We report new experiments that test quantum dynamical predictions of
polarization squeezing for ultrashort photonic pulses in a birefringent fibre,
including all relevant dissipative effects. This exponentially complex
many-body problem is solved by means of a stochastic phase-space method. The
squeezing is calculated and compared to experimental data, resulting in
excellent quantitative agreement. From the simulations, we identify the
physical limits to quantum noise reduction in optical fibres. The research
represents a significant experimental test of first-principles time-domain
quantum dynamics in a one-dimensional interacting Bose gas coupled to
dissipative reservoirs.
\\ ( ,  122kb)
Paper: physics/0603268
Date: Fri, 31 Mar 2006 15:42:14 GMT   (537kb)
Title: On the Role of Penning Ionization in Photoassociation Spectroscopy
Authors: E. van der Zwan, D. van Oosten, D. Nehari, P. van der Straten, and
   H.T.C. Stoof
Comments: 14 pages, 18 figures, submitted to the special issue on Cold
   Molecules of J. Phys. B
Subj-class: Atomic Physics
   We study the role of Penning ionization on the photoassociation spectra of
He(^3S)-He(^3S). The experimental setup is discussed and experimental results
for different intensities of the probe laser are shown. For modelling the
experimental results we consider coupled-channel calculations of the crossing
of the ground state with the excited state at the Condon point. The
coupled-channel calculations are first applied to model systems, where we
consider two coupled channels without ionization, two coupled channels with
ionization, and three coupled channels, for which only one of the excited
states is ionizing. Finally, coupled-channel calculations are applied to
photoassociation of He(^3S)-He(^3S) and good agreement is obtained between the
model and the experimental results.
\\ ( ,  537kb)
Paper: physics/0603263
Date: Thu, 30 Mar 2006 21:21:15 GMT   (5kb)
Title: Intelligent Design in the Physics Classroom?
Authors: Travis Norsen
Subj-class: Popular Physics; History of Physics
   This fun polemical piece was written several months ago on a tip that the
\emph{Chronicle of Higher Education} might be interested in publishing
something like it. Sadly (both for me and, I think, for the \emph{Chronicle}'s
readership) the editors didn't think it was of sufficient interest to the wider
academic community. I am posting it here at the arxiv so that it can,
nevertheless, be publicly available. If anyone out there wants to (suggest a
place to) publish the piece, I'm all ears.
\\ ( ,  5kb)
Paper: cond-mat/0604005
Date: Fri, 31 Mar 2006 22:39:33 GMT   (35kb)
Title: The relation between Feynman cycles and off-diagonal long-range order
Authors: Daniel Ueltschi
Comments: 4 pages
Subj-class: Statistical Mechanics
   The usual order parameter for the Bose-Einstein condensation involves the
off-diagonal correlation function of Penrose and Onsager, but an alternative is
Feynman's notion of infinite cycles. We present a formula that relates both
order parameters. We discuss its validity with the help of rigorous results and
heuristic arguments. The conclusion is that infinite cycles do not always
represent the Bose condensate.
\\ ( ,  35kb)
Paper: cond-mat/0604006
Date: Fri, 31 Mar 2006 23:12:16 GMT   (63kb)
Title: Stability of fermionic Feshbach molecules in a Bose-Fermi mixture
Authors: Alexander V. Avdeenkov, Daniele C. E. Bortolotti, John.L.Bohn
Subj-class: Statistical Mechanics
   In the wake of successful experiments in Fermi condensates, experimental
attention is broadening to study resonant interactions in degenerate Bose-Fermi
mixtures. Here we consider the properties and stability of the fermionic
molecules that can be created in such a mixture near a Feshbach resonance (FR).
To do this, we consider the two-body scattering matrix in the many-body
environment, and assess its complex poles. The stability properties of these
molecules strongly depend on their centre-of-mass motion, because they must
satisfy Fermi statistics. At low centre-of-mass momenta the molecules are more
stable than in the absence of the environment (due to Pauli-blocking effects),
while at high centre-of-mass momenta nontrivial many body effects render them
somewhat less stable.
\\ ( ,  63kb)
Paper: cond-mat/0604009
Date: Sat, 1 Apr 2006 07:00:04 GMT   (394kb)
Title: Bending-wave Instability of a Vortex Ring in a Trapped Bose-Einstein
Authors: T.-L. Horng, S.-C. Gou, T.-C. Lin
Comments: 4 pages, 4 figures
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   Based on a velocity formula derived by matched asymptotic expansion, we
investigate the dynamics of a circular vortex ring in an axisymmetric
Bose-Einstein condensate in the Thomas-Fermi limit. The trajectory for an
axisymmetrically placed and oriented vortex ring is entirely determined,
revealing that the vortex ring generally precesses in condensate. The linear
instability due to bending waves is investigated both numerically and
analytically. General stability boundaries for various perturbed wavenumbers
are computed. In particular, the excitation spectrum and the absolutely stable
region for the static ring are analytically determined.
\\ ( ,  394kb)
Paper: cond-mat/0604035
Date: Mon, 3 Apr 2006 13:17:02 GMT   (25kb)
Title: Pair-correlation in Bose-Einstein Condensate and Fermi Superfluid of
   Atomic Gases
Authors: Bimalendu Deb
Comments: 11 pages, 3 figures, based on the lecture delivered at TC-2005, held
   at IACS, Kolkata
Subj-class: Superconductivity
   We describe pair-correlation inherent in the structure of many-particle
ground state of quantum gases, namely, Bose Einstein condensate and
Cooper-paired Fermi superfluid of atomic gases. We make a comparative study on
the pair-correlation properties of these two systems. We discuss how to probe
this pair-correlation by stimulated light scattering. This intrinsic
pair-correlation may serve as a resource for many-particle entanglement.
\\ ( ,  25kb)
Paper: cond-mat/0604038
Date: Mon, 3 Apr 2006 11:46:49 GMT   (909kb)
Title: Precision measurement of spin-dependent interaction strengths for spin-1
   and spin-2 87Rb atoms
Authors: Artur Widera, Fabrice Gerbier, Simon Foelling, Tatjana Gericke, Olaf
   Mandel, Immanuel Bloch
Comments: 11 pages, 5 figures
Subj-class: Other
   We report on precision measurements of spin-dependent interaction-strengths
in the 87Rb spin-1 and spin-2 hyperfine ground states. Our method is based on
the recent observation of coherence in the collisionally driven spin-dynamics
of ultracold atom pairs trapped in optical lattices. Analysis of the Rabi-type
oscillations between two spin states of an atom pair allows a direct
determination of the coupling parameters in the interaction hamiltonian. We
deduce differences in scattering lengths from our data that can directly be
compared to theoretical predictions in order to test interatomic potentials.
Our measurements agree with the predictions within 20%. The knowledge of these
coupling parameters allows one to determine the nature of the magnetic ground
state. Our data imply a ferromagnetic ground state for 87Rb in the f=1
manifold, in agreement with earlier experiments performed without the optical
lattice. For 87Rb in the f=2 manifold the data points towards an
antiferromagnetic ground state, however our error bars do not exclude a
possible cyclic phase.
\\ ( ,  909kb)
Paper: cond-mat/0604063
Date: Mon, 3 Apr 2006 19:30:37 GMT   (12kb)
Title: Disorder-Induced Order: From Classical Spin Systems to Ultracold Atomic
Authors: Jan Wehr, Armand Niederberger, Laurent Sanchez-Palencia (LCFIO),
   Maciej Lewenstein (ITP-HANNOVER)
Proxy: ccsd ccsd-00022177
Subj-class: Other
   We propose a general mechanism of disorder-induced order by studying a
particular case of classical ferromagnetic XY model in a random uniaxial field
which breaks the continuous symmetry of the model. We prove rigorously that the
system has spontaneous magnetization at temperature T=0, and we present strong
evidence that this is also the case for small T>0. We discuss generalizations
of this mechanism to various classical spin models and quantum systems. We
propose a realization of this phenomenon with ultracold atoms in an optical
\\ ( ,  12kb)
Paper: quant-ph/0603218
Date: Thu, 23 Mar 2006 19:05:47 GMT   (214kb)
Title: A Stern-Gerlach experiment for slow light
Authors: Leon Karpa and Martin Weitz
Comments: 11 pages, 3 figures. Nature Physics, in press
Subj-class: Quantum Physics; Atomic Physics; Soft Condensed Matter
   Electromagnetically induced transparency allows for light transmission
through dense atomic media by means of quantum interference. Media exhibiting
electromagnetically induced transparency have very interesting properties, such
as extremely slow group velocities. Associated with the slow light propagation
are quasiparticles, the so-called dark polaritons, which are mixtures of a
photonic and an atomic contribution. We here demonstrate that these excitations
behave as particles with a nonzero magnetic moment, which is in clear contrast
to the properties of a free photon. It is found that light passing through a
rubidium gas cell under the conditions of electromagnetically induced
transparency is deflected by a small magnetic field gradient. The deflection
angle is proportional to the optical propagation time through the cell. The
observed beam deflection can be understood by assuming that dark state
polaritons have an effective magnetic moment. Our experiment can be described
in terms of a Stern-Gerlach experiment for the polaritons.
\\ ( ,  214kb)
Paper: cond-mat/0506210
replaced with revised version Mon, 3 Apr 2006 15:18:34 GMT   (61kb)
Title: Shock waves in a one-dimensional Bose gas: from a Bose-Einstein
   condensate to a Tonks gas
Authors: Bogdan Damski
Comments: 10 pages, small corrections with respect to the last submission,
   version accepted in Phys. Rev. A
Report-no: LAUR-05-4188
Subj-class: Other; Pattern Formation and Solitons; Quantum Physics
Journal-ref: Phys. Rev. A 73, 043601 (2006)
\\ ( ,  61kb)
Paper: cond-mat/0601392
replaced with revised version Mon, 3 Apr 2006 13:25:02 GMT   (533kb)
Title: Noise Thermometry with Two Weakly Coupled Bose-Einstein Condensates
Authors: Rudolf Gati, Boerge Hemmerling, Jonas Foelling, Michael Albiez, Markus
   K. Oberthaler
Comments: 4 pages, 4 figures
Subj-class: Other
\\ ( ,  533kb)
Paper: cond-mat/0602616
replaced with revised version Mon, 3 Apr 2006 08:11:16 GMT   (93kb)
Title: Commensurate mixtures of ultra-cold atoms in one dimension
Authors: L. Mathey
Comments: 4 pages, 2 figures, v2: a few minor changes
Subj-class: Other
\\ ( ,  93kb)
Paper: cond-mat/0603340
replaced with revised version Mon, 3 Apr 2006 15:17:31 GMT   (25kb)
Title: Calogero-Sutherland gas of ultracold Bose atoms
Authors: Yue Yu
Comments: 4 pages,1 figure,update version
Subj-class: Other; Statistical Mechanics
\\ ( ,  25kb)
Paper: quant-ph/0604006
Date: Sun, 2 Apr 2006 13:19:58 GMT   (322kb)
Title: Regimes of stability of accelerator modes
Authors: Rebecca Hihinashvili, Tali Oliker, Yaniv S. Avizrats, Alexander Iomin,
   Shmuel Fishman, Italo Guarneri
Comments: Submitted to Physica D
   The phase diagram of a simple area-preserving map, which was motivated by the
quantum dynamics of cold atoms, is explored analytically and numerically.
Periodic orbits of a given winding ratio are found to exist within wedge-shaped
regions in the phase diagrams, which are analogous to the Arnol'd tongues which
have been extensively studied for a variety of dynamical systems, mostly
dissipative ones. A rich variety of bifurcations of various types are observed,
as well as period doubling cascades. Stability of periodic orbits is analyzed
in detail.
\\ ( ,  322kb)
Paper: cond-mat/0604086
Date: Tue, 4 Apr 2006 13:20:34 GMT   (307kb)
Title: Bright Matter-Wave Soliton Collisions in a Harmonic Trap: Regular and
   Chaotic Dynamics
Authors: A. D. Martin, S. A. Gardiner and C. S. Adams
Comments: 4 pages, 2 figures
Subj-class: Other
   Collisions between bright solitary waves in the 1D Gross-Pitaevskii equation
with a harmonic potential, which models a trapped atomic Bose-Einstein
condensate, are investigated theoretically. A particle analogy for the solitary
waves is formulated, which is shown to be integrable for a two-particle system.
The extension to three particles is shown to support chaotic regimes. Good
agreement is found between the particle model and simulations of the full wave
dynamics, suggesting that the dynamics can be described in terms of solitons
both in regular and chaotic regimes, thus presenting a paradigm for chaos in
\\ ( ,  307kb)
Paper: cond-mat/0604095
Date: Tue, 4 Apr 2006 15:48:32 GMT   (151kb)
Title: Tuning the Mott transition in a Bose-Einstein condensate by multi-photon
Authors: C.E. Creffield and T.S. Monteiro
Comments: 5 pages, 4 eps figures
Subj-class: Other
   We study the time-dependent dynamics of a Bose-Einstein condensate trapped in
an optical lattice. Modeling the system as a Bose-Hubbard model, we show how
applying a periodic driving field can induce coherent destruction of tunneling.
In the low-frequency regime, we obtain the novel result that the destruction of
tunneling displays extremely sharp peaks when the driving frequency is resonant
with the depth of the trapping potential (``multi-photon resonances''), which
allows the quantum phase transition between the Mott insulator and the
superfluid state to be controlled with high precision. We further show how the
waveform of the field can be chosen to maximize this effect.
\\ ( ,  151kb)
Paper: cond-mat/0509263
replaced with revised version Tue, 4 Apr 2006 12:41:06 GMT   (659kb)
Title: Vortex Tunneling and Transport Theory In Two-Dimensional Bose
Authors: Assa Auerbach (Technion), Daniel P. Arovas (UCSD), and Sankalpa Ghosh
Comments: A revised manuscript, including new predictions for observing vortex
   tunneling effects in cold atoms and superconducting films
Subj-class: Superconductivity; Strongly Correlated Electrons
\\ ( ,  659kb)
Paper: cond-mat/0604115
Date: Wed, 5 Apr 2006 04:20:46 GMT   (55kb)
Title: Conditions of Low Dimensionality for Strongly Interacting Atoms Under a
   Transverse Trap
Authors: J. P. Kestner, L.-M. Duan
Comments: 9 pages, 7 figures
Subj-class: Other
   For a dilute atomic gas in a strong transverse trapping potential, one
normally expects that, in the ground state, the gas will populate only the
lowest transverse level. We show, however, that for the strongly interacting
gas under a Feshbach resonance, the ground state includes a large fraction of
atoms in excited levels of the trap, even if the gas is very dilute and the
trap is very strong. This is because the effective atom-molecule coupling is
typically enhanced to many times the trap mode spacing by an induced
confinement along the untrapped dimension(s). Thus one cannot ''freeze out''
the transverse degrees of freedom except under certain conditions.
\\ ( ,  55kb)
Paper: cond-mat/0604139
Date: Wed, 5 Apr 2006 16:31:57 GMT   (599kb)
Title: Bose-Fermi Mixtures in a Three-dimensional Optical Lattice
Authors: Kenneth G\"unter, Thilo St\"oferle, Henning Moritz, Michael K\"ohl,
   Tilman Esslinger
Subj-class: Strongly Correlated Electrons
   We have studied mixtures of fermionic $^{40}$K and bosonic $^{87}$Rb quantum
gases in a three-dimensional optical lattice. We observe that an increasing
admixture of the fermionic species diminishes the phase coherence of the
bosonic atoms as measured by studying both the visibility of the matter wave
interference pattern and the coherence length of the bosons. Moreover, we find
that the attractive interactions between bosons and fermions lead to an
increase of the boson density in the lattice which we measure by studying
three-body recombination in the lattice. In our data we do not observe
three-body loss of the fermionic atoms. An analysis of the thermodynamics of a
noninteracting Bose-Fermi mixture in the lattice suggests a mechanism for
sympathetic cooling of the fermions in the lattice.
\\ ( ,  599kb)
Paper: cond-mat/0603699
replaced with revised version Wed, 5 Apr 2006 02:52:16 GMT   (908kb)
Title: Vortex creation during magnetic trap manipulations of spinor
   Bose-Einstein condensates
Authors: A.P. Itin, T. Morishita, M. Satoh, O.I. Tolstikhin, and S. Watanabe
Comments: 16 pages, 8 figures (of reduced quality; original figures are
   available upon request:; Comments to ver.2: calculations
   without gravity were added, several typos corrected
Subj-class: Other
\\ ( ,  908kb)
Paper (*cross-listing*): math.DS/0405112
replaced with revised version Wed, 5 Apr 2006 18:45:15 GMT   (543kb)
Title: Quasiperiodic Dynamics in Bose-Einstein Condensates in Periodic Lattices
   and Superlattices
Authors: Martijn van Noort, Mason A. Porter, Yingfei Yi, and Shui-Nee Chow
Comments: 29 pages, 6 figures (several with multiple parts; higher-quality
   versions of some of them available at, submitted to Journal of Nonlinear
   Science, revised version includes additional discussion of physics and an
   additional conclusions/discussion section; some other revisions are sprinkled
   throughout the text
Subj-class: Dynamical Systems; Chaotic Dynamics; Soft Condensed Matter; Atomic
MSC-class: MSC: 37J40, 70H99, 37N20; PACS: 05.45.-a, 03.75.Lm, 05.30.Jp,
   05.45.Ac, 03.75.Nt
\\ ( ,  543kb)
Paper: quant-ph/0604022
Date: Wed, 5 Apr 2006 13:26:39 GMT   (224kb)
Title: Vibration induced phase noise in Mach-Zehnder atom interferometers
Authors: Alain Miffre (LCAR, PIIM), Marion Jacquey (LCAR), Matthias B\"{u}chner
   (LCAR), G\'{e}rard Tr\'{e}nec (LCAR), Jacques Vigu\'{e} (LCAR)
Proxy: ccsd ccsd-00022231
   The high inertial sensitivity of atom interferometers has been used to build
accelerometers and gyrometers but this sensitivity makes these interferometers
very sensitive to the laboratory seismic noise. This seismic noise induces a
phase noise which is large enough to reduce the fringe visibility in many
cases. We develop here a model calculation of this phase noise in the case of
Mach-Zehnder atom interferometers and we apply this model to our thermal
lithium interferometer. We are thus able to explain the observed dependence of
the fringe visibility with the diffraction order. The dynamical model developed
in the present paper should be very useful to further reduce this phase noise
in atom interferometers and this reduction should open the way to improved
\\ ( ,  224kb)
Paper: quant-ph/0604028
Date: Wed, 5 Apr 2006 18:59:26 GMT   (103kb)
Title: Phase noise due to vibrations in Mach-Zehnder atom interferometers
Authors: A. Miffre (LCAR, Piim), M. Jacquey (LCAR), M. B\"{u}chner (LCAR), G.
   Tr\'{e}nec (LCAR), J. Vigu\'{e} (LCAR)
Proxy: ccsd ccsd-00022285
   Atom interferometers are very sensitive to accelerations and rotations. This
property, which has some very interesting applications, induces a deleterious
phase noise due to the seismic noise of the laboratory and this phase noise is
sufficiently large to reduce the fringe visibility in many experiments. We
develop a model calculation of this phase noise in the case of Mach-Zehnder
atom interferometers and we apply this model to our thermal lithium
interferometer. We are able to explain the observed phase noise which has been
detected through the rapid dependence of the fringe visibility with the
diffraction order. We think that the dynamical model developed in the present
paper should be very useful to reduce the vibration induced phase noise in atom
interferometers, making many new experiments feasible.
\\ ( ,  103kb)
Paper: physics/0604026
Date: Wed, 5 Apr 2006 02:24:36 GMT   (244kb)
Title: Sub-natural resonances due to ground state coherence in 6Li
Authors: J. Fuchs, G. J. Duffy, W. J. Rowlands and A. M. Akulshin
Comments: 13 pages, 10 figures
Subj-class: Atomic Physics
   We report sub-Doppler and sub-natural linewidth spectroscopy of 6Li on the D1
and D2 lines in both a vapour cell and an atomic beam. Electromagnetically
induced transparency is created using co-propagating mutually coherent laser
beams with a frequency difference equal to the hyperfine ground state splitting
of 228.2 MHz. The effects of various optical polarization configurations and
applied magnetic fields are investigated. In addition, we present an optical
Ramsey spectroscopy technique which further reduces the observed resonance
\\ ( ,  244kb)
Paper (*cross-listing*): math.DS/0405112
replaced with revised version Wed, 5 Apr 2006 18:45:15 GMT   (543kb)
Title: Quasiperiodic Dynamics in Bose-Einstein Condensates in Periodic Lattices
   and Superlattices
Authors: Martijn van Noort, Mason A. Porter, Yingfei Yi, and Shui-Nee Chow
Comments: 29 pages, 6 figures (several with multiple parts; higher-quality
   versions of some of them available at, submitted to Journal of Nonlinear
   Science, revised version includes additional discussion of physics and an
   additional conclusions/discussion section; some other revisions are sprinkled
   throughout the text
Subj-class: Dynamical Systems; Chaotic Dynamics; Soft Condensed Matter; Atomic
MSC-class: MSC: 37J40, 70H99, 37N20; PACS: 05.45.-a, 03.75.Lm, 05.30.Jp,
   05.45.Ac, 03.75.Nt
\\ ( ,  543kb)
Paper: cond-mat/0604147
Date: Wed, 5 Apr 2006 21:22:48 GMT   (221kb)
Title: Skyrmion-like excitations in dynamical lattices
Authors: P. G. Kevrekidis, R. Carretero-Gonzalez, D. J. Frantzeskakis, B. A.
   Malomed, and F. K. Diakonos
Comments: 4 pages, 5 figures
Subj-class: Other
   We construct discrete analogs of Skyrmions in nonlinear dynamical lattices.
The Skyrmion is built as a vortex soliton of a complex field, coupled to a dark
radial soliton of a real field. Adjusting the Skyrmion ansatz to the lattice
setting allows us to construct a ``baby-Skyrmion'' in two dimensions (2D) and
extend it into the 3D case (1D counterparts of the Skyrmions are also found).
Stability limits for these patterns are obtained analytically and verified
numerically. The dynamics of unstable discrete Skyrmions is explored, and their
stabilization by external potentials is discussed.
\\ ( ,  221kb)
Paper: cond-mat/0604149
Date: Wed, 5 Apr 2006 23:47:27 GMT   (139kb)
Title: BCS-BEC Crossover in Atomic Fermi Gases with a Narrow Resonance
Authors: L. M. Jensen, H. M. Nilsen, and Gentaro Watanabe
Comments: 12 pages, 14 figures
Report-no: NORDITA-2006-10
Subj-class: Superconductivity; Strongly Correlated Electrons
   We determine the effects on the BCS-BEC crossover of the energy dependence of
the effective two-body interaction, which at low energies is determined by the
effective range. To describe interactions with an effective range of either
sign, we consider a single-channel model with a two-body interaction having an
attractive square well and a repulsive square barrier. We investigate the
two-body scattering properties of the model, and then solve the Eagles-Leggett
equations for the zero temperature crossover, determining the momentum
dependent gap and the chemical potential self-consistently. From this we
investigate the dependence of the crossover on the effective range of the
\\ ( ,  139kb)
Paper: cond-mat/0604151
Date: Thu, 6 Apr 2006 01:58:01 GMT   (155kb)
Title: Instabilities leading to vortex lattice formation in rotating
   Bose-Einstein condensates
Authors: N. G. Parker, R. M. W. van Bijnen, and A. M. Martin
Comments: 5 pages, 2 figures
Subj-class: Other
   We present a comprehensive theoretical study of vortex lattice formation in
atomic Bose-Einstein condensates confined by a rotating elliptical trap. We
consider rotating solutions of the classical hydrodynamic equations, their
response to perturbations, as well as time-dependent simulations. We
discriminate three distinct, experimentally testable, regimes of instability:
{\em ripple}, {\em interbranch}, and {\em catastrophic}. Under
symmetry-breaking perturbations these instabilities lead to lattice formation
even at zero temperature. While our results are consistent with previous
theoretical and experimental results, they shed new light on lattice formation.
\\ ( ,  155kb)
Paper: cond-mat/0604154
Date: Thu, 6 Apr 2006 03:00:21 GMT   (888kb)
Title: Hanbury Brown-Twiss Interferometry for Fractional and Integer Mott
Authors: Ana Maria Rey, Indubala I. Satija and Charles W. Clark
Comments: 13 pages, 15 figures
Subj-class: Soft Condensed Matter; Other
   Hanbury-Brown-Twiss interferometry (HBTI) is used to study integer and
fractionally filled Mott Insulator (MI) phases in period-2 optical
superlattices. In contrast to the quasimomentum distribution, this second order
interferometry pattern exhibits high contrast fringes in the it insulating
phases. Our detailed study of HBTI suggests that this interference pattern
signals the various superfluid-insulator transitions and therefore can be used
as a practical method to determine the phase diagram of the system. We find
that in the presence of a confining potential the insulating phases become
robust as they exist for a finite range of atom numbers. Furthermore, we show
that in the trapped case the HBTI interferogram signals the formation of the MI
domains and probes the shell structure of the system.
\\ ( ,  888kb)
Paper: cond-mat/0604162
Date: Thu, 6 Apr 2006 08:52:33 GMT   (32kb)
Title: Thermodynamical Properties of a Rotating Ideal Bose Gas
Authors: Sebastian Kling, Axel Pelster
Comments: Author Information under
Subj-class: Statistical Mechanics
   In a recent experiment, a Bose-Einstein condensate was trapped in an
anharmonic potential which is well approximated by a harmonic and a quartic
part. The condensate was set into such a fast rotation that the centrifugal
force in the corotating frame overcompensates the harmonic part in the plane
perpendicular to the rotation axis. Thus, the resulting trap potential became
Mexican-hat shaped. We present an analysis for an ideal Bose gas which is
confined in such an anharmonic rotating trap within a semiclassical
approximation where we calculate the critical temperature, the condensate
fraction, and the heat capacity. In particular, we examine in detail how these
thermodynamical quantities depend on the rotation frequency.
\\ ( ,  32kb)
Paper: cond-mat/0604164
Date: Thu, 6 Apr 2006 08:57:59 GMT   (37kb)
Title: Fragmented condensates due to frustration of cold atoms in optical
Authors: J. J. Garcia-Ripoll, J. Pachos
Subj-class: Strongly Correlated Electrons
   A one dimensional optical lattice is considered where a second dimension is
encoded in the internal states of the atoms giving effective ladder systems.
Frustration is introduced by an additional optical lattice that induces
tunnelling of superposed states. The effects of frustration range from the
stabilization of the Mott insulator phase with ferromagnetic order, to the
breakdown of superfluidity and the formation of fragmented condensates that
resemble a Bose glass phase.
\\ ( ,  37kb)
Paper: cond-mat/0604170
Date: Thu, 6 Apr 2006 13:15:36 GMT   (78kb)
Title: Equilibration problem for the generalized Langevin equation
Authors: Abhishek Dhar and Kshitij Wagh
Comments: 4 pages, 1 figure
Subj-class: Statistical Mechanics
   We consider the problem of equilibration of a single oscillator system with
dynamics given by the generalized Langevin equation. It is well-known that this
dynamics can be obtained if one considers a model where the single oscillator
is coupled to an infinite bath of harmonic oscillators which are initially in
equilibrium. Using this equivalence we first determine the conditions necessary
for equilibration for the case when the system potential is harmonic. We then
give an example with a particular bath where we show that, even for parameter
values where the harmonic case always equilibrates, with any finite amount of
nonlinearity the system does not equilibrate for arbitrary initial conditions.
We understand this as a consequence of the formation of nonlinear localized
excitations similar to the discrete breather modes in nonlinear lattices.
\\ ( ,  78kb)
Paper: cond-mat/0604179
Date: Thu, 6 Apr 2006 17:55:00 GMT   (323kb)
Title: Localization of bosonic atoms by fermionic impurities in a 3d optical
Authors: S. Ospelkaus, C. Ospelkaus, O. Wille, M. Succo, P. Ernst, K. Sengstock
   and K. Bongs
Comments: 4 pages, 4 figures
Subj-class: Statistical Mechanics; Strongly Correlated Electrons
   We observe a localized phase of ultracold bosonic quantum gases in a
3-dimensional optical lattice induced by a small contribution of fermionic
atoms acting as impurities in a Fermi-Bose quantum gas mixture. In particular
we study the dependence of this transition on the fermionic 40K impurity
concentration by a comparison to the corresponding superfluid to Mott insulator
transition in a pure bosonic 87Rb gas and find a significant shift in the
transition parameter. The observed shift is larger than expected based on a
mean-field argument, which is a strong indication that disorder-related effects
play a significant role.
\\ ( ,  323kb)
Paper: cond-mat/0604183
Date: Thu, 6 Apr 2006 18:59:13 GMT   (26kb)
Title: Collisional relaxation of Feshbach molecules and three-body
   recombination in 87Rb Bose-Einstein condensates
Authors: G. Smirne, R. M. Godun, D. Cassettari, V. Boyer, C. J. Foot, T. Volz,
   N. Syassen, S. Duerr, G. Rempe, M. D. Lee, K. Goral, T. Koehler
Comments: 4 pages, 3 eps figures
Subj-class: Other
   We determine the magnetic field dependence of three-body recombination and
atom-dimer collision rates in a 87Rb Bose-Einstein condensate (BEC) close to
1007 G. Our exact treatments of three-particle scattering explicitly include
the dependence of the interactions on the Zeeman levels of each atom. The
weakly coupled Feshbach resonance distorts the entire diatomic energy spectrum
causing interferences in both loss phenomena. Our two independent experiments
confirm the predicted resonance-enhanced recombination loss over a range of
rate constants that spans four orders of magnitude.
\\ ( ,  26kb)
Paper: cond-mat/0604184
Date: Thu, 6 Apr 2006 19:11:37 GMT   (43kb)
Title: Two-species fermion mixtures with population imbalance
Authors: M. Iskin and C. A. R. Sa de Melo
Comments: 4 pages with 4 figures
Subj-class: Superconductivity; Other
   We analyze the phase diagram of uniform superfluidity for two-species fermion
mixtures from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation
(BEC) limit as a function of the scattering parameter and population imbalance.
We find at zero temperature that the phase diagram of population imbalance
versus scattering parameter is asymmetric for non-equal masses, having a larger
stability region for uniform superfluidity when the lighter fermions are in
excess. In addition, we find topological quantum phase transitions associated
with the disappearance or appearance of momentum space regions of zero
quasiparticle energies. Lastly, near the critical temperature, we derive the
Ginzburg-Landau equation, and show that it describes a dilute mixture of
composite bosons and unpaired fermions in the BEC limit.
\\ ( ,  43kb)
Paper: cond-mat/0603513
replaced with revised version Thu, 6 Apr 2006 09:16:52 GMT   (67kb)
Title: Ultra Cold Atoms in Incommensurate 1D Optical Lattices - an Interacting
   Aubry-Andre Model
Authors: Nir Bar-Gill, Rami Pugatch, Eitan Rowen, Nadav Katz, and Nir Davidson
Comments: 5 pages, 4 figures
Subj-class: Disordered Systems and Neural Networks
\\ ( ,  67kb)
Paper: quant-ph/0604032
Date: Wed, 5 Apr 2006 20:22:08 GMT   (59kb)
Title: Excited state contribution to the Casimir-Polder force at finite
Authors: T.N.C.Mendes and C. Farina
Comments: 3 pages, 3 figures
   Using the master equation we calculate the contribution of the excited state
of a two-level atom to its interacting potential with a perfectly conducting
wall at finite temperature. For low temperature, $\hbar \omega_0/k_B T = k_0
\lambda_T\gg 1$, where $\omega_0 = k_0 c$ is the transition frequency of the
atom and $\lambda_T$ is the thermal wavelength, we show that this contribution
is very small $(\propto e^{-k_0\lambda_T})$. In the opposite limit
$(k_0\lambda_T \ll 1)$, however, we show that the expression for the
interacting potential, for all relevant distance regimes, becomes exactly the
same as that for very short distances $(k_0 z \ll 1)$ and with the field in the
vacuum state.
\\ ( ,  59kb)
Paper: quant-ph/0604033
Date: Wed, 5 Apr 2006 20:54:11 GMT   (125kb)
Title: Casimir-Polder forces from density matrix formalism
Authors: T.N.C. Mendes and C. Farina
Comments: 11 pages, 3 figures
   We use the density matrix formalism in order to calculate the energy level
shifts, in second order on interaction, of an atom in the presence of a
perfectly conducting wall in the dipole approximation. The thermal corrections
are also examined when $\hbar \omega_0/k_B T = k_0 \lambda_T \gg 1$, where
${$\omega_0=k_0 c$}$ is the dominant transition frequency of the atom and
$\lambda_T$ is the thermal length. When the distance $z$ between the atom and
the wall is larger than $\lambda_T$ we find the well known result obtained from
Lifshitz's formula, whose leading term is proportional to temperature and is
independent of $c$, $\hbar$ and $k_0$. In the short distance limit, when
$z\ll\lambda_T$, only very small corrections to the leading vacuum term occur.
We also show, for all distance regimes, that the main thermal corrections are
independent of $k_0$ (dispersion is not important) and dependent of $c$, which
means that there is not a non-retarded regime for the thermal contributions.
\\ ( ,  125kb)
Paper: quant-ph/0604034
Date: Wed, 5 Apr 2006 21:06:01 GMT   (12kb)
Title: A master equation approach for the interaction of an atom with a
   dielectric semi-infinite medium
Authors: T.N.C. Mendes and C. Farina
Comments: 9 pages
   We use the master equation approach to calculate the energy level shifts of
an atom in the presence of a general dielectric semi-infinite medium
characterized by a dielectric constant $\epsilon(\omega)$. Particularly, we
analyze the case of a non-dispersive medium for which we obtain a general
expression for the interaction as well as the asymptotic behaviors for $k_0 z
\ll 1$ (non-retarded regime) and $k_0 z \gg 1$ (retarded regime), where
$\omega_0 = k_0 c$ is the main transition frequency of the atom. The limiting
cases $\epsilon \simeq 1$ and $\epsilon \gg 1$ are discussed for both retarded
and non-retarded limits. For the retarded limit, we compute the non-additivity
contribution of van der Waals forces.
\\ ( ,  12kb)
Paper: quant-ph/0604037
Date: Thu, 6 Apr 2006 18:20:33 GMT   (136kb)
Title: Optimal Storage of Photon States in Optically Dense Atomic Media
Authors: Alexey V. Gorshkov, Axel Andre, Michael Fleischhauer, Anders S.
   Sorensen, Mikhail D. Lukin
Comments: 4 pages, 3 figures
   We derive an optimal control strategy for storage and retrieval of a photon
wavepacket of any given shape in a Lambda-type atomic medium with a limited
optical depth. The control is provided by an appropriately shaped classical
laser field. We present a universal physical picture encompassing different
pulse-storage techniques ranging from adiabatic reduction of the photon group
velocity and pulse-propagation control via off-resonant Raman fields to
photon-echo based approaches. When properly optimized, all three approaches
yield identical maximum efficiencies, which only depend on the optical depth of
the medium. Extending the model to include Doppler broadening, we find the
surprising result that at high enough optical depth all atoms contribute
coherently as if the medium were homogeneously broadened.
\\ ( ,  136kb)
Paper: quant-ph/0604040
Date: Thu, 6 Apr 2006 09:36:48 GMT   (85kb)
Title: Gain narrowing in few-atom systems
Authors: Tom Savels, Allard P. Mosk and Ad Lagendijk
   Using a density matrix approach, we study the simplest systems that display
both gain and feedback: clusters of 2 to 5 atoms, one of which is pumped. The
other atoms supply feedback through multiple scattering of light. We show that,
if the atoms are in each other's near-field, the system exhibits large gain
narrowing and spectral mode redistribution. The observed phenomena are more
pronounced if the feedback is enhanced. Our system is to our knowledge the
simplest exactly solvable microscopic system which shows the approach to laser
\\ ( ,  85kb)
Paper: quant-ph/0604043
Date: Thu, 6 Apr 2006 13:14:10 GMT   (554kb)
Title: Coherent imaging of a pure phase object with classical incoherent light
Authors: M. Bache, D. Magatti, A. Gatti, E. Brambilla, F. Ferri, and L.A.
Comments: 13 pages, 11 figures. To appear in Physical Review A
   By using the ghost imaging technique, we experimentally demonstrate the
reconstruction of the diffraction pattern of a {\em pure phase} object by using
the classical correlation of incoherent thermal light split on a beam splitter.
The results once again underline that entanglement is not a necessary feature
of ghost imaging. The light we use is spatially highly incoherent with respect
to the object ($\approx 2 \mu$m speckle size) and is produced by a
pseudo-thermal source relying on the principle of near-field scattering. We
show that in these conditions no information on the phase object can be
retrieved by only measuring the light that passed through it, neither in a
direct measurement nor in a Hanbury Brown-Twiss (HBT) scheme. In general, we
show a remarkable complementarity between ghost imaging and the HBT scheme when
dealing with a phase object.
\\ ( ,  554kb)
Received on Mon Apr 10 2006 - 10:48:18 EST

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