Matt's arXiv selection: week ending 14 November 2008

From: Matthew Davis <>
Date: Mon, 17 Nov 2008 10:01:53 +1000

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

Hi everyone,

This week there ar 31 new preprints and 11 replacements:

Date: Fri, 7 Nov 2008 00:57:40 GMT (159kb)

Title: Exact ground-state properties of interacting two-component Bose gases in
   a hard-wall trap
Authors: Yajiang Hao, Yunbo Zhang, Xi-Wen Guan, Shu Chen
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 7 pages, 8 figures
   We investigate ground-state properties of interacting two-component Bose
gases in a hard-wall trap using both the Bethe ansatz and exact numerical
diagonalization method. For equal intra- and inter-atomic interaction, the
system is exactly solvable. Thus the exact ground state wavefunction and
density distributions for the whole interacting regime can be obtained from the
Bethe ansatz solutions. Since the ground state is a degenerate state with total
spin S=N/2, the total density distribution are same for each degenerate state.
The total density distribution evolves from a Gauss-like Bose distribution to a
Fermi-like one as the repulsive interaction increases. The distribution of each
component is N_i/N of the total density distribution. This is approximately
true even in the experimental situation. In addition the numerical results show
that with the increase of interspecies interaction the distributions of two
Tonks-Girardeau gases exhibit composite fermionization crossover with each
component developing N peaks in the strongly interacting regime.
\\ ( , 159kb)
Date: Fri, 7 Nov 2008 13:00:07 GMT (271kb,D)

Title: Bose-Einstein condensates in a double well: mean-field chaos and
   multi-particle entanglement
Authors: Christoph Weiss, Niklas Teichmann
Categories: cond-mat.other
Comments: 5 Pages, 5 jpg-figures, to be published in the proceedings of the
   A recent publication [Phys. Rev. Lett. 100, 140408 (2008)] shows that there
is a relation between mean-field chaos and multi-particle entanglement for BECs
in a periodically shaken double well. 'Schrodinger-cat' like mesoscopic
superpositions in phase-space occur for conditions for which the system
displays mean-field chaos. In the present manuscript, more general
highly-entangled states are investigated. Mean-field chaos accelerates the
emergence of multi-particle entanglement; the boundaries of stable regions are
particularly suited for entanglement generation.
\\ ( , 271kb)
Date: Fri, 7 Nov 2008 15:42:31 GMT (86kb)

Title: Thermodynamic Measurements in a Strongly Interacting Fermi Gas
Authors: Le Luo and John E. Thomas
Categories: cond-mat.other
Comments: 29 pages, 12 figures. To appear in JLTP online, and in the January,
   2009 volume
   We conduct a series of measurements on the thermodynamic properties of an
optically-trapped strongly interacting Fermi gas, including the energy $E$,
entropy $S$, and sound velocity $c$. Our model-independent measurements of $E$
and $S$ enable a precision study of the finite temperature thermodynamics. The
$E(S)$ data are directly compared to several recent predictions. The
temperature in both the superfluid and normal fluid regime is obtained from the
fundamental thermodynamic relation $T=\partial E/\partial S$ by parameterizing
the $E(S)$ data. Our $E(S)$ data are also used to experimentally calibrate the
endpoint temperatures obtained for adiabatic sweeps of the magnetic field
between the ideal and strongly interacting regimes. This enables the first
experimental calibration of the temperature scale used in experiments on
fermionic pair condensation. Our calibration shows that the ideal gas
temperature measured for the onset of pair condensation corresponds closely to
the critical temperature estimated in the strongly interacting regime from the
fits to our $E(S)$ data. The results are in very good agreement with recent
predictions. Finally, using universal thermodynamic relations, we estimate the
chemical potential and heat capacity of the trapped gas from the $E(S)$ data.
\\ ( , 86kb)
Date: Fri, 7 Nov 2008 17:33:42 GMT (36kb)

Title: Quasiparticle excitations and dynamic susceptibilities in the BCS-BEC
Authors: J. Bauer and A.C. Hewson
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 6 pages, 5 figures
   We study dynamic ground state properties in the crossover from weak (BCS) to
strong coupling (BEC) superfluidity. Our approach is based on the attractive
Hubbard model which is analyzed by the dynamical mean field theory (DMFT)
combined with the numerical renormalization group (NRG). We present an
extension of the NRG method for effective impurity models to selfconsistent
calculations with superconducting symmetry breaking. In the one particle
spectra we show quantitatively how the Bogoliubov quasiparticles at weak
coupling become suppressed at intermediate coupling. We also present results
for the spin and charge gap. The extension of the NRG method to selfconsistent
superconducting solutions opens the possibility to study a range of other
important applications.
\\ ( , 36kb)
Date: Fri, 7 Nov 2008 14:49:25 GMT (581kb)

Title: Mesoscopic Rydberg Gate based on Electromagnetically Induced
Authors: M. M\"uller, I. Lesanovsky, H. Weimer, H. P. B\"uchler, and P. Zoller
Categories: quant-ph
   We demonstrate theoretically a parallelized C-NOT gate which allows to
entangle a mesoscopic ensemble of atoms with a single control atom in a single
step, with high fidelity and on a microsecond timescale. Our scheme relies on
the strong and long-ranged interaction between Rydberg atoms triggering
Electromagnetically Induced Transparency (EIT). By this we can robustly
implement a conditional transfer of all ensemble atoms among two logical
states, depending on the state of the control atom. We outline a many body
interferometer which allows a comparison of two many-body quantum states by
performing a measurement of the control atom.
\\ ( , 581kb)
Date: Fri, 7 Nov 2008 14:53:17 GMT (725kb)

Title: Spinor Dynamics of Quantum Accelerator Modes near Higher Order
Authors: L. Rebuzzini, I. Guarneri, and R. Artuso
Categories: quant-ph
Comments: 16 pages, 7 figures
   Quantum Accelerator Modes were discovered in experiments with Kicked Cold
Atoms in the presence of gravity. They were shown to be tightly related to
resonances of the Quantum Kicked Rotor. In this paper a spinor formalism is
developed for the analysis of Modes associatedwith resonances of arbitrary
order q>1. Decoupling of spin variables from orbital ones is achieved by means
of an ansatz of the Born-Oppenheimer type, that generates q independent band
dynamics. Each of these is described, in classical terms, by a map, and the
stable periodic orbits of this map give rise to quantum accelerator modes,
which are potentially observable in experiments. The arithmetic organization of
such periodic orbits is briefly discussed.
\\ ( , 725kb)
Date: Fri, 7 Nov 2008 15:48:30 GMT (143kb)

Title: Experimental study of vapor-cell magneto-optical traps for efficient
   trapping of radioactive atoms
Authors: S. N. Atutov, R. Calabrese, A. Facchini, G. Stancari, L. Tomassetti
Categories: physics.atom-ph physics.ins-det
Comments: 9 pages, 7 figures, submitted to Eur. Phys. J. D
   We have studied magneto-optical traps (MOTs) for efficient on-line trapping
of radioactive atoms. After discussing a model of the trapping process in a
vapor cell and its efficiency, we present the results of detailed experimental
studies on Rb MOTs. Three spherical cells of different sizes were used. These
cells can be easily replaced, while keeping the rest of the apparatus
unchanged: atomic sources, vacuum conditions, magnetic field gradients, sizes
and power of the laser beams, detection system. By direct comparison, we find
that the trapping efficiency only weakly depends on the MOT cell size. It is
also found that the trapping efficiency of the MOT with the smallest cell,
whose diameter is equal to the diameter of the trapping beams, is about 40%
smaller than the efficiency of larger cells. Furthermore, we also demonstrate
the importance of two factors: a long coated tube at the entrance of the MOT
cell, used instead of a diaphragm; and the passivation with an alkali vapor of
the coating on the cell walls, in order to minimize the losses of trappable
atoms. These results guided us in the construction of an efficient
large-diameter cell, which has been successfully employed for on-line trapping
of Fr isotopes at INFN's national laboratories in Legnaro, Italy.
\\ ( , 143kb)
Date: Fri, 7 Nov 2008 21:13:17 GMT (726kb)

Title: Superfluid and supersolid phases of lattice bosons with ring-exchange
Authors: Robert Schaffer, Anton A. Burkov and Roger G. Melko
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 7 pages, 5 figures
   We examine the superfluid phase of a hard-core boson model with
nearest-neighbor exchange J and four-particle ring-exchange K at half-filling
on the square lattice. At zero temperature we find that the superfluid in the
pure-J model is quickly destroyed by the inclusion of negative-K ring-exchange
interactions, favoring a state with a (pi,pi) ordering wavevector. Minimization
of the mean-field energy suggests that a supersolid state with coexisting
superfluidity, charge-density wave, and valence-bond-like order is formed. We
also study the behavior of the finite-T Kosterlitz-Thouless phase transition in
the superfluid phase, by forcing the Nelson-Kosterlitz universal jump condition
on the finite-T spin wave superfluid density. Away from the pure J point,
T_{KT} decreases rapidly for negative K, while for positive K, T_{KT} reaches a
maximum at some K \neq 0 in agreement with recent quantum Monte Carlo
\\ ( , 726kb)
Date: Fri, 7 Nov 2008 22:30:39 GMT (605kb)

Title: Stability and Excitations of a Dipolar Bose-Einstein Condensate with a
Authors: Ryan M. Wilson, Shai Ronen and John L. Bohn
Categories: cond-mat.other
Comments: 18 pages (preprint), 4 figures, submitted to PRA
   We study the stability of singly- and doubly-quantized vortex states of
harmonically trapped dipolar Bose-Einstein Condensates (BECs) by calculating
the low-lying excitations of these condensates. We map the dynamical stability
of these vortices as functions of the dipole-dipole interaction strength and
trap geometry by finding where their excitations have purely real energy
eigenvalues. In contrast to BECs with purely contact interactions, we find that
dipolar BECs in singly-quantized vortex states go unstable to modes with an
increasing number of angular and radial nodes for more oblate trap aspect
ratios, corresponding to \emph{local} collapse that occurs on a characteristic
length scale. Additionally, we find that dipolar BECs in doubly-quantized
vortex states are unstable to decay into a different topological state (with
two singly-quantized vortices) for all interaction strengths when the trap
geometry is sufficiently prolate to make the dipoles attractive, and in windows
of interaction strength when the trap geometry is sufficiently oblate to make
the dipoles repulsive.
\\ ( , 605kb)
Date: Sun, 9 Nov 2008 05:09:31 GMT (111kb)

Title: Signatures of the superfluid to Mott insulator transition in cold
   bosonic atoms in a one dimensional optical lattice
Authors: S. Ramanan, Tapan Mishra, Meetu Sethi Luthra, Ramesh V. Pai, B. P. Das
Categories: cond-mat.other cond-mat.stat-mech
Comments: 8 pages, 14 figures
   We study the Bose-Hubbard model using the finite size density matrix
renormalization group method. We obtain for the first time a complete phase
diagram for a system in the presence of a harmonic trap and compare it with
that of the homogeneous system. To realize the transition from the superfluid
to the Mott insulator phase we investigate different experimental signatures of
these phases in quantities such as momentum distribution, visibility,
condensate fraction and the total number of bosons at a particular density. The
relationships between the various experimental signatures and the phase diagram
are highlighted.
\\ ( , 111kb)
Date: Mon, 10 Nov 2008 18:33:57 GMT (1306kb)

Title: Multiband bosons in optical lattices
Authors: J. Larson, A. Collin, and J.-P. Martikainen
Categories: cond-mat.other
Report-no: NORDITA-2008-50
   We study a gas of repulsively interacting bosons in an optical lattice and
explore the physics beyond the lowest band Hubbard model. By including the
lowest band and first excited bands and utilizing a generalized Gutzwiller
ansatz we find how the lowest band physics is modified by the inclusion of the
first excited bands. In contrast to the prediction of the lowest band
Bose-Hubbard model we find a reentrant behavior of superfluidity and decreasing
width of the Mott lobes at strong coupling.
\\ ( , 1306kb)
Date: Mon, 10 Nov 2008 17:15:05 GMT (1654kb)

Title: Squeezed Light and Entangled Images from Four-Wave-Mixing in Hot
   Rubidium Vapor
Authors: Raphael C Pooser, Vincent Boyer, Alberto M. Marino, Paul D. Lett
Categories: quant-ph
Comments: 11 pages, 8 figures. SPIE Optics and Photonics 2008 proceeding (San
   Diego, CA)
   Entangled multi-spatial-mode fields have interesting applications in quantum
information, such as parallel quantum information protocols, quantum computing,
and quantum imaging. We study the use of a nondegenerate four-wave mixing
process in rubidium vapor at 795 nm to demonstrate generation of
quantum-entangled images. Owing to the lack of an optical resonator cavity, the
four-wave mixing scheme generates inherently multi-spatial-mode output fields.
We have verified the presence of entanglement between the multi-mode beams by
analyzing the amplitude difference and the phase sum noise using a dual
homodyne detection scheme, measuring more than 4 dB of squeezing in both cases.
This paper will discuss the quantum properties of amplifiers based on
four-wave-mixing, along with the multi mode properties of such devices.
\\ ( , 1654kb)
Date: Sat, 8 Nov 2008 15:45:17 GMT (701kb)

Title: Weakly interacting Bose gas in a random environment
Authors: G.M. Falco, T. Nattermann and V.L. Pokrovsky
Categories: quant-ph
   Zero temperature properties of a dilute weakly interacting $d$-dimensional
Bose gas in a random potential are studied. We calculate geometrical and
energetic characteristics of the localized state of a gas confined in a large
box or in a harmonic trap. Different regimes of the localized state are found
depending on the ratio of two characteristic length scales of the disorder, the
Larkin length and the disorder correlation length. Repulsing bosons confined in
a large box with average density $n$ well below a critical value $n_c$ are
trapped in deep potential wells of extension much smaller than distance between
them. Tunneling between these wells is exponentially small. The ground state of
such a gas is a random singlet with no long-range phase correlation For $n>n_c$
repulsion between particles overcomes the disorder and the gas transits from
the localized to a coherent superfluid state. The critical density $n_c$ is
calculated in terms of the disorder parameters and the interaction strength.
For atoms in traps four different regimes are found, only one of it is
superfluid. The theory is extended to lower (1 and 2) dimensions. Its
quantitative predictions can be checked in experiments with ultracold atomic
gases and other Bose-systems.
\\ ( , 701kb)
Date: Mon, 10 Nov 2008 06:26:00 GMT (875kb)

Title: Fermions on atom chips
Authors: Marcius H. T. Extavour, Lindsay J. LeBlanc, Jason McKeever, Alma B.
   Bardon, Seth Aubin, Stefan Myrskog, Thorsten Schumm and Joseph H. Thywissen
Categories: quant-ph
Comments: 33 pages, 10 figures
   We review our recent and ongoing work with Fermi gases on an atom chip. After
reviewing some statistical and thermodynamic properties of the ideal,
non-interacting Fermi gas, and a brief description of our atom chip and its
capabilities, we discuss our experimental approach to producing a potassium-40
degenerate Fermi gas (DFG) using sympathetic cooling by a rubidium-87
Bose-Einstein condensate on an atom chip. In doing so, we describe the factors
affecting the loading efficiency of the atom chip microtrap. This is followed
by a discussion of species selectivity in radio frequency manipulation of the
Bose-Fermi mixture, which we explore in the context of sympathetic evaporative
cooling and radio-frequency dressed adiabatic double-well potentials. Next, we
describe the incorporation of a crossed-beam dipole trap into the atom chip
setup, in which we generate and manipulate strongly interacting spin mixtures
of potassium-40. Finally, we conclude with a brief discussion of future
research directions with DFGs and atom chips. This article is to be included in
a forthcoming, broader volume on atom chips.
\\ ( , 875kb)
Date: Mon, 10 Nov 2008 19:19:17 GMT (437kb)

Title: Suppression or enhancement of the Fulde-Ferrell-Larkin-Ovchinnikov order
   in a one-dimensional optical lattice with particle correlated tunnelling
Authors: B. Wang and L.-M. Duan
Categories: quant-ph
   We study through controlled numerical simulation the ground state properties
of spin-polarized strongly interacting fermi gas in an anisotropic optical
lattice, which is described by an effective one-dimensional general Hubbard
model with particle correlated hopping rate. We show that the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type of state, while enhanced by a
negative correlated hopping rate, can be completely suppressed by positive
particle correlated hopping, yielding to an unusual magnetic phase even for
particles with on-site attractive interaction We also find several different
phase separation patterns for these atoms in an inhomogeneous harmonic trap,
depending on the correlated hopping rate.
\\ ( , 437kb)
Date: Tue, 11 Nov 2008 02:04:25 GMT (1651kb)

Title: Casimir interaction among heavy fermions in the BCS-BEC crossover
Authors: Yusuke Nishida
Categories: cond-mat.other
Comments: 10 pages, 6 figures
Report-no: MIT-CTP 3996
   We investigate a two-species Fermi gas with a large mass ratio interacting by
an interspecies short-range interaction. Using the Born-Oppenheimer
approximation, we determine the interaction energy of two heavy fermions
immersed in the Fermi sea of light fermions as a function of the s-wave
scattering length. In the BCS limit, we recover the perturbative calculation of
the effective interaction between heavy fermions. The p-wave projection of the
effective interaction is attractive in the BCS limit while it turns out to be
repulsive near the unitarity limit. We find that the p-wave attraction reaches
its maximum between the BCS and unitarity limits, where the maximal p-wave
pairing of heavy minority fermions is expected. We also investigate the case
where the heavy fermions are confined in two dimensions and the p-wave
attraction between them is found to be stronger than that in three dimensions.
\\ ( , 1651kb)
Date: Tue, 11 Nov 2008 09:44:12 GMT (26kb)

Title: Entropy entrainment and dissipation in superfluid Helium
Authors: N. Andersson and G.L. Comer
Categories: cond-mat.other
   We discuss finite temperature effects in superfluid Helium, providing a
direct demonstration that a model based on treating the excitations in the
system as a massless "entropy" fluid is equivalent to the traditional two-fluid
approach. In particular, we demonstrate how the entropy entrainment is related
to the "normal fluid density". We also show how the superfluid constraint of
irrotationality reduces the number of dissipation coefficients in the system.
This analysis provides insight into the more general problem when vortices are
present in the superfluid, and we discuss how the so-called mutual friction
force can be accounted for. The end product is a formalism for finite
temperature effects in a single condensate that can be applied to Helium in the
low temperature regime. It can also be used to describe (to a certain extent)
colour-flavour locked quark superconductors that may be present at the extreme
densities in a neutron star core.
\\ ( , 26kb)
Date: Tue, 11 Nov 2008 10:22:41 GMT (78kb)

Title: Free-fall expansion of finite-temperature Bose-Einstein condensed gas in
   the non Thomas-Fermi regime
Authors: M. Zawada, R. Abdoul, J. Chwede\'nczuk, R. Gartman, J. Szczepkowski,
   L. Tracewski, M. Witkowski, W. Gawlik
Categories: cond-mat.other
Comments: 8 pages, 4 figures
   We report on our study of the free-fall expansion of a finite-temperature
Bose-Einstein condensed cloud of 87Rb. The experiments are performed with a
variable total number of atoms while keeping constant the number of atoms in
the condensate. The results provide evidence that the BEC dynamics depends on
the interaction with thermal fraction. In particular, they provide experimental
evidence that thermal cloud compresses the condensate.
\\ ( , 78kb)
Date: Tue, 11 Nov 2008 17:16:59 GMT (32kb)

Title: Towards A Possible Charge-Kondo effect in Optical Lattices
Authors: M.S. Laad and A. Taraphder
Categories: cond-mat.str-el cond-mat.supr-con
Comments: submitted to Phys. Rev. Lett
   The Kondo effect underpins a large body of recent developments in the physics
of $d$- and $f$-band compounds. Although its {\it charge} analog is a rarity in
solids, the recent observations of the charge Kondo effect and the consequent
rise in superconducting T$_c$ encourage a search for other accessible systems.
Motivated by the possibility of wilfully tuning the {\it sign} of the
inter-electronic interaction in optical lattices, we study conditions for the
elusive {\it charge Kondo liquid} (CKL) state to manifest. We propose that a
combination of Feshbach resonances and sequentially controlled laser pulses may
produce the CKL. We show that the CKL is {\it never} a stable ground state,
appearing only when the ordered ground states are destabilized. Finally, we
discuss interesting analogies with nuclear matter.
\\ ( , 32kb)
arXiv:0811.1166 (*cross-listing*)
Date: Fri, 7 Nov 2008 16:04:45 GMT (24kb)

Title: The ground state energy of the weakly interacting Bose gas at high
Authors: Alessandro Giuliani, Robert Seiringer
Categories: math-ph cond-mat.stat-mech math.MP
Comments: RevTeX4, 16 pages
   We prove the Lee-Huang-Yang formula for the ground state energy of the 3D
Bose gas with repulsive interactions described by the exponential function, in
a simultaneous limit of weak coupling and high density. In particular, we show
that the Bogoliubov approximation is exact in an appropriate parameter regime,
as far as the ground state energy is concerned.
\\ ( , 24kb)
Date: Tue, 11 Nov 2008 00:04:53 GMT (70kb)

Title: Reactive Collisions of Ultracold Molecules Confined in quasi-2D Geometry
Authors: Z. Li and R. V. Krems
Categories: physics.atom-ph physics.chem-ph
Comments: 4pages
   We present a formalism for rigorous calculations of cross sections for
reactive collisions of ultracold atoms and molecules confined by laser fields
in quasi-2D geometry. We use the method to elucidate the general features of
inelastic scattering and chemical reactions in ultracold quasi-2D gases. Our
results indicate that the elastic-to-inelastic ratios of collision cross
sections are generally enhanced in the presence of a laser confinement and that
the threshold energy dependence of the collision cross sections can be tuned by
varying the confinement strength and external magnetic fields.
\\ ( , 70kb)
Date: Wed, 12 Nov 2008 11:48:48 GMT (1304kb)

Title: Density profiles of polarized Fermi gases confined in harmonic traps
Authors: G. Bertaina and S. Giorgini
Categories: cond-mat.other cond-mat.supr-con
Comments: 6 pages, 4 figures
   On the basis of the phase diagram of the uniform system we calculate the
density profiles of a trapped polarized Fermi gas at zero temperature using the
local density approximation. By varying the overall polarization and the
interaction strength we analyze the appearance of a discontinuity in the
profile, signalling a first order phase transition from a superfluid inner core
to a normal outer shell. The local population imbalance between the two
components and the size of the various regions of the cloud corresponding to
different phases are also discussed. The calculated profiles are quantitatively
compared with the ones recently measured by Shin {\it et al.}, Phys. Rev. Lett.
{\bf 101}, 070404 (2008).
\\ ( , 1304kb)
Date: Wed, 12 Nov 2008 13:18:53 GMT (804kb)

Title: Wave patterns generated by a supersonic moving body in a binary
   Bose-Einstein condensate
Authors: Yu. G. Gladush, A. M. Kamchatnov, Z. Shi, P. G. Kevrekidis, D. J.
   Frantzeskakis, B. A. Malomed
Categories: cond-mat.other
Comments: 13 pages, 6 figures
   Generation of wave structures by a two-dimensional object (laser beam) moving
in a two-dimensional two-component Bose-Einstein condensate with a velocity
greater than both sound velocities of the mixture is studied by means of
analytical methods and systematic simulations of the coupled Gross-Pitaevskii
equations. The wave pattern features three regions separated by two Mach cones.
Two branches of linear patterns similar to the so-called "ship waves" are
located outside the corresponding Mach cones, and oblique dark solitons are
found inside the wider cone. An analytical theory is developed for the linear
patterns. A particular dark-soliton solution is also obtained, its stability is
investigated, and two unstable modes of transverse perturbations are
identified. It is shown that, for a sufficiently large flow velocity, this
instability has a convective character in the reference frame attached to the
moving body, which makes the dark soliton effectively stable. The analytical
findings are corroborated by numerical simulations.
\\ ( , 804kb)
Date: Wed, 12 Nov 2008 15:44:34 GMT (152kb)

Title: Symmetry-Breaking and Symmetry-Restoring Dynamics of a Mixture of
   Bose-Einstein Condensates in a Double Well
Authors: Indubala I Satija and Philip Naudus (George Mason University, Fairfax,
   VA), Radha Balakrishnan (Institute of Mathematical Sciences, Chennai, India),
   Jeffrey Heward, Mark Edwards (Department of Physics, Georgia Southern
   University, Statesboro, GA) and and Charles W Clark (National Institute of
   Standards and Technology, Gaithersburg, Maryland)
Categories: quant-ph
   We study the coherent nonlinear tunneling dynamics of a binary mixture of
Bose-Einstein condensates in a double-well potential. We demonstrate the
existence of a new type of mode associated with the "swapping" of the two
species in the two wells of the potential. In contrast to the symmetry breaking
macroscopic quantum self-trapping (MQST) solutions, the swapping modes
correspond to the tunneling dynamics that preserves the symmetry of the double
well potential. As a consequence of two distinct types of broken symmetry MQST
phases where the two species localize in the different potential welils or
coexist in the same well, the corresponding symmetry restoring swapping modes
result in dynamics where the the two species either avoid or chase each other.
In view of the possibility to control the interaction between the species, the
binary mixture offers a very robust system to observe these novel effects as
well as the phenomena of Josephson oscillations and pi-modes
\\ ( , 152kb)
Date: Wed, 12 Nov 2008 16:44:01 GMT (383kb)

Title: Matter-Wave Solitons in the Presence of Collisional Inhomogeneities:
   Perturbation theory and the impact of derivative terms
Authors: S. Middelkamp, P.G. Kevrekidis, D.J. Frantzeskakis, P. Schmelcher
Categories: quant-ph
Comments: 12 pages, 5 fugures
   We study the dynamics of bright and dark matter-wave solitons in the presence
of a spatially varying nonlinearity. When the spatial variation does not
involve zero crossings, a transformation is used to bring the problem to a
standard nonlinear Schrodinger form, but with two additional terms: an
effective potential one and a non-potential term. We illustrate how to apply
perturbation theory of dark and bright solitons to the transformed equations.
We develop the general case, but primarily focus on the non-standard special
case whereby the potential term vanishes, for an inverse square spatial
dependence of the nonlinearity. In both cases of repulsive and attractive
interactions, appropriate versions of the soliton perturbation theory are shown
to accurately describe the soliton dynamics.
\\ ( , 383kb)
Date: Wed, 12 Nov 2008 05:29:52 GMT (155kb)

Title: Measuring the frequency of a Sr optical lattice clock using a 120-km
   coherent optical transfer
Authors: F.-L. Hong, M. Musha, M. Takamoto, H. Inaba, S. Yanagimachi, A.
   Takamizawa, K. Watabe, T. Ikegami, M. Imae, Y. Fujii, M. Amemiya, K.
   Nakagawa, K. Ueda, and H. Katori
Categories: physics.atom-ph physics.optics
Comments: 14 pages, 3 figures
   We demonstrate a precision frequency measurement using a phase-stabilized
120-km optical fiber link over a physical distance of 50 km. The transition
frequency of the 87Sr optical lattice clock at the University of Tokyo is
measured to be 429228004229874.1(2.4) Hz referenced to international atomic
time (TAI). The measured frequency agrees with results obtained in Boulder and
Paris at a 6*10^-16 fractional level, which matches the current best
evaluations of Cs primary frequency standards. The results demonstrate the
excellent functions of the intercity optical fibre link, and the great
potential of optical lattice clocks for use in the redefinition of the second.
\\ ( , 155kb)
Date: Thu, 13 Nov 2008 09:32:21 GMT (19kb)

Title: Cooling into the Spin-Nematic State for a Spin-1 Bose gase in an optical
Authors: Ming-Chiang Chung and Sungkit Yip
Categories: cond-mat.other
Comments: 2 figures
   The possibility of adiabatically cooling a spin-1 polar Bose gas to a
spin-nematic phase is theoretically discussed. The relation between the order
parameter of the final spin-nematic phase and the starting temperature of the
spinor Bose gas is obtained both using the mean-field approach for the high
temperature and spin-wave approach for the low temperature. We find that there
exists a good possibility to reach the spin-nematic ordering starting with
spinor antiferromagnetic Bose gases.
\\ ( , 19kb)
Date: Thu, 13 Nov 2008 10:56:11 GMT (619kb)

Title: The canonical heat capacity of normal mesoscopic fermion systems: the
   temperature evolution and particle number oscillations
Authors: N. K. Kuzmenko and V. M.Mikhajlov
Categories: cond-mat.stat-mech cond-mat.mes-hall
Comments: 44 pages, 25 figures, to appear in Statistical Mechanics (Nova
   Science Publishers, N.Y., USA) 2008
   The heat capacity (C) of a mesoscopic nonsuperconducting fermion system
treated as a canonical ensemble of independent particles is studied in a wide
range of particle numbers and temperatures which vary from values close to zero
up to the Fermi energy. The temperature evolution of C is naturally divided
into four stages. On the first one the heat capacity exponentially increases
with temperature and at a resonance temperature reaches either a local maximum
or an irregularity in its growth. This resonance temperature being measured can
give information concerning the level spacings in the immediate proximity of
the Fermi energy. On the second stage the progressive suppression of the level
density oscillations takes place. During this stage oscillations of C v.s.
particle number N can be distinctly observed. These oscillations give the
N-variations of the temperature averaged level density. The growth of C on the
third stage of the evolution is governed by the T-linear law if the particle
number is large enough (N>1000). It is found that the Sommerfeld factor in the
linear law for such small systems shows more complicated N-dependence as
compared with large systems where C is strictly proportional to N. For
temperatures tending to the Fermi energy the deviations from the T-linearity
are evident and at T larger than the Fermi energy (the fourth stage of the
evolution) any system attains to the classic Boltzmann-Maxwell limit
irrespective of the particle
\\ ( , 619kb)
Date: Thu, 13 Nov 2008 04:51:43 GMT (547kb)

Title: A comparative study of dynamical simulation methods for the dissociation
   of molecular Bose-Einstein condensates
Authors: S. L. W. Midgley, S. Wuester, M. K. Olsen, M. J. Davis and K. V.
Categories: quant-ph
Comments: 11 pages, 7 figures
   We describe a pairing mean-field theory related to the
Hartree-Fock-Bogoliubov approach, and apply it to the dynamics of dissociation
of a molecular Bose-Einstein condensate (BEC) into correlated bosonic atom
pairs. We also perform the same simulation using two stochastic phase-space
techniques for quantum dynamics -- the positive P-representation method and the
truncated Wigner method. By comparing the results of our calculations we are
able to assess the relative strength of these theoretical techniques in
describing molecular dissociation in one spatial dimension. An important aspect
of our analysis is the inclusion of atom-atom interactions which can be
problematic for the positive-P method. We find that the truncated Wigner method
mostly agrees with the positive-P simulations, but can be simulated for
significantly longer times. The pairing mean-field theory results diverge from
the quantum dynamical methods after relatively short times.
\\ ( , 547kb)
Date: Thu, 13 Nov 2008 15:44:33 GMT (1292kb,D)

Title: Coherent state approach to the cross collisional effects in the
   population dynamics of a two-mode Bose-Einstein condensate
Authors: Thiago F. Viscondi, K. Furuya and M. C. de Oliveira
Categories: quant-ph
Comments: 19 pages, 8 figures
   We reanalyze the non-linear population dynamics of a Bose-Einstein Condensate
(BEC) in a double well trap considering a semiclassical approach based on a
time dependent variational principle applied to coherent states associated to
SU(2) group. Employing a two-mode local approximation and hard sphere type
interaction, we show in the Schwinger's pseudo-spin language the occurrence of
a fixed point bifurcation that originates a separatrix of motion on a sphere.
This separatrix corresponds to the borderline between two dynamical regimes of
Josephson oscillations and mesoscopic self-trapping. We also consider the
effects of interaction between particles in different wells, known as cross
collisions. Such terms are usually neglected for traps sufficiently far apart,
but recently it has been shown that they contribute to the effective tunneling
constant with a factor growing linearly with the particle number. This effect
changes considerably the effective tunneling of the system for sufficiently
large number of trapped atoms, in perfect accord with experimental data.
Finally, we identify analytically the transition parameter associated to the
bifurcation in the generalized phase space of the model with cross-collision
terms, and show how the dynamical regime depends on the initial conditions of
the system and the collisional parameters values.
\\ ( , 1292kb)
Date: Thu, 13 Nov 2008 17:42:00 GMT (293kb)

Title: Laser frequency stabilization to highly excited state transitions using
   electromagnetically induced transparency in a cascade system
Authors: R. P. Abel, A. K. Mohapatra, M. G. Bason, J. D. Pritchard, K. J.
   Weatherill, U. Raitzsch and C. S. Adams
Categories: quant-ph
Comments: 3 pages, 4 figures
   We demonstrate laser frequency stabilization to excited state transitions
using cascade electromagnetically induced transparency (EIT). Using a room
temperature Rb vapor cell as a reference, we stabilize a first diode laser to
the D2 transition and a second laser to a transition from the intermediate
state to a Rydberg state with principal quantum number n=19 - 70. A combined
laser linewidth of 280 kHz over a 0.1 ms time period is achieved. This method
may be applied generally to any cascade system and allows laser stabilization
to an atomic reference in the absence of strong optical transitions.
\\ ( , 293kb)

The replacements:

replaced with revised version Thu, 6 Nov 2008 22:57:27 GMT (10kb)

Title: The Rayleigh-Taylor Instability in a Bose-Einstein Condensate
Authors: Swarbhanu Chatterjee
Categories: cond-mat.mes-hall cond-mat.mtrl-sci
Comments: 5 pages. One reference in the introduction of the previous version
   has been deleted as not being relevant to the paper. The physical formulation
   is unchanged except for one point of difference - the initial state in which
   the condensate is prepared is different. The presentation of the paper has
   been changed
\\ ( , 10kb)
replaced with revised version Fri, 7 Nov 2008 02:10:17 GMT (1037kb)

Title: Mott Phase in Polarized Two-component Atomic Fermi Lattice Gas:A
   Playground for S=1/2 Heisenberg Model in Magnetic Field
Authors: M. Machida, M. Okumura, S. Yamada, T. Deguchi, Y. Ohashi, H. Matsumoto
Categories: cond-mat.str-el
\\ ( , 1037kb)
replaced with revised version Fri, 7 Nov 2008 02:09:20 GMT (217kb)

Title: Phase Separation in two-Species Atomic Bose-Einstein Condensate with
   Interspecies Feshbach Resonance
Authors: Lu Zhou, Jing Qian, Han Pu, Weiping Zhang, and Hong Y. Ling
Categories: cond-mat.mes-hall cond-mat.other
Comments: 9 pages, 3 figures
Journal-ref: Phys. Rev. A 78, 053612 (2008)
DOI: 10.1103/PhysRevA.78.053612
\\ ( , 217kb)
replaced with revised version Fri, 7 Nov 2008 16:21:19 GMT (101kb)

Title: Casimir Energy of a BEC: From Moderate Interactions to the Ideal Gas
Authors: J\"urgen Schiefele, Carsten Henkel
Categories: cond-mat.other
Comments: 12 pages, 3 figures, accepted for publication in JPA. New version
   with corrected typos and an additional appendix
\\ ( , 101kb)
replaced with revised version Mon, 10 Nov 2008 20:58:06 GMT (363kb)

Title: Possibility of supersolid with repulsive fermions in an anisotropic
   optical lattice near a Feshbach resonance
Authors: B. Wang and L.-M. Duan
Categories: cond-mat.other cond-mat.str-el
Comments: updated with published version
Journal-ref: New Journal of Physics 10, 073007 (2008)
\\ ( , 363kb)
replaced with revised version Sun, 9 Nov 2008 01:01:18 GMT (53kb)

Title: Threshold for Chaos and Thermalization in One-Dimensional Mean-Field
   Bose-Hubbard Model
Authors: Amy C. Cassidy, Douglas Mason, Vanja Dunjko, Maxim Olshanii
Categories: cond-mat.other cond-mat.stat-mech
Comments: 4 pages, 3 figures
\\ ( , 53kb)
replaced with revised version Fri, 7 Nov 2008 22:29:41 GMT (24kb)

Title: Microscopic diagonal entropy and its connection to basic thermodynamic
Authors: Roman Barankov and Anatoli Polkovnikov
Categories: cond-mat.stat-mech hep-th quant-ph
Comments: minor changes, added references
\\ ( , 24kb)
replaced with revised version Tue, 11 Nov 2008 19:23:40 GMT (8kb)

Title: Hydrodynamics of Bose and Fermi superfluids at zero temperature: the
   superfluid nonlinear Schrodinger equation
Authors: Luca Salasnich (CNR-INFM and CNISM, University of Padua)
Categories: cond-mat.stat-mech cond-mat.other
Comments: 4 pages, no figures, prepared for the Special Issue of Laser Physics:
   Physics of Cold Trapped Atoms; in the second version corrected some typos; in
   the third version added some useful comments. To be published in Laser
   Physics (April 2009)
\\ ( , 8kb)
arXiv:0807.5072 (*cross-listing*)
replaced with revised version Tue, 11 Nov 2008 16:00:44 GMT (40kb)

Title: Not to normal order - Notes on the kinetic limit for weakly interacting
   quantum fluids
Authors: Jani Lukkarinen, Herbert Spohn
Categories: math-ph math.MP quant-ph
Comments: 43 pages, corrected typos, updated assumptions in sec. 7
MSC-class: 82C10; 82C40
\\ ( , 40kb)
replaced with revised version Wed, 12 Nov 2008 17:24:46 GMT (36kb)

Title: Quasiparticle excitations and dynamic susceptibilities in the BCS-BEC
Authors: J. Bauer and A.C. Hewson
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 6 pages, 5 figures (minor amendment and additional reference)
\\ ( , 36kb)
replaced with revised version Thu, 13 Nov 2008 19:15:39 GMT (184kb,D)

Title: Stabilization of Solitons Generated by a Supersonic Flow of
   Bose-Einstein Condensate Past an Obstacle
Authors: A.M. Kamchatnov, L.P. Pitaevskii
Categories: cond-mat.other nlin.PS
Comments: 5 pages, 3 figures, final version published in Phys. Rev. Lett
Journal-ref: Phys. Rev. Lett. 100, 160402 (2008)
\\ ( , 184kb)

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
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 Nov 17 2008 - 13:01:20 EST

This archive was generated by hypermail 2.2.0 : Tue Jan 06 2009 - 10:41:32 EST