[Matts-arxiv] Matt's arXiv selection: week ending 22 May 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Tue, 23 Jun 2009 08:44:08 +1000

Dear subscribers,

Today's mailing was collated by Jacopo Sabbatini. There are 16 new preprints
and 6 replacements:

Date: Fri, 15 May 2009 18:32:08 GMT (59kb)

Title: Stabilization of the p-wave superfluid state in an optical lattice
Authors: Y.-J. Han, Y.-H. Chan, W. Yi, A. J. Daley, S. Diehl, P. Zoller and
   L.-M. Duan
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 5 pages, 5 figures
   It is hard to stabilize the p-wave superfluid state of cold atomic gas in
free space due to inelastic collisional losses. We consider the p-wave Feshbach
resonance in an optical lattice, and show that it is possible to have a stable
p-wave superfluid state where the multi-atom collisional loss is suppressed
through the quantum Zeno effect. We derive the effective Hamiltonian for this
system, and calculate its phase diagram in a one-dimensional optical lattice.
The results show rich phase transitions between the p-wave superfluid state and
different types of insulator states induced either by interaction or by
\\ ( http://arxiv.org/abs/0905.2600 , 59kb)
Date: Mon, 18 May 2009 17:56:58 GMT (1128kb)

Title: Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms
Authors: A. V. Gorshkov, M. Hermele, V. Gurarie, C. Xu, P. S. Julienne, J. Ye,
   P. Zoller, E. Demler, M. D. Lukin, A. M. Rey
Categories: cond-mat.quant-gas
Comments: 12 pages, 6 figures
   Fermionic alkaline-earth(-like) atoms -- atoms with two valence electrons --
such as 87Sr and 171Yb, have unique properties that make them attractive
candidates for the realization of novel atomic clocks and degenerate quantum
gases. At the same time, they are attracting considerable theoretical attention
in the context of quantum information processing. Here we demonstrate that when
such atoms are loaded in optical lattices, they can be used as quantum
simulators of unique many-body phenomena. In particular, we show that the
decoupling of the nuclear spin from the electronic angular momentum can be used
to implement many-body systems with an unprecedented degree of symmetry,
characterized by the SU(N) group with N as large as 10. Moreover, the interplay
of the nuclear spin with the electronic degree of freedom provided by a stable
optically excited state allows for the study of spin-orbital physics. Such
systems may provide valuable insights into strongly correlated physics of
transition metal oxides, heavy fermion materials, and spin liquid phases.
Experimental techniques for preparing and detecting the resulting phases are
\\ ( http://arxiv.org/abs/0905.2610 , 1128kb)
Date: Sun, 17 May 2009 18:04:48 GMT (575kb)

Title: Quantum turbulence at finite temperature: the two-fluids cascade
Authors: Philippe-Emmanuel P.-E. Roche (NEEL), Carlo F. Barenghi, Emmanuel
   L\'ev\^eque (Phys-ENS)
Categories: cond-mat.other
   To model isotropic homogeneous quantum turbulence in superfluid helium, we
have performed Direct Numerical Simulations (DNS) of two fluids (the normal
fluid and the superfluid) coupled by mutual friction. We have found evidence of
strong locking of superfluid and normal fluid along the turbulent cascade, from
the large scale structures where only one fluid is forced down to the vorticity
structures at small scales. We have determined the residual slip velocity
between the two fluids, and, for each fluid, the relative balance of inertial,
viscous and friction forces along the scales. Our calculations show that the
classical relation between energy injection and dissipation scale is not valid
in quantum turbulence, but we have been able to derive a temperature--dependent
superfluid analogous relation. Finally, we discuss our DNS results in terms of
the current understanding of quantum turbulence, including the value of the
effective kinematic viscosity.
\\ ( http://arxiv.org/abs/0905.2754 , 575kb)
Date: Mon, 18 May 2009 08:37:34 GMT (58kb)

Title: All-optical pump-and-probe detection of dynamical correlations in a
   two-dimensional Fermi gas
Authors: Tung-Lam Dao, Corinna Kollath, Iacopo Carusotto, Michael Koehl
Categories: cond-mat.quant-gas cond-mat.str-el
Comments: 4 pages, 4 figures
   We propose an all-optical scheme to probe the dynamical correlations of a
strongly-interacting gas of ultracold atoms. The proposed technique is based on
a pump-and-probe scheme: a coherent light pulse is initially converted into an
atomic coherence and later retrieved after a variable storage time. The
efficiency of the proposed method to measure the one-particle Green function of
the gas is validated by numerical and analytical calculations of the expected
signal for the two cases of a normal Fermi gas and a BCS superfluid state.
Protocols to extract the superfluid gap and the full quasi-particle dispersions
are discussed.
\\ ( http://arxiv.org/abs/0905.2826 , 58kb)
Date: Mon, 18 May 2009 08:56:49 GMT (13kb)

Title: Mixtures of Bose gases confined in a ring potential
Authors: J. Smyrnakis, G. M. Kavoulakis, M. Magiropoulos, K. K\"arkk\"ainen, S.
   M. Reimann
Categories: cond-mat.quant-gas
Comments: 4 pages, 1 figure
   We examine the ground state and the rotational properties of a mixture of two
distinguishable Bose gases that are confined in a ring potential. Persistent
currents are shown to be stable for a range of the population imbalance between
the two components at low angular momentum. At higher values of the angular
momentum even small admixtures of a second species of atoms make the persistent
currents highly fragile.
\\ ( http://arxiv.org/abs/0905.2832 , 13kb)
Date: Mon, 18 May 2009 11:31:08 GMT (398kb,D)

Title: Fractional photon-assisted tunneling for Bose-Einstein condensates in a
   double well
Authors: Niklas Teichmann, Martin Esmann, and Christoph Weiss
Categories: cond-mat.quant-gas cond-mat.other
Comments: 7 pages, 5 figures
   Half-integer photon-resonances in a periodically shaken double well are
investigated on the level of the N-particle quantum dynamics. Contrary to
non-linear mean-field equations, the linear N-particle Schrodinger equation
does not contain any non-linearity which could be the origin of such
resonances. Nevertheless, analytic calculations on the N-particle level explain
why such resonances can be observed even for particle numbers as low as N = 2.
These calculations also demonstrate why fractional photon resonances are not
restricted to half-integer values.
\\ ( http://arxiv.org/abs/0905.2838 , 398kb)
Date: Sun, 17 May 2009 08:55:31 GMT (14kb)

Title: Schr\"odinger's cat meets Occam's razor
Authors: Richard D. Gill
Categories: quant-ph
   We discuss V.P. Belavkin's approach to the measurement problem encapsulated
in his theory of eventum mechanics (as presented in his 2007 survey). In
particular, we show its relation to ideas based on superselection and
interaction with the environment developed by N.P. Landsman (1995, and more
recent papers).
   Landsman writes "those believing that the classical world exists
intrinsically and absolutely [such persons later termed by him B-realists] are
advised against reading this [his, 1995] paper". He adopts a milder position,
calling it that of an A-realist: we live in a classical world but to give it
special status is like insisting that the Earth is the centre of the universe.
The B-realists are accused of living under some kind of hallucination. Landsman
presents arguments pointing in a particular direction to a resolution of the
measurement problem which at least would satisfy the A-realists. We point out
in this paper that the theory earlier developed by Belavkin (surveyed in his
2007 paper) seems to complete Landsman's program or at least exhibits a
"realisation" satisfying his desiderata. At the same time it seems that this
completion of the program ends up giving both A- and B-realists equal licence
to accuse the others of living under hallucinations.
\\ ( http://arxiv.org/abs/0905.2723 , 14kb)
Date: Mon, 18 May 2009 20:00:07 GMT (1229kb,D)

Title: Observation of elastic doublon decay in the Fermi-Hubbard model
Authors: Niels Strohmaier, Daniel Greif, Robert J\"ordens, Leticia Tarruell,
   Henning Moritz, Tilman Esslinger, Rajdeep Sensarma, David Pekker, Ehud
   Altman, Eugene Demler
Categories: cond-mat.quant-gas cond-mat.str-el
   We investigate the decay of highly excited states of ultracold fermions in a
three-dimensional optical lattice. Starting from a repulsive Fermi-Hubbard
system near half filling, we generate additional doubly occupied sites
(doublons) by lattice modulation. The subsequent relaxation back to thermal
equilibrium is monitored over time. The measured doublon lifetime covers two
orders of magnitude. In units of the tunneling time h/J it is found to depend
exponentially on the ratio of on-site interaction energy U to kinetic energy J.
We argue that the dominant mechanism for the relaxation is a high order
scattering process involving several single fermions as scattering partners. A
many-body calculation is carried out using diagrammatic methods, yielding good
agreement with the data.
\\ ( http://arxiv.org/abs/0905.2963 , 1229kb)
Date: Tue, 19 May 2009 07:23:15 GMT (176kb)

Title: Energy bands and Landau levels of ultracold fermions in the bilayer
   honeycomb optical lattice
Authors: Jing-Min Hou
Categories: cond-mat.quant-gas cond-mat.other
Comments: To appear in Journal of Modern Optics
   We investigate the spectrum and eigenstates of ultracold fermionic atoms in
the bilayer honeycomb optical lattice. In the low energy approximation, the
dispersion relation has parabolic form and the quasiparticles are chiral. In
the presence of the effective magnetic field, which is created for the system
with optical means, the energy spectrum shows an unconventional Landau level
structure. Furthermore, the experimental detection of the spectrum is proposed
with the Bragg scattering techniques.
\\ ( http://arxiv.org/abs/0905.3035 , 176kb)
Date: Tue, 19 May 2009 11:36:14 GMT (8kb)

Title: Generation of nonground-state condensates and adiabatic paradox
Authors: V.I. Yukalov and V.S. Bagnato
Categories: cond-mat.quant-gas cond-mat.mes-hall
Comments: Latex file, 10 pages
Journal-ref: Laser Phys. Lett. 6 (2009) 399-403
   The problem of resonant generation of nonground-state condensates is
addressed aiming at resolving the seeming paradox that arises when one resorts
to the adiabatic representation. In this picture, the eigenvalues and
eigenfunctions of a time-dependent Gross-Pitaevskii Hamiltonian are also
functions of time. Since the level energies vary in time, no definite
transition frequency can be introduced. Hence no external modulation with a
fixed frequency can be made resonant. Thus, the resonant generation of
adiabatic coherent modes is impossible. However, this paradox occurs only in
the frame of the adiabatic picture. It is shown that no paradox exists in the
properly formulated diabatic representation. The resonant generation of
diabatic coherent modes is a well defined phenomenon. As an example, the
equations are derived, describing the generation of diabatic coherent modes by
the combined resonant modulation of the trapping potential and atomic
scattering length.
\\ ( http://arxiv.org/abs/0905.3068 , 8kb)
Date: Wed, 20 May 2009 01:14:18 GMT (238kb)

Title: Density-functional theory of two-component Bose gases in one-dimensional
   harmonic traps
Authors: Yajiang Hao, Shu Chen
Categories: cond-mat.str-el cond-mat.quant-gas
Comments: 8 pages, 5 figures
   We investigate the ground-state properties of two-component Bose gases
confined in one-dimensional harmonic traps in the scheme of density-functional
theory. The density-functional calculations employ a Bethe-ansatz-based
local-density approximation for the correlation energy, which accounts for the
correlation effect properly in the full physical regime. For the binary Bose
mixture with spin-independent interaction, the homogeneous reference system is
exactly solvable by the Bethe-ansatz method. Within the local-density
approximation, we determine the density distribution of each component and
study its evolution from Bose distributions to Fermi-like distribution with the
increase in interaction. For the binary mixture of Tonks-Girardeau gases with a
tunable inter-species repulsion, with a generalized Bose-Fermi transformation
we show that the Bose mixture can be mapped into a two-component Fermi gas,
which corresponds to exact soluble Yang-Gaudin model for the homogeneous
system. Based on the ground-state energy function of the Yang-Gaudin model, the
ground-state density distributions are calculated for various inter-species
interactions. It is shown that with the increase in inter-species interaction,
the system exhibits composite-fermionization crossover.
\\ ( http://arxiv.org/abs/0905.3207 , 238kb)
Date: Wed, 20 May 2009 14:23:31 GMT (28kb)

Title: Correlation dynamics of strongly-correlated bosons out of equilibrium
   induced by a lattice time-modulation
Authors: Karen Rodriguez, Arturo Arg\"uelles and Luis Santos
Categories: cond-mat.quant-gas cond-mat.other
Comments: 6 pages, 8 figures
   We analyse by means of Matrix Product States techniques the dynamics of
strongly-correlated Bose gases in a finite one-dimensional optical lattice
during a change of the lattice parameters within the superfluid region. We
analyse different regimes of perturbation, which range from adiabatic to
non-adiabatic. In particular, we are interested in the evolution of the system
correlations on time, showing that the each correlation presents different time
scales in their response to the lattice modulation. As a consequence, when
local quantities have converged, the long-range correlations and the
quasi-condensate fraction may still present a significant dynamics. In
addition, the different time scales for several correlations open the
possibility to have a well defined criterion for adiabaticity in the system.
\\ ( http://arxiv.org/abs/0905.3312 , 28kb)
Date: Wed, 20 May 2009 09:12:21 GMT (230kb)

Title: Pump-probe spectroscopy of two-body correlations in ultracold gases
Authors: Christiane P. Koch, Ronnie Kosloff
Categories: quant-ph cond-mat.quant-gas
   We suggest pump-probe spectroscopy to study pair correlations that determine
the many-body dynamics in weakly interacting, dilute ultracold gases. A
suitably chosen, short laser pulse depletes the pair density locally, creating
a 'hole' in the electronic ground state. The dynamics of this non-stationary
pair density is monitored by a time-delayed probe pulse. The resulting
transient signal allows to spectrally decompose the 'hole' and to map out the
pair correlation functions.
\\ ( http://arxiv.org/abs/0905.3251 , 230kb)
Date: Wed, 20 May 2009 20:00:28 GMT (452kb)

Title: Representation of quantum dynamics of interacting systems through
   classical trajectories
Authors: Anatoli Polkovnikov
Categories: cond-mat.stat-mech cond-mat.quant-gas
Comments: 82 pages (single column), 17 figures
   We formulate representation of quantum dynamics of many-particle interacting
systems through classical trajectories as a perturbative expansion in quantum
fluctuations around the classical limit. We explicitly consider three different
classical limits in the coordinate-momentum representation (corpuscular
classical limit), coherent state representation (wave classical limit), and the
classical limit for spin systems. We describe how one recovers truncated Wigner
approximation (TWA) in the leading order in quantum fluctuations around each of
these limits. Further quantum corrections can be found either in the form of
non-linear response of observables to infinitesimal quantum jumps or
equivalently in terms of stochastic quantum jumps with non-positive weight. We
discuss how one can find both equal and non-equal time correlation functions
within this approach and which correlation functions have casual
representation. Our approach is closely related to phase space methods based on
Weyl quantization, coherent state phase space methods, and Keldysh diagrammatic
technique. We show how both new results and earlier concepts naturally emerge
from combining path-integral approach and the Heisenberg representation. We
illustrate this approach with various examples including sine-Gordon model,
one- and two-dimensional Bose Hubbard model, Dicke model and others.
\\ ( http://arxiv.org/abs/0905.3384 , 452kb)
Date: Thu, 21 May 2009 19:28:15 GMT (328kb)

Title: Evolution of squeezed states under the Fock-Darwin Hamiltonian
Authors: Jaime E. Santos, Nuno M. Peres, Joao Lopes dos Santos
Categories: cond-mat.quant-gas cond-mat.other
   We develop a complete analytical description of the time evolution of
squeezed states of a charged particle under the Fock-Darwin Hamiltonian and a
time-dependent electric field. This result generalises a relation obtained by
Infeld and Pleba\'nski for states of the one-dimensional harmonic oscillator.
We relate the evolution of a state-vector subjected to squeezing to that of
state which is not subjected to squeezing and for which the time-evolution
under the simple harmonic oscillator dynamics is known (e.g. an eigenstate of
the Hamiltonian). A corresponding relation is also established for the Wigner
functions of the states, in view of their utility in the analysis of cold-ion
experiments. In an appendix, we compute the response functions of the FD
Hamiltonian to an external electric field, using the same techniques as in the
main text.
\\ ( http://arxiv.org/abs/0905.3547 , 328kb)
Date: Thu, 21 May 2009 18:20:05 GMT (152kb)

Title: Dispersive propagation of ultraslow light in an atomic Bose-Einstein
Authors: Devrim Tarhan, Seckin Sefi, and Ozgur E. Mustecaplioglu
Categories: physics.optics
Comments: 14 pages, 3 figures
   One dimensional propagation of ultraslow optical pulses in an atomic
Bose-Einstein condensate taking into account the dispersion and the spatial
inhomogeneity is investigated. Analytical and semi-analytical solutions of the
dispersive inhomogeneous wave equation modeling the ultraslow pulse propagation
are developed and compared against the standard wave equation solvers based
upon Cranck-Nicholson and pseudo-spectral methods. The role of curvature of the
trapping potential of the condensate on the amount of dispersion of the
ultraslow pulse is pointed out.
\\ ( http://arxiv.org/abs/0905.3541 , 152kb)

The replacements:

replaced with revised version Fri, 15 May 2009 07:50:09 GMT (211kb)

Title: Nonclassicality in phase space and nonclassical correlation
Authors: Petr Marek, M. S. Kim and Jinhyoung Lee
Categories: quant-ph
Comments: 5 pages, 4 figures, replaced by the published version
Journal-ref: Phys. Rev. A 79, 052315 (2009)
\\ ( http://arxiv.org/abs/0705.3217 , 211kb)
replaced with revised version Sat, 16 May 2009 12:04:35 GMT (35kb,D)

Title: Ground state energy of the two-dimensional weakly interacting Bose gas:
   First correction beyond Bogoliubov theory
Authors: Christophe Mora, Yvan Castin
Categories: cond-mat.stat-mech
Comments: 4 pages, 1 figure, published in Phys. Rev. Lett
Journal-ref: Phys. Rev. Lett. 102, 180404 (2009)
DOI: 10.1103/PhysRevLett.102.180404
\\ ( http://arxiv.org/abs/0901.2943 , 35kb)
replaced with revised version Tue, 19 May 2009 18:28:06 GMT (129kb)

Title: Interference of Bose-Einstein condensates: quantum non-local effects
Authors: William W.J. Mullin (UMASS), Franck Lalo\"e (LKB - Lhomond)
Categories: quant-ph cond-mat.other
Comments: version published in Phys Rev
Journal-ref: Physical Review A: Atomic, Molecular and Optical Physics A78
   (2008) 061605
DOI: 10.1103/PhysRevA.78.061605
\\ ( http://arxiv.org/abs/0805.0105 , 129kb)
replaced with revised version Tue, 19 May 2009 13:49:43 GMT (286kb)

Title: Skyrmion in spinor condensates and its stability in trap potentials
Authors: Akiyuki Tokuno, Yohei Mitamura, Masaki Oshikawa, Igor F. Herbut
Categories: cond-mat.other cond-mat.stat-mech
Comments: 12 pages, 9 figures, final version
Journal-ref: Phys. Rev. A 79, 053626 (2009)
DOI: 10.1103/PhysRevA.79.053626
\\ ( http://arxiv.org/abs/0812.2736 , 286kb)
replaced with revised version Tue, 19 May 2009 07:23:33 GMT (472kb)

Title: Occupation Statistics of a BEC for a Driven Landau-Zener Crossing
Authors: Katrina Smith-Mannschott, Maya Chuchem, Moritz Hiller, Tsampikos
   Kottos, Doron Cohen
Categories: cond-mat.other
Comments: 4 pages, 5 figures
\\ ( http://arxiv.org/abs/0901.2807 , 472kb)
replaced with revised version Mon, 18 May 2009 22:25:28 GMT (18kb)

Title: Ground State Properties of Cold Bosonic Atoms At Large Scattering
Authors: Jun Liang Song, Fei Zhou (UBC)
Categories: cond-mat.other
Comments: 4 pages, 3 figures, accepted by PRL
\\ ( http://arxiv.org/abs/0902.0366 , 18kb)

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
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Received on Fri Jul 31 2009 - 11:19:13 EST

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