[Matts-arxiv] Matt's arXiv selection: week ending 2 July 2010

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Tue, 24 Aug 2010 22:53:55 +1000

Dear subscribers,

This week's selection was compiled by Mike Garrett, and contains 35 new
abstracts and 12 replacements.

arXiv:0910.1749 (*cross-listing*)
Date: Fri, 9 Oct 2009 14:41:16 GMT (186kb)
Date (revised v2): Tue, 1 Dec 2009 14:25:44 GMT (186kb)
Date (revised v3): Fri, 14 May 2010 13:48:33 GMT (187kb)

Title: Fermionization dynamics of a strongly interacting 1D Bose gas after an
   interaction quench
Authors: Dominik Muth, Bernd Schmidt, and Michael Fleischhauer
Categories: quant-ph cond-mat.quant-gas physics.comp-ph
Comments: 10 pages, 4 figures
   We study the dynamics of a one-dimensional Bose gas after a sudden change of
the interaction strength from zero to a finite value using the numerical
time-evolving block decimation (TEBD) algorithm. It is shown that despite the
integrability of the system, local quantities such as the two-particle
correlation g^(2)(x, x) attain steady state values in a short characteristic
time inversely proportional to the Tonks parameter gamma and the square of the
density. The asymptotic values are very close to those of a finite temperature
grand canonical ensemble with a local temperature corresponding to initial
energy and density. Non-local density-density correlations on the other hand
approach a steady state on a much larger time scale determined by the finite
propagation velocity of oscillatory correlation waves.
\\ ( http://arxiv.org/abs/0910.1749 , 187kb)
arXiv:1004.2408 (*cross-listing*)
Date: Wed, 14 Apr 2010 14:34:38 GMT (149kb)
Date (revised v2): Fri, 16 Apr 2010 00:45:25 GMT (177kb)
Date (revised v3): Wed, 30 Jun 2010 15:05:36 GMT (178kb)

Title: Preparation of stable excited states in an optical lattice via sudden
   quantum quench
Authors: Li Wang, Yajiang Hao, and Shu Chen
Categories: cond-mat.quant-gas quant-ph
Comments: 5 pages, 4 figures
Journal-ref: Phys. Rev. A 81, 063637 (2010)
DOI: 10.1103/PhysRevA.81.063637
   We study how stable excited many-body states of the Bose-Hubbard model,
including both the gas-like state for strongly attractive bosons and bound
cluster state for repulsive bosons, can be produced with cold bosonic atoms in
an one-dimensional optical lattice. Starting from the initial ground states of
strongly interacting bosonic systems, we can achieve stable excited states of
the systems with opposite interaction strength by suddenly switching the
interaction to the opposite limit. By exactly solving dynamics of the
Bose-Hubbard model, we demonstrate that the produced excited state can be a
very stable dynamic state. This allows the experimental study of excited state
properties of ultracold atoms system in optical lattices.
\\ ( http://arxiv.org/abs/1004.2408 , 178kb)
arXiv:1004.4099 (*cross-listing*)
Date: Fri, 23 Apr 2010 11:19:48 GMT (198kb)

Title: Discretized vs. continuous models of p-wave interacting fermions in 1D
Authors: Dominik Muth, Michael Fleischhauer, and Bernd Schmidt
Categories: quant-ph cond-mat.quant-gas physics.comp-ph
Comments: 7 pages, 5 figures
   We present a general mapping between continuous and lattice models of Bose-
and Fermi-gases in one dimension, interacting via local two-body interactions.
For s-wave interacting bosons we arrive at the Bose-Hubbard model in the weakly
interacting, low density regime. The dual problem of p-wave interacting
fermions is mapped to the spin-1/2 XXZ model close to the critical point in the
highly polarized regime. The mappings are shown to be optimal in the sense that
they produce the least error possible for a given discretization length. As an
application we examine the ground state of a interacting Fermi gas in a
harmonic trap, calculating numerically real-space and momentum-space
distributions as well as two-particle correlations. In the analytically known
limits the convergence of the results of the lattice model to the continuous
one is shown.
\\ ( http://arxiv.org/abs/1004.4099 , 198kb)
arXiv:1005.1584 (*cross-listing*)
Date: Mon, 10 May 2010 15:22:32 GMT (15kb)
Date (revised v2): Fri, 25 Jun 2010 10:35:56 GMT (16kb)

Title: Diamagnetism of quantum gases with singular potentials
Authors: Philippe Briet (CPT), Horia D. Cornean (MATH. DEPT., AALBORG
   UNIVERSITY), Baptiste Savoie (CPT)
Categories: math-ph cond-mat.quant-gas cond-mat.stat-mech math.MP
   We consider a gas of quasi-free quantum particles confined to a finite box,
subjected to singular magnetic and electric fields. We prove in great
generality that the finite volume grand-canonical pressure is jointly analytic
in the chemical potential ant the intensity of the external magnetic field. We
also discuss the thermodynamic limit.
\\ ( http://arxiv.org/abs/1005.1584 , 16kb)
arXiv:1006.4755 (*cross-listing*)
Date: Thu, 24 Jun 2010 11:29:37 GMT (750kb)

Title: Hydrodynamic nucleation of vortices and solitons in a resonantly excited
   polariton superfluid
Authors: Simon Pigeon (MPQ), Iacopo Carusotto (CRS BEC-INFM), Cristiano Ciuti
Categories: cond-mat.other physics.optics
   We present a theoretical study of the hydrodynamic properties of a quantum
gas of exciton-polaritons in a semiconductor microcavity under a resonant laser
excitation. The effect of a spatially extended defect on the superfluid flow is
investigated as a function of the flow speed. The processes that are
responsible for the nucleation of vortices and solitons in the wake of the
defect are characterized, as well as the regimes where the superfluid flow
remains unperturbed. Specific features due to the non-equilibrium nature of the
polariton fluid are put in evidence.
\\ ( http://arxiv.org/abs/1006.4755 , 750kb)
arXiv:1006.4798 (*cross-listing*)
Date: Thu, 24 Jun 2010 14:18:09 GMT (2440kb,D)

Title: Variational calculations on multilayer stacks of dipolar Bose-Einstein
Authors: Andrej Junginger, J\"org Main, G\"unter Wunner
Categories: cond-mat.quant-gas nlin.CD quant-ph
Comments: 9 pages, 9 figures
   We investigate a multilayer stack of dipolar Bose-Einstein condensates in
terms of a simple Gaussian variational ansatz and demonstrate that this
arrangement is characterized by the existence several stationary states. Using
a Hamiltonian picture we show that in an excited stack there is a coupled
motion of the individual condensates by which they exchange energy. We find
that for high excitations the interaction between the single condensates can
induce the collapse of one of them. We furthermore demonstrate that one
collapse in the stack can force other collapses, too. We discuss the
possibility of experimentally observing the coupled motion and the relevance of
the variational results found to full numerical investigations.
\\ ( http://arxiv.org/abs/1006.4798 , 2440kb)
arXiv:1006.4950 (*cross-listing*)
Date: Fri, 25 Jun 2010 09:58:07 GMT (79kb,D)

Title: Mean-field regime of trapped dipolar Bose-Einstein condensates in one
   and two dimensions
Authors: Yongyong Cai, Matthias Rosenkranz, Zhen Lei and Weizhu Bao
Categories: cond-mat.quant-gas quant-ph
Comments: 9 pages, 5 figures
   We derive rigorous one- and two-dimensional mean-field equations for cigar-
and pancake-shaped dipolar Bose-Einstein condensates. We show how the dipolar
interaction modifies the contact interaction of the strongly confined atoms
with arbitrary polarization. In addition, our equations introduce a nonlocal
potential, which is anisotropic for pancake-shaped condensates. We propose to
observe this anisotropy via measurement of the condensate aspect ratio. We also
derive analytically approximate density profiles from our equations. Both the
numerical solutions of our reduced mean-field equations and the analytical
density profiles agree well with numerical solutions of the full
Gross-Pitaevskii equation while being more efficient to compute.
\\ ( http://arxiv.org/abs/1006.4950 , 79kb)
Date: Fri, 25 Jun 2010 11:30:49 GMT (210kb)

Title: Polarized superfluid state in a three-dimensional fermionic optical
Authors: A. Koga, J. Bauer, P.Werner, and Th. Pruschke
Categories: cond-mat.quant-gas
Comments: 6 pages, 2 figures
   We study ultracold fermionic atoms trapped in a three dimensional optical
lattice by combining the real-space dynamical mean-field approach with
continuous-time quantum Monte Carlo simulations. For a spin-unpolarized system
we show results the density and pair potential profile in the trap for a range
of temperatures. We discuss how a polarized superfluid state is spatially
realized in the spin-polarized system with harmonic confinement at low
temperatures and present the local particle density, local magnetization, and
pair potential.
\\ ( http://arxiv.org/abs/1006.4965 , 210kb)
Date: Fri, 25 Jun 2010 14:03:39 GMT (78kb)

Title: Are unequal-mass Fermi gases with infinite scattering length universal?
Authors: D. Blume and K. M. Daily
Categories: cond-mat.quant-gas
Comments: 4 pages, 2 figures
   We treat small trapped unequal-mass two-component Fermi gases at unitarity
within a non-perturbative microscopic framework and investigate the system
properties as functions of the mass ratio $\kappa$, and the numbers $N_{1}$ and
$N_2$ of heavy and light fermions. While equal-mass Fermi gases with infinitely
large interspecies $s$-wave scattering length $a_s$ are universal, we find that
unequal mass Fermi gases are, for sufficiently large $\kappa$ and in the regime
where Efimov physics is absent, not universal. In particular, the
$(N_1,N_2)=(2,1)$ and $(3,1)$ systems exhibit three-body (3b) and four-body
(4b) resonances at $\kappa = 12.314(2)$ and $10.4(2)$, respectively, as well as
surprisingly large finite-range (FR) effects.
\\ ( http://arxiv.org/abs/1006.5002 , 78kb)
Date: Sat, 26 Jun 2010 14:49:38 GMT (1176kb,D)

Title: Spin-Orbit Coupled Spinor Bose-Einstein Condensates
Authors: Chunji Wang, Chao Gao, Chao-Ming Jian and Hui Zhai
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 4 pages, 4 figures
   An effective spin-orbit coupling can be generated in cold atom system by
engineering atom-light interactions. In this letter we study spin-$1/2$ and
spin-$1$ Bose-Einstein condensates with spin-orbit coupling. We find that a
uniform condensate is always unstable and the condensate wave function will
develop non-trivial structures. From numerical simulation we have identified
two different phases. In one phase there is a regular array of vortices
aligning through the center of condensate. In this phase, time-reversal
symmetry is broken and the ground state is two-fold degenerate. In the other
phase the condensate wave function forms a standing wave. The transition
between them is driven by interactions between bosons. We also provide an
analytical understanding of this result and determines the transition point
between these two phases.
\\ ( http://arxiv.org/abs/1006.5148 , 1176kb)
arXiv:1006.5167 (*cross-listing*)
Date: Sat, 26 Jun 2010 21:27:55 GMT (192kb)

Title: Demonstration of double EIT using coupled harmonic oscillators and RLC
Authors: Joshua Harden, Amitabh Joshi, and Juan D. Serna
Categories: quant-ph physics.class-ph physics.ed-ph
Comments: REVTeX, 9 pages, 10 figures
   Single and double electromagnetically induced transparency in a medium (EIT),
consisting of four-level atoms in the inverted-Y configuration, are discussed
by using mechanical and electrical analogies. A spring-mass system subject to
damping and driven by an external force is used to represent mechanically the
four-level atom. The equations of motion of this system are solved
analytically, and the revealed single and double EIT studied numerically. On
the other hand, three coupled RLC circuits are used, as the electrical analog,
to explore and demonstrate experimentally single and double EIT. The simplicity
of these two models makes this experiment appropriate for undergraduate
students and easy to incorporate into a college physics laboratory.
\\ ( http://arxiv.org/abs/1006.5167 , 192kb)
Date: Sun, 27 Jun 2010 02:22:14 GMT (35kb)

Title: Competition between paramagnetism and diamagnetism in charged Fermi
Authors: Xiaoling Jian, Jihong Qin, Qiang Gu
Categories: cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el
Comments: 4 pages, 3 figures
   The charged Fermi gas with a small Lande-factor $g$ is expected to be
diamagnetic, while that with a larger $g$ could be paramagnetic. We calculate
the critical value of the $g$-factor which separates the dia- and para-magnetic
regions. In the weak-field limit, $g_{c}$ has the same value both at high and
low temperatures, $g_{c}=1/\sqrt{12}$. Nevertheless, $g_{c}$ increases with the
temperature reducing in finite magnetic fields. We also compare the $g_{c}$
value of Fermi gases with those of Boltzmann and Bose gases, supposing the
particle has three Zeeman levels $\sigma=\pm1, 0$, and find that $g_{c}$ of
Bose and Fermi gases is larger and smaller than that of Boltzmann gases,
\\ ( http://arxiv.org/abs/1006.5179 , 35kb)
Date: Sun, 27 Jun 2010 08:21:14 GMT (14kb)

Title: Heavy-Light Few Fermion Clusters at Unitarity
Authors: S. Gandolfi and J. Carlson
Categories: cond-mat.quant-gas nucl-th
Comments: 4 pages, 2 figures
Report-no: LA-UR 10-04320
   We examine the physics of two, three, and four heavy fermions interacting
with a single light fermion via short-range interactions. Four-particle bosonic
Efimov states have proven important experimentally and also been the subject of
significant theoretical effort. Similar fermionic systems are just now being
investigated. We find that with some simple interactions the four- and
five-particle states collapse to the interaction range at smaller mass ratios
than the three-body state, and also before larger clusters can collapse. These
states and their excitations can be studied in cold atom experiments, providing
unique insights into the role of few-body systems in many-body physics.
\\ ( http://arxiv.org/abs/1006.5186 , 14kb)
Date: Sun, 27 Jun 2010 18:02:00 GMT (117kb)

Title: Glide and Superclimb of Dislocations in Solid $^4$He
Authors: D. Aleinikava, E. Dedits, A.B. Kuklov
Categories: cond-mat.other
Comments: Updated version submitted to JLTP as QFS2010 proceedings; 11 pages, 6
   Glide and climb of quantum dislocations under finite external stress,
variation of chemical potential and bias (geometrical slanting) in Peierls
potential are studied by Monte Carlo simulations of the effective string model.
We treat on unified ground quantum effects at finite temperatures $T$. Climb at
low $T$ is assisted by superflow along dislocation core -- {\it superclimb}.
Above some critical stress avalanche-type creation of kinks is found. It is
characterized by hysteretic behavior at low $T$. At finite biases gliding
dislocation remains rough even at lowest $T$ -- the behavior opposite to
non-slanted dislocations. In contrast to glide, superclimb is characterized by
quantum smooth state at low temperatures even for finite bias. In some
intermediate $T$-range giant values of the compressibility as well as
non-Luttinger type behavior of the core superfluid are observed.
\\ ( http://arxiv.org/abs/1006.5228 , 117kb)
arXiv:1006.5270 (*cross-listing*)
Date: Mon, 28 Jun 2010 06:25:27 GMT (42kb)

Title: Cyclotron dynamics of cold atoms in 2D optical lattices
Authors: Andrey R. Kolovsky
Categories: cond-mat.quant-gas quant-ph
Comments: EPL-style, 8 pages, 4 figures
   We propose a simple setup for introducing an artificial magnetic field for
neutral atoms in 2D optical lattices. This setup is based on the phenomenon of
photon-assistent tunneling and involves a low-frequency periodic driving of the
optical lattice. We also address the problem of detecting this effective
magnetic field. In particular, we discuss interference patterns of the atomic
wave function and study the center of mass wave-packet dynamics, which shows
some features of cyclotron dynamics of a classical charged particle.
\\ ( http://arxiv.org/abs/1006.5270 , 42kb)
Date: Mon, 28 Jun 2010 08:47:59 GMT (195kb)

Title: Features of interaction of microwaves with HeII
Authors: Valery Khodusov and A.S. Naumovets
Categories: cond-mat.other
Comments: 8 pages
   Based on interrelation between the thermodynamic and electromechanical
phenomena in superfluid helium, the explanation of experimentally found
features of microwave interaction in the frequency range of 40-200 GHz is
given. Due to fast roton-roton and roton-phonon interactions resonant
excitation on frequency correspond to minimal roton energy relaxes and forms a
wide pedestal. Alongside these fast processes, there are also slower processes
of rotons' scattering by microwave photons taking place, which lead to
additional absorption of energy of resonant microwaves and to the appearance of
a narrow resonant peak on the background of a wide pedestal. The theoretical
explanation of the influence which streams exert on resonant absorption of
microwaves is given. The critical velocity of stream at which absorption of
microwaves was replaced by their radiation is found.
\\ ( http://arxiv.org/abs/1006.5290 , 195kb)
arXiv:1006.5312 (*cross-listing*)
Date: Mon, 28 Jun 2010 10:42:53 GMT (34kb)

Title: Dynamics of pair correlations in the attractive Lieb-Liniger gas
Authors: Dominik Muth and Michael Fleischhauer
Categories: quant-ph cond-mat.quant-gas physics.comp-ph
Comments: 4 pages, 4 figures
   We investigate the dynamics of a 1D Bose gas after a quench from the
Tonks-Girardeau regime to the regime of strong attractive interactions applying
analytical techniques and exact numerical simulations. After the quench the
system is found to be predominantly in an excited gas-like state, the so-called
super-Tonks gas, however with a small coherent admixture of two-particle bound
states. Despite its small amplitude, the latter component leads to a rather
pronounced oscillation of the local density-density correlation with a
frequency corresponding to the binding energy of the pair, making two-particle
bound states observable in an experiment. Contributions from bound states with
larger particle numbers are found to be negligible.
\\ ( http://arxiv.org/abs/1006.5312 , 34kb)
arXiv:1006.5314 (*cross-listing*)
Date: Mon, 28 Jun 2010 11:03:36 GMT (65kb)

Title: Photoassociation of a cold atom-molecule pair: long-range
   quadrupole-quadrupole interactions
Authors: M. Lepers, O. Dulieu, and V. Kokoouline
Categories: quant-ph physics.atom-ph physics.chem-ph
Comments: 5 figures
   The general formalism of the multipolar expansion of electrostatic
interactions is applied to the calculation the potential energy between an
excited atom and a ground state diatomic molecule at large separations. Both
partners exhibit a permanent quadrupole moment, so that their mutual
quadrupole-quadrupole long-range interaction is attractive enough to bind
trimers. Numerical results are given for an excited Cs(6P) atom and a ground
state Cs2 molecule. The prospects for achieving photoassociation of a cold
atom/dimer pair is thus discussed and found promising. The formalism can be
easily generalized to the long-range interaction between molecules to
investigate the formation of cold tetramers.
\\ ( http://arxiv.org/abs/1006.5314 , 65kb)
Date: Mon, 28 Jun 2010 11:19:48 GMT (155kb)

Title: Equestion of Two-Fluid Hydrodynamics of Superfluid Helium with the
   Account of Electric Fields
Authors: V.D. Khodusov, A.S. Naumovets
Categories: cond-mat.other
Comments: 5 pages
   System of two-fluid hydrodynamics of superfluid helium with the account of
electric field is obtained. These equations are obtained in kinetic approach
using quasi-equilibrium distribution function of quasi-particles, which vanishs
collision integral of quasi-particles, and contains dependence on electric
field by means of phenomenological parameter {\alpha}. Using experimental data
at temperature range of 1,4 - 2 K, where basic role plays roton hydrodynamics,
the value of phenomenological parameter, is obtained.
\\ ( http://arxiv.org/abs/1006.5319 , 155kb)
Date: Tue, 29 Jun 2010 07:37:44 GMT (2133kb)

Title: Nonlinear Scattering of a Bose-Einstein Condensate on a Rectangular
Authors: Lincoln D. Carr, Rachel R. Miller, and Daniel R. Bolton
Categories: cond-mat.quant-gas nlin.PS
Comments: 14 pages, 15 figures
   We consider the nonlinear scattering and transmission of an atom laser, or
Bose-Einstein condensate (BEC) on a finite rectangular potential barrier. The
nonlinearity inherent in this problem leads to several new physical features
beyond the well-known picture from single-particle quantum mechanics. We find
numerical evidence for a denumerably infinite string of bifurcations in the
transmission resonances as a function of nonlinearity and chemical potential,
when the potential barrier is wide compared to the wavelength of oscillations
in the condensate. Near the bifurcations, we observe extended regions of
near-perfect resonance, in which the barrier is effectively invisible to the
BEC. Unlike in the linear case, it is mainly the barrier width, not the height,
that controls the transmission behavior. We show that the potential barrier can
be used to create and localize a dark soliton or dark soliton train from a
phonon-like standing wave.
\\ ( http://arxiv.org/abs/1006.5519 , 2133kb)
Date: Tue, 29 Jun 2010 08:35:40 GMT (215kb)

Title: Dynamic Structure Factor of Normal Fermi Gas from Collisionless to
   Hydrodynamic Regime
Authors: Shohei Watabe, and Tetsuro Nikuni
Categories: cond-mat.quant-gas
Comments: 19 pages, 9 figures
   The dynamic structure factor of a normal Fermi gas is investigated by using
the moment method for the Boltzmann equation. We determine the spectral
function at finite temperatures over the full range of crossover from the
collisionless regime to the hydrodynamic regime. We find that the Brillouin
peak in the dynamic structure factor exhibits a smooth crossover from zero to
first sound as functions of temperature and interaction strength. The dynamic
structure factor obtained using the moment method also exhibits a definite
Rayleigh peak ($/omega /sim 0$), which is a characteristic of the hydrodynamic
regime. We compare the dynamic structure factor obtained by the moment method
with that obtained from the hydrodynamic equations.
\\ ( http://arxiv.org/abs/1006.5540 , 215kb)
Date: Tue, 29 Jun 2010 13:58:59 GMT (780kb)

Title: Efficient Two-dimensional Subrecoil Raman Cooling of Atoms in a Tripod
Authors: Vladimir S. Ivanov, Yuri V. Rozhdestvensky, and Kalle-Antti Suominen
Categories: physics.atom-ph
Comments: 11 pages, 3 figures
   We present an efficient method for subrecoil cooling of neutral atoms by
applying Raman cooling in 2D to a four-level tripod-system. The atoms can be
cooled simultaneously in two directions using only three laser beams. We
describe the cooling process with a simple model showing that the momentum
distribution can be rapidly narrowed to velocity spread down to
$0.1v_\text{rec}$, corresponding to effective temperature equal to
$0.01T_\text{rec}$. This method opens new possibilities for cooling of neutral
\\ ( http://arxiv.org/abs/1006.5618 , 780kb)
arXiv:1006.5642 (*cross-listing*)
Date: Tue, 29 Jun 2010 14:56:05 GMT (282kb,D)

Title: Sympathetic cooling of rovibrationally state-selected molecular ions
Authors: Xin Tong, Alexander H. Winney, Stefan Willitsch
Categories: physics.chem-ph cond-mat.quant-gas physics.atom-ph
   We present a new method for the generation of rotationally and vibrationally
state-selected, translationally cold molecular ions in ion traps. Our technique
is based on the state-selective threshold photoionization of neutral molecules
followed by sympathetic cooling of the resulting ions with laser-cooled calcium
ions. Using N$_2^+$ ions as a test system, we achieve > 90 % selectivity in the
preparation of the ground rovibrational level and state lifetimes on the order
of 15 minutes limited by collisions with background-gas molecules. The
technique can be employed to produce a wide range of apolar and polar molecular
ions in the ground and excited rovibrational states. Our approach opens up new
perspectives for cold quantum-controlled ion-molecule-collision studies,
frequency-metrology experiments with state-selected molecular ions and
molecular-ion qubits.
\\ ( http://arxiv.org/abs/1006.5642 , 282kb)
Date: Tue, 29 Jun 2010 16:16:17 GMT (183kb)

Title: Topological matter with collective encoding and Rydberg blockade
Authors: Anne E. B. Nielsen and Klaus M{\o}lmer
Categories: quant-ph
Comments: 8 pages, 3 figures
   We propose to use a permutation symmetric sample of multi-level atoms to
simulate the properties of topologically ordered states. The Rydberg blockade
interaction is used to prepare states of the sample which are equivalent to
resonating valence bond states, Laughlin states, and string-net condensates and
to create and study the properties of their quasi-particle-like fundamental
\\ ( http://arxiv.org/abs/1006.5664 , 183kb)
Date: Wed, 30 Jun 2010 08:39:26 GMT (25kb)

Title: Effective Hamiltonian study of excitations in a boson- fermion mixture
   with attraction between components
Authors: A.M. Belemuk, V.N. Ryzhov
Categories: cond-mat.quant-gas
Comments: 9 pages, 5 figures
   An effective Hamiltonian for the Bose subsystem in the mixture of ultracold
atomic clouds of bosons and fermions with mutual attractive interaction is used
for investigating collective excitation spectrum. The ground state and mode
frequencies of the $^{87}$Rb and $^{40}$K mixture are analyzed quantitatively
at zero temperature. We find analytically solutions of the hydrodynamics
equations in the Thomas- Fermi approximation. We discuss the relation between
the onset of collapse and collective modes softening and the dependence of
collective oscillations on scattering length and number of boson atoms.
\\ ( http://arxiv.org/abs/1006.5805 , 25kb)
Date: Wed, 30 Jun 2010 10:03:30 GMT (73kb)

Title: A refined Bogoliubov-Huang approach to helium II thermodynamics
Authors: Jan Ma\'ckowiak, Dawid Borycki
Categories: cond-mat.stat-mech
Comments: 19 pages, 7 figures
   The thermodynamics of a free Bose gas with effective temperature scale
$\tilde{T}$ and hard-sphere Bose gas with the $\tilde{T}$ scale are studied.
$\tilde{T}$ arises as the temperature experienced by a single particle in a
quantum gas with 2-body harmonic oscillator interaction $V_\textrm{osc}$, which
at low temperatures is expected to simulate, almost correctly, the attractive
part of the interatomic potential $V_\textrm{He}$ between $^{4}\textrm{He}$
atoms. The repulsive part of $V_\textrm{He}$ is simulated by a hard-sphere (HS)
potential. The resulting system of HS bosons, with the $\tilde{T}$ temperature
scale (HSET), yields good agreement of heat capacity $C_V(T)$ with the
$T<T_\lambda$ branch of experimental $C_V(T)$ $\lambda$-graph observed in
$^{4}\textrm{He}$ and the theoretical BEC transition temperature equals
$T_\lambda=2.17\,\textrm{K}$. Other thermal properties of HSET agree
qualitatively with those of $^{4}\textrm{He}$, but improve those of the free
Bose gas.
\\ ( http://arxiv.org/abs/1006.5825 , 73kb)
Date: Wed, 30 Jun 2010 12:17:03 GMT (1086kb)

Title: Topological Excitations in Spinor Bose-Einstein Condensates
Authors: Yuki Kawaguchi, Michikazu Kobayashi, Muneto Nitta, Masahito Ueda
Categories: cond-mat.quant-gas hep-ph
Comments: Proceedings of the workshop "New Frontiers in QCD 2010"
   A rich variety of order parameter manifolds of multicomponent Bose-Einstein
condensates (BECs) admit various kinds of topological excitations, such as
fractional vortices, monopoles, skyrmions, and knots. In this paper, we discuss
two topological excitations in spinor BECs: non-Abelian vortices and knots.
Unlike conventional vortices, non-Abelian vortices neither reconnect themselves
nor pass through each other, but create a rung between them in a topologically
stable manner. We discuss the collision dynamics of non-Abelian vortices in the
cyclic phase of a spin-2 BEC. In the latter part, we show that a knot, which is
a unique topological object characterized by a linking number or a Hopf
invariant [$\pi_3 (S^2)=Z$], can be created using a conventional quadrupole
magnetic field in a cold atomic system.
\\ ( http://arxiv.org/abs/1006.5839 , 1086kb)
Date: Wed, 30 Jun 2010 20:02:27 GMT (740kb)

Title: Fermi-Hubbard physics with atoms in an optical lattice
Authors: Tilman Esslinger
Categories: cond-mat.quant-gas
Comments: Posted with permission from the Annual Review of of Condensed Matter
   Physics Volume 1 \c{opyright} 2010 by Annual Reviews,
   The Fermi-Hubbard model is a key concept in condensed matter physics and
provides crucial insights into electronic and magnetic properties of materials.
Yet, the intricate nature of Fermi systems poses a barrier to answer important
questions concerning d-wave superconductivity and quantum magnetism. Recently,
it has become possible to experimentally realize the Fermi-Hubbard model using
a fermionic quantum gas loaded into an optical lattice. In this atomic approach
to the Fermi-Hubbard model the Hamiltonian is a direct result of the optical
lattice potential created by interfering laser fields and short-ranged
ultracold collisions. It provides a route to simulate the physics of the
Hamiltonian and to address open questions and novel challenges of the
underlying many-body system. This review gives an overview of the current
efforts in understanding and realizing experiments with fermionic atoms in
optical lattices and discusses key experiments in the metallic,
band-insulating, superfluid and Mott-insulating regimes.
\\ ( http://arxiv.org/abs/1007.0012 , 740kb)
arXiv:1007.0049 (*cross-listing*)
Date: Wed, 30 Jun 2010 23:49:59 GMT (12kb)

Title: Classical phase-space approach for coherent matter waves
Authors: Fran\c{c}ois Impens and David Gu\'ery-Odelin
Categories: cond-mat.quant-gas quant-ph
Comments: 5 pages, no figures. Final version
Journal-ref: Phys. Rev. A 81, 065602 (2010)
   We investigate a classical phase-space approach of matter-wave propagation
based on the Truncated Wigner Equation (TWE). We show that such description is
suitable for ideal matter waves in quadratic time-dependent confinement as well
as for harmonically trapped Bose Einstein condensates in the Thomas-Fermi
regime. In arbitrary interacting regimes, the TWE combined with the moment
method yields the low-energy spectrum of a condensate as predicted by
independent variational methods. TWE also gives the right breathing mode
frequency for long-ranged interactions decaying as $1/r^2$ in 3D and for a
contact potential in 2D. Quantum signatures, beyond the TWE, may only be found
in the condensate dynamics beyond the regimes of classical phase-space
propagation identified here.
\\ ( http://arxiv.org/abs/1007.0049 , 12kb)
arXiv:1007.0059 (*cross-listing*)
Date: Thu, 1 Jul 2010 02:31:41 GMT (1373kb,D)

Title: Suppression of collisional shifts in a strongly interacting lattice
Authors: Matthew D. Swallows, Michael Bishof, Yige Lin, Sebastian Blatt,
   Michael J. Martin, Ana Maria Rey, and Jun Ye
Categories: quant-ph cond-mat.quant-gas physics.atom-ph
Comments: 15 pages, 5 figures
   Atomic clocks based on neutral atoms confined in optical lattices provide a
unique opportunity for precise studies of quantum many-body systems. The 87Sr
optical lattice clock at JILA has reached an overall fractional frequency
uncertainty of 1x10^-16 [1, 2]. This uncertainty is dominated by two
contributions: atomic collisions and frequency shifts due to room-temperature
blackbody radiation. The density-dependent frequency shift arises from
collisions between fermionic atoms that are subject to slightly inhomogeneous
optical excitation [3, 4]. Several theories of the underlying frequency shift
mechanism have been proposed [5-7]. A three-dimensional optical lattice clock,
where each lattice site contains at most one atom, has been reported [8], and
its collisional shift has been characterized with an uncertainty of 7x10^-16.
Here we present a different and seemingly paradoxical solution to the problem:
by strongly confining atoms in an array of quasi-one-dimensional potentials
formed by a two-dimensional optical lattice, we dramatically increase the
strength of atomic interactions. Instead of an increased collisional shift, we
find that shifts are suppressed in lattice sites containing N > 1 atoms. Strong
interactions introduce an energy gap into the system, and evolution into a
many-body state in which collisions can occur is suppressed. We demonstrate the
effectiveness of this approach by reducing the density-dependent frequency
shift of the JILA lattice clock to the level of 10^-17, reducing the frequency
shift and its uncertainty by more than a factor of ten [1]. This result
demonstrates precise control of interactions in a quantum many-body system,
removing an important obstacle to building optical atomic clocks with large
ensembles of neutral atoms.
\\ ( http://arxiv.org/abs/1007.0059 , 1373kb)
Date: Thu, 1 Jul 2010 06:04:37 GMT (15kb)

Title: Particle creation in Bose--Einstein condensates: Theoretical formulation
   based on conserving gapless mean field theory
Authors: Yasunari Kurita, Michikazu Kobayashi, Hideki Ishihara, Makoto Tsubota
Categories: cond-mat.quant-gas gr-qc
Comments: 9 pages
   We formulate particle creation phenomena in Bose--Einstein condensates in
terms of conserving gapless mean field theory for weakly interacting Bose
gases. The particle creation spectrum is calculated by rediagonalizing the
Bogoliubov--de Gennes (BdG) Hamiltonian in mean field theory. The conservation
implies that quasiparticle creation is accompanied by quantum backreaction to
the condensates. Particle creation in this mean field theory is found to be
equivalent to that in quantum field theory (QFT) in curved spacetime. An
expression is obtained for an effective metric affected by quantum
backreaction. The formula for the particle creation spectrum obtained in terms
of QFT in curved spacetime is shown to be the same as that given by
rediagonalizing the BdG Hamiltonian.
\\ ( http://arxiv.org/abs/1007.0073 , 15kb)
arXiv:1007.0100 (*cross-listing*)
Date: Thu, 1 Jul 2010 08:30:33 GMT (103kb)

Title: Decoherence effects in Bose-Einstein condensate interferometry. I
   General Theory
Authors: B. J. Dalton
Categories: cond-mat.quant-gas quant-ph
Comments: Full version of paper, including all Appendices. Journal version only
   includes Appendix A
   The present paper outlines a basic theoretical treatment of decoherence and
dephasing effects in interferometry based on single component BEC in double
potential wells, where two condensate modes may be involved. Results for both
two mode condensates and the simpler single mode condensate case are presented.
A hybrid phase space distribution functional method is used where the
condensate modes are described via a truncated Wigner representation, and the
basically unoccupied non-condensate modes are described via a positive P
representation. The Hamiltonian for the system is described in terms of quantum
field operators for the condensate and non-condensate modes. The functional
Fokker-Planck equation for the double phase space distribution functional is
derived. Equivalent Ito stochastic equations for the condensate and
non-condensate fields that replace the field operators are obtained, and
stochastic averages of products of these fields give the quantum correlation
functions used to interpret interferometry experiments. The stochastic field
equations are the sum of a deterministic term obtained from the drift vector in
the functional Fokker-Planck equation, and a noise field whose stochastic
properties are determined from the diffusion matrix in the functional
Fokker-Planck equation. The noise field stochastic properties are similar to
those for Gaussian-Markov processes in that the stochastic averages of odd
numbers of noise fields are zero and those for even numbers of noise field
terms are sums of products of stochastic averages associated with pairs of
noise fields. However each pair is represented by an element of the diffusion
matrix rather than products of the noise fields themselves. The treatment
starts from a generalised mean field theory for two condensate mode. The
generalized mean field theory solutions are needed for calculations using the
Ito stochastic field equations.
\\ ( http://arxiv.org/abs/1007.0100 , 103kb)
Date: Thu, 1 Jul 2010 10:04:58 GMT (2302kb)

Title: Cavity QED with an ultracold ensemble on a chip: observing strong
   magnetic coupling at finite temperatures
Authors: Kathrin Henschel, Helmut Ritsch, Johannes Majer and J\"org
Categories: quant-ph
Comments: 20 pages, 18 figures
   We study the nonlinear dynamics of an ensemble of cold trapped atoms with a
hyperfine transition magnetically coupled to a resonant microwave cavity mode.
Despite the minute single atom coupling one obtains strong coupling between
collective hyperfine qubits and microwave photons enabling coherent transfer of
an excitation between the long lived atomic qubit state and the mode. Evidence
of strong coupling can be obtained from the cavity transmission spectrum even
at finite thermal photon number. The system allows to study further prominent
collective phenomena as superradiant decay of an inverted ensemble or building
a narrowband stripline micromaser locked to an atomic hyperfine transition.
\\ ( http://arxiv.org/abs/1007.0116 , 2302kb)
arXiv:1007.0153 (*cross-listing*)
Date: Thu, 1 Jul 2010 12:53:54 GMT (379kb)

Title: Simulating pasta phases by molecular dynamics and cold atoms ---
   Formation in supernovae and superfluid neutrons in neutron stars
Authors: Gentaro Watanabe
Categories: nucl-th astro-ph.SR cond-mat.quant-gas
Comments: 6 pages, 2 figures, to appear in Proceedings of the workshop "New
   Frontiers in QCD 2010" (NFQCD2010)
   In dense stars such as collapsing cores of supernovae and neutron stars,
nuclear "pasta" such as rod-like and slab-like nuclei are speculated to exist.
However, whether or not they are actually formed in supernova cores is still
unclear. Here we solve this problem by demonstrating that a lattice of rod-like
nuclei is formed from a bcc lattice by compression. We also find that the
formation process is triggered by an attractive force between nearest neighbor
nuclei, which starts to act when their density profile overlaps, rather than
the fission instability. We also discuss the connection between pasta phases in
neutron star crusts and ultracold Fermi gases.
\\ ( http://arxiv.org/abs/1007.0153 , 379kb)
Date: Thu, 1 Jul 2010 13:24:58 GMT (1073kb)

Title: Properties of Vacancy Formation in He-4 hcp Crystals at Zero Temperature
   and Fixed Pressure
Authors: Y. Lutsyshyn, C. Cazorla, G. E. Astrakharchik, and J. Boronat
Categories: cond-mat.other
   Equation of state of He-4 hcp crystals with vacancies is determined at zero
temperature using the diffusion Monte Carlo technique, an exact ground state
zero-temperature method. This allows us to extract the formation enthalpy and
isobaric formation energy of a single vacancy in otherwise perfect helium
solid. Results were obtained for pressures up to 160 bar. The isobaric
formation energy is found to reach a minimum near 57 bar where it is equal to
$10.5\pm 1.2$ K. At the same pressure, the vacancy formation volume exhibits a
maximum and reaches the volume of the unit cell. This pressure coincides with
the pressure interval over which a peak in the supersolid fraction of He-4 was
observed in a recent experiment.
\\ ( http://arxiv.org/abs/1007.0161 , 1073kb)

The replacements:

replaced with revised version Fri, 25 Jun 2010 05:43:26 GMT (344kb)

Title: Thermodynamics analogue for self-trapped spinning-stationary Madelung
Authors: Agung Budiyono
Categories: quant-ph
Comments: changed content, Revtex 17 pages
\\ ( http://arxiv.org/abs/quant-ph/0601212 , 344kb)
replaced with revised version Fri, 25 Jun 2010 07:07:59 GMT (248kb)

Title: Hyper-Ramsey Spectroscopy of Optical Clock Transitions
Authors: V. I. Yudin, A. V. Taichenachev, C. W. Oates, Z. W. Barber, N. D.
   Lemke, A. D. Ludlow, U. Sterr, Ch. Lisdat, and F. Riehle
Categories: physics.atom-ph physics.optics
Comments: 5 pages, 4 figures
\\ ( http://arxiv.org/abs/0910.5948 , 248kb)
replaced with revised version Sun, 27 Jun 2010 08:26:23 GMT (810kb,D)

Title: Bogoliubov Theory and Lee-Huang-Yang Corrections in Spin-1 and Spin-2
   Bose-Einstein Condensates in the Presence of the Quadratic Zeeman Effect
Authors: Shun Uchino, Michikazu Kobayashi, and Masahito Ueda
Categories: cond-mat.quant-gas nucl-th
Comments: v3: 62 pages, 18 figures
Journal-ref: Phys. Rev. A 81, 063632 (2010)
DOI: 10.1103/PhysRevA.81.063632
\\ ( http://arxiv.org/abs/0912.0355 , 810kb)
replaced with revised version Mon, 28 Jun 2010 03:22:38 GMT (478kb,D)

Title: Universal behavior of pair correlations in a strongly interacting Fermi
Authors: E. D. Kuhnle, H. Hu, X.-J. Liu, P. Dyke, M. Mark, P. D. Drummond, P.
   Hannaford, and C. J. Vale
Categories: cond-mat.quant-gas
Comments: Manuscript revised, 4 pages, 3 figures
\\ ( http://arxiv.org/abs/1001.3200 , 478kb)
replaced with revised version Mon, 28 Jun 2010 14:20:26 GMT (1652kb)

Title: Groundstate and Collective Modes of a Spin-Polarized Dipolar
   Bose-Einstein Condensate in a Harmonic Trap
Authors: I. Sapina, T. Dahm and N. Schopohl
Categories: cond-mat.quant-gas cond-mat.other
Comments: Changes to previous version: Fig. 7 and Fig. 8 re-plotted in
   compatible pdf-format and one reference added (Ref. [7])
\\ ( http://arxiv.org/abs/1006.4734 , 1652kb)
replaced with revised version Mon, 28 Jun 2010 14:45:16 GMT (60kb)

Title: Numerical solution of the Boltzmann equation for the collective modes of
   trapped Fermi gases
Authors: T.Lepers, D.Davesne, S.Chiacchiera and M.Urban
Categories: cond-mat.quant-gas nucl-th
Comments: 13 pages, 8 figures, accepted for publication in Phys. Rev. A
\\ ( http://arxiv.org/abs/1004.5241 , 60kb)
replaced with revised version Mon, 28 Jun 2010 16:05:15 GMT (513kb)

Title: Comparison between two mobile absolute gravimeters: optical versus
   atomic interferometers
Authors: S. Merlet, Q. Bodart, N. Malossi, A. Landragin, F. Pereira Dos Santos,
   O. Gitlein, L. Timmen
Categories: physics.atom-ph physics.geo-ph
Journal-ref: Metrologia 47 (2010) L9-L11
DOI: 10.1088/0026-1394/47/4/L01
\\ ( http://arxiv.org/abs/1005.0357 , 513kb)
replaced with revised version Mon, 28 Jun 2010 21:10:10 GMT (256kb)

Title: The Nonlinear Dirac Equation in Bose-Einstein Condensates: Relativistic
   Linear Stability Equations, Nonlinear Localized Modes, and Cherenkov
Authors: L. H. Haddad and L. D. Carr
Categories: cond-mat.quant-gas math-ph math.MP
Comments: 5 pages, 2 figures
\\ ( http://arxiv.org/abs/1006.3893 , 256kb)
replaced with revised version Tue, 29 Jun 2010 12:17:16 GMT (460kb,D)

Title: Resonant Superfluidity in an Optical Lattice
Authors: I. Titvinidze, M. Snoek and W. Hofstetter
Categories: cond-mat.quant-gas cond-mat.other
Comments: 19 pages, 3 figures
Journal-ref: New J. Phys. 12 (2010) 065030
DOI: 10.1088/1367-2630/12/6/065030
\\ ( http://arxiv.org/abs/0912.1589 , 460kb)
replaced with revised version Tue, 29 Jun 2010 21:39:35 GMT (137kb)

Title: Interacting Hofstadter spectrum of atoms in an artificial gauge field
Authors: Stephen Powell, Ryan Barnett, Rajdeep Sensarma, Sankar Das Sarma
Categories: cond-mat.quant-gas
Comments: 4+ pages, 2 figures; v2: published version
Journal-ref: Phys. Rev. Lett. 104, 255303 (2010)
DOI: 10.1103/PhysRevLett.104.255303
\\ ( http://arxiv.org/abs/1004.0701 , 137kb)
replaced with revised version Thu, 1 Jul 2010 14:57:20 GMT (847kb)

Title: Nonequivalence of ensembles in the Curie-Weiss anisotropic quantum
   Heisenberg model
Authors: Michael Kastner
Categories: cond-mat.stat-mech cond-mat.quant-gas
Comments: 23 pages, 3 figures
Journal-ref: J. Stat. Mech. (2010) P07006
DOI: 10.1088/1742-5468/2010/07/P07006
\\ ( http://arxiv.org/abs/1005.5050 , 847kb)
replaced with revised version Thu, 1 Jul 2010 17:24:40 GMT (478kb)

Title: Unconventional magnetism in imbalanced Fermi systems with magnetic
   dipolar interactions
Authors: Benjamin M. Fregoso and Eduardo Fradkin
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 10 pages, 6 figures(2 subfigures); 4 appendices. Version published in
   Physical Review B
Journal-ref: Phys. Rev. B 81, 214443 (2010) [9 pages]
DOI: 10.1103/PhysRevB.81.214443
\\ ( http://arxiv.org/abs/1001.4167 , 478kb)

Till next time,

Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           www.physics.uq.edu.au/people/mdavis/
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
Legal stuff: Unless stated otherwise, this e-mail represents only the
views of the sender and not the views of the University of Queensland
Matts-arxiv mailing list
Received on Wed Sep 01 2010 - 11:01:37 EST

This archive was generated by hypermail 2.2.0 : Wed Sep 01 2010 - 11:01:48 EST