Matt's arXiv selection: week ending 18 July 2008

From: Matthew Davis <>
Date: Mon, 04 Aug 2008 10:36:06 +1000

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

Treading water it seems... I'm back home this coming week, then maybe we will
catch up.

This week there were 21 new preprints and 6 replacements:

Date: Fri, 11 Jul 2008 16:37:15 GMT (89kb)

Title: Crystallization of trions in SU(3) cold atom gases trapped in optical
Authors: Rafael A. Molina, Jorge Dukelsky, Peter Schmitteckert
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: 4 pages 6 figures
   Cold Fermionic atoms with three different hyperfine states confined in
optical lattices show pronounced Atomic Density Waves (ADWs). These ADWs are
pinned due to the confining potential that traps the atoms in the optical
lattice and can be considered a crystal of strongly bound trions. We show that
the crystalline phase is incompressible and robust against SU(3) symmetry
breaking interaction. We also show that it is generic in the presence of the
trap due to its incompressible characteristics. A simulation of the time
evolution of the fermionic gas after the trapping potential is switch off shows
that the formation of the trionic crystal is marked by a freezing of the
dynamics in the lattice.
\\ ( , 89kb)
Date: Fri, 11 Jul 2008 05:49:45 GMT (153kb)

Title: Mean-field dynamics of a non-hermitian Bose-Hubbard dimer
Authors: E. M. Graefe, H. J. Korsch and A. E. Niederle
Categories: quant-ph
Comments: 4 pages, 3 figures
   We investigate an N-particle Bose-Hubbard dimer with an additional effective
decay term in one of the sites. A mean-field approximation for this
non-hermitian many-particle system is derived, based on a coherent state
approximation. The properties of the resulting nonlinear, non-hermitian
two-level system are analyzed, in particular the bifurcation scenario showing
characteristic modifications of the self trapping transition. The mean-field
dynamics is found to be in reasonable agreement with the full many-particle
\\ ( , 153kb)
Date: Fri, 11 Jul 2008 18:07:58 GMT (287kb)

Title: Matter--wave emission in optical lattices: Single particle and
   collective effects
Authors: Ines de Vega, Diego Porras, J. Ignacio Cirac
Categories: quant-ph
Comments: 5 pages, 3 figures
   We introduce a simple set--up corresponding to the matter-wave analogue of
impurity atoms embedded in an infinite photonic crystal and interacting with
the radiation field. Atoms in a given internal level are trapped in an optical
lattice, and play the role of the impurities. Atoms in an untrapped level play
the role of the radiation field. The interaction is mediated by means of lasers
that couple those levels. By tuning the lasers parameters, it is possible to
drive the system through different regimes, and observe phenomena like matter
wave superradiance, non-Markovian atom emission, and the appearance of bound
atomic states.
\\ ( , 287kb)
Date: Fri, 11 Jul 2008 18:50:28 GMT (188kb)

Title: Influence of atomic collisions on spectrum of light scattered from an
   f-deformed Bose-Einstein condensate
Authors: Z. Haghshenasfard, M. H. Naderi and M. Soltanolkotabi
Categories: quant-ph
Comments: 17 pages, 4figures
   In this paper, we investigate the spectrum of light scattered from a
Bose-Einstein condensate in the framework of f-deformed boson. We use an
f-deformed quantum model in which the Gardiners phonon operators for BEC are
deformed by an operator-valued function, f(n), of the particle-number operator
n. We consider the collisions between the atoms as a special kind of
f-deformation. The collision rate k is regarded as the deformation parameter
and the spectrum of light scattered from the deformed BEC is analyzed. In
particular, we find that with increasing the values of deformation parameters k
and eta=1/N (N, total number of condensate atoms) the scattering spectrum shows
deviation from the spectrum associated with nondeformed Bose-Einstein
\\ ( , 188kb)
Date: Fri, 11 Jul 2008 18:34:34 GMT (466kb)

Title: The hyperfine energy levels of alkali metal dimers: ground-state polar
   molecules in electric and magnetic fields
Authors: J. Aldegunde, Ben A. Rivington, Piotr S. \.Zuchowski and Jeremy M.
Categories: physics.atom-ph physics.chem-ph
Comments: 8 pages, 6 figures
   We investigate the energy levels of heteronuclear alkali metal dimers in
levels correlating with the lowest rotational level of the ground electronic
state, which are important in efforts to produce ground-state ultracold
molecules. We use density-functional theory to calculate nuclear quadrupole and
magnetic coupling constants for RbK and RbCs and explore the hyperfine
structure in the presence of electric and magnetic fields. For nonrotating
states, the zero-field splittings are dominated by the electron-mediated part
of the nuclear spin-spin coupling. They are a few kHz for RbK isotopologs and a
few tens of kHz for RbCs isotopologs.
\\ ( , 466kb)
Date: Sat, 12 Jul 2008 23:13:34 GMT (162kb)

Title: Effective one-dimensional dynamics of elongated Bose-Einstein
Authors: A. Mu\~noz Mateo and V. Delgado (Univ. La Laguna)
Categories: cond-mat.other
Comments: 10 pages, 5 figures
   By using a variational approach in combination with the adiabatic
approximation we derive a new effective 1D equation of motion for the axial
dynamics of elongated condensates. For condensates with vorticity $|q|=0$ or 1,
this equation coincides with our previous proposal [Phys. Rev. A \textbf{77},
013617 (2008)]. We also rederive the nonpolynomial Schr\"{o}dinger equation
(NPSE) in terms of the adiabatic approximation. This provides a unified
treatment for obtaining the different effective equations and allows to
appreciate clearly the differences and similarities between the various
proposals. We also obtain an expression for the axial healing length of
cigar-shaped condensates and show that, in the local density approximation and
in units of the axial oscillator length, it coincides with the inverse of the
condensate axial half-length. From this result it immediately follows the
necessary condition for the validity of the local density approximation.
Finally, we obtain analytical formulas that give the frequency of the axial
breathing mode with an accuracy better than 1%. These formulas can be relevant
from an experimental point of view since they can be expressed in terms only of
the axial half-length and remain valid in the crossover between the
Thomas-Fermi and the quasi-1D mean-field regimes. We have corroborated the
validity of our results by numerically solving the full 3D Gross-Pitaevskii
\\ ( , 162kb)
Date: Mon, 14 Jul 2008 04:50:29 GMT (8kb)

Title: Wave Function and Pair Distribution Function of a Dilute Bose Gas
Authors: Bo-Bo Wei Chen-Ning Yang
Categories: cond-mat.stat-mech
Comments: 2 pages, 1 figure
   The wave function of a dilute hard sphere Bose gas at low temperatures is
discussed, emphasizing the formation of pairs. The pair distribution function
is calculated for two values of $\sqrt{\rho a^3}$.
\\ ( , 8kb)
Date: Mon, 14 Jul 2008 13:03:37 GMT (215kb)

Title: Exact results of two-component Fermi gas in a hard wall trap
Authors: Bo-Bo Wei, Jun-Peng Cao, Shi-Jian Gu and Hai-Qing Lin
Categories: cond-mat.stat-mech
Comments: 6 pages, 6 pages
   We investigate the ground state properties of a one-dimensional two-component
ultra-cold Fermi gas in an infinite potential well. Exact Bethe ansatz solution
is used to calculate the many-body wave function of the system. Then we
evaluate the single-particle reduced density matrix and two-particle density
density correlations of the system for different interaction strengths. We find
that the momentum density distributions of the strongly interacting
two-component Fermi gas is distinct from that of free spinless Fermi gas
although their position density distributions are similar. This interacting
system may be experimentally accessible using ultra-cold atoms.
\\ ( , 215kb)
Date: Mon, 14 Jul 2008 16:31:07 GMT (32kb)

Title: Internal structure of a quantum soliton and classical excitations due to
   trap opening
Authors: Yvan Castin (LKB - Lhomond)
Categories: cond-mat.other
Comments: 12 pages
   We analytically solve two problems that may be useful in the context of the
recent observation of matter wave bright solitons in a one-dimensional
attractive atomic Bose gas. The first problem is strictly beyond mean field:
   From the Bethe ansatz solution we extract the internal correlation function
of the particle positions in the quantum soliton, that is for a fixed center of
mass position. The second problem is solved in the limit of a large number of
particles, where the mean field theory is asymptotically correct: It deals with
the number of excitations created by the opening of the trap, starting from a
pure soliton in a weakly curved harmonic potential.
\\ ( , 32kb)
Date: Tue, 15 Jul 2008 17:39:18 GMT (223kb)

Title: Damped bounces of an isolated perfect quantum gas
Authors: S. Camalet
Categories: cond-mat.mes-hall
   The issue of the thermalization of an isolated quantum system is addressed by
considering a confined perfect gas. As we are interested in the behavior of
truly isolated systems, we assume the gas is in a pure state of macroscopically
well-defined energy. We show that, for single-particle distributions of a
general many-body system, such a state is strictly equivalent to the
microcanonical mixed state at the same energy. We study the case of a perfect
gas confined by gravity and initially trapped above a certain height. For this
system, we are able to determine the time-dependent density profile in the
limit of a large particle number. The expression obtained depends on the
initial gas state only via a few thermodynamic parameters. Though we consider
non-interacting particles, the gas density relaxes into an asymptotic profile,
but which is not the thermal equilibrium one determined by the gas energy and
particle number. Moreover, we show that this asymptotic density is not modified
by an energy-conserving environment. For a Bose gas below the condensation
temperature, this relaxation behavior is found for the thermal cloud whereas
the condensate evolves in a very different way.
\\ ( , 223kb)
Date: Tue, 15 Jul 2008 18:43:54 GMT (321kb)

Title: Finite temperature coherence of the ideal Bose gas in an optical lattice
Authors: G.A. Muradyan and J.R. Anglin
Categories: cond-mat.stat-mech
   In current experiments with cold quantum gases in periodic potentials,
interference fringe contrast is typically the easiest signal in which to look
for effects of non-trivial many-body dynamics. In order better to calibrate
such measurements, we analyse the background effect of thermal decoherence as
it occurs in the absence of dynamical interparticle interactions. We study the
effect of optical lattice potentials, as experimentally applied, on the
condensed fraction of a non-interacting Bose gas in local thermal equilibrium
at finite temperatures. We show that the experimentally observed decrease of
the condensate fraction in the presence of the lattice can be attributed, up to
a threshold lattice height, purely to ideal gas thermodynamics; conversely we
confirm that sharper decreases in first-order coherence observed in stronger
lattices are indeed attributable to many-body physics. Our results also suggest
that the fringe visibility 'kinks' observed in F.Gerbier et al., Phys. Rev.
Lett. 95, 050404 (2005) may be explained in terms of the competition between
increasing lattice strength and increasing mean gas density, as the gaussian
profile of the red-detuned lattice lasers also increases the effective strength
of the harmonic trap.
\\ ( , 321kb)
Date: Tue, 15 Jul 2008 19:48:26 GMT (132kb)

Title: Dislocation-Mediated Melting in Superfluid Vortex Lattices
Authors: S. Andrew Gifford and Gordon Baym
Categories: cond-mat.stat-mech cond-mat.mes-hall
Comments: 9 pages, 2 figures
   We describe thermal melting of the two-dimensional vortex lattice in a
rotating superfluid by generalizing the Halperin and Nelson theory of
dislocation-mediated melting. and derive a melting temperature proportional to
the renormalized shear modulus of the vortex lattice. The rigid-body rotation
of the superfluid attenuates the effects of lattice compression on the energy
of dislocations and hence the melting temperature, while not affecting the
shearing. Finally, we discuss dislocations and thermal melting in inhomogeneous
rapidly rotating Bose-Einstein condensates; we delineate a phase diagram in the
temperature -- rotation rate plane, and infer that the thermal melting
temperature should lie below the Bose-Einstein transition temperature.
\\ ( , 132kb)
Date: Tue, 15 Jul 2008 11:37:58 GMT (633kb,D)

Title: Cavity Opto-Mechanics with a Bose-Einstein Condensate
Authors: Ferdinand Brennecke, Stephan Ritter, Tobias Donner, Tilman Esslinger
Categories: quant-ph
Comments: F.B. and S.R. contributed equally to this work. 6 pages, 4 figures
   Cavity opto-mechanics studies the coupling between a mechanical oscillator
and a cavity field, with the aim to shed light on the border between classical
and quantum physics. Here we report on a cavity opto-mechanical system in which
a collective density excitation of a Bose-Einstein condensate is shown to serve
as the mechanical oscillator coupled to the cavity field. We observe that a few
photons inside the ultrahigh-finesse cavity trigger a strongly driven
back-action dynamics, in quantitative agreement with a cavity opto-mechanical
model. With this experiment we approach the strong coupling regime of cavity
opto-mechanics, where a single excitation of the mechanical oscillator
significantly influences the cavity field. The work opens up new directions to
investigate mechanical oscillators in the quantum regime and quantum gases with
non-local coupling.
\\ ( , 633kb)
Date: Wed, 16 Jul 2008 16:16:29 GMT (121kb)

Title: Bragg spectroscopy of a strongly interacting Bose-Einstein condensate
Authors: J. J. Kinnunen and M. J. Holland
Categories: cond-mat.other cond-mat.stat-mech
Comments: 11 pages, 4 figures
   We study Bragg spectroscopy of a strongly interacting Bose-Einstein
condensate using time-dependent Hartree-Fock-Bogoliubov theory. We include
approximatively the effect of the momentum dependent scattering amplitude which
is shown to be the dominant factor in determining the spectrum for large
momentum Bragg scattering. The condensation of the Bragg scattered atoms is
shown to significantly alter the observed excitation spectrum by creating a
novel pairing channel of mobile pairs.
\\ ( , 121kb)
Date: Tue, 15 Jul 2008 21:10:54 GMT (932kb)

Title: Measuring measurement
Authors: J.S. Lundeen, A. Feito, H. Coldenstrodt-Ronge, K.L. Pregnell, Ch.
   Silberhorn, T.C. Ralph, J. Eisert, M.B. Plenio, I.A. Walmsley
Categories: quant-ph
Comments: 6 pages, 4 figures
   Measurement connects the world of quantum phenomena to the world of classical
events. It plays both a passive role, observing quantum systems, and an active
one, preparing quantum states and controlling them. Surprisingly - in the light
of the central status of measurement in quantum mechanics - there is no general
recipe for designing a detector that measures a given observable. Compounding
this, the characterization of existing detectors is typically based on partial
calibrations or elaborate models. Thus, experimental specification (i.e.
tomography) of a detector is of fundamental and practical importance. Here, we
present the realization of quantum detector tomography: we identify the optimal
positive-operator-valued measure describing the detector, with no ancillary
assumptions. This result completes the triad, state, process, and detector
tomography, required to fully specify an experiment. We characterize an
avalanche photodiode and a photon number resolving detector capable of
detecting up to eight photons. This creates a new set of tools for accurately
detecting and preparing non-classical light.
\\ ( , 932kb)
Date: Wed, 16 Jul 2008 07:01:12 GMT (357kb)

Title: Simulations and Experiments on Polarisation Squeezing in Optical Fibre
Authors: Joel F. Corney, Joel Heersink, Ruifang Dong, Vincent Josse, Peter D.
   Drummond, Gerd Leuchs and Ulrik L. Andersen
Categories: quant-ph
Comments: 19 pages, lots of figures
   We investigate polarisation squeezing of ultrashort pulses in optical fibre,
over a wide range of input energies and fibre lengths. Comparisons are made
between experimental data and quantum dynamical simulations, to find good
quantitative agreement. The numerical calculations, performed using both
truncated Wigner and exact $+P$ phase-space methods, include nonlinear and
stochastic Raman effects, through coupling to phonons variables. The
simulations reveal that excess phase noise, such as from depolarising GAWBS,
affects squeezing at low input energies, while Raman effects cause a marked
deterioration of squeezing at higher energies and longer fibre lengths. The
optimum fibre length for maximum squeezing is also calculated.
\\ ( , 357kb)
Date: Wed, 16 Jul 2008 14:55:39 GMT (125kb)

Title: Refractive Index Enhancement with Vanishing Absorption in an Atomic
Authors: N. A. Proite, B. E. Unks, J. T. Green, and D. D. Yavuz
Categories: quant-ph physics.optics
Comments: 11 pages, 4 figures
   We report a proof-of-principle experiment where the refractive index of an
atomic vapor is enhanced while maintaining vanishing absorption of the beam.
The key idea is to drive alkali atoms in a vapor with appropriate control
lasers and induce a gain resonance and an absorption resonance for a probe beam
in a two-photon Raman configuration. The strength and the position of these two
resonances can be manipulated by changing the parameters of the control lasers.
By using the interference between these two resonances, we obtain an enhanced
refractive index without an increase in the absorption.
\\ ( , 125kb)
Date: Wed, 16 Jul 2008 15:57:30 GMT (2342kb,D)

Title: Power-law behavior in the quantum-resonant evolution of the delta-kicked
Authors: P. L. Halkyard, M. Saunders, S. A. Gardiner, K. J. Challis
Categories: physics.atom-ph
Comments: 17 pages, 5 figures
   We consider the atom-optical delta-kicked accelerator when the initial
momentum distribution is symmetric. We demonstrate the existence of
quantum-resonant dynamics, and derive analytic expressions for the system
evolution. In particular, we consider the dynamical evolution of the momentum
moments and find that all even-ordered momentum moments exhibit a power law
growth. In the ultracold (zero-temperature) limit the exponent is determined by
the order of the moment, whereas for a broad, thermal initial momentum
distribution the exponent is reduced by one. To demonstrate the power law
behavior explicitly we consider the evolution of the second- and fourth-order
momentum moment, and cumulant, for both an initially uniform momentum
distribution, and an initially Gaussian momentum distribution.
\\ ( , 2342kb)
Date: Thu, 17 Jul 2008 13:51:09 GMT (70kb)

Title: The Bifurcation Theory of Magnetic Monopoles in a Charged Two-Condensate
   Bose-Einstein System
Authors: Shu-Fan Mo, Ji-Rong Ren, and Tao Zhu
Categories: cond-mat.supr-con
Comments: 21 pages, 5 figures
Journal-ref: J. Phys. A: Math. Theor. 41, 315214 (2008)
DOI: 10.1088/1751-8113/41/31/315214
   Magnetic monopoles, that are particle-like field configurations with which
one can associate a topological charge, widely exist in various three
dimensional condensate systems. In this paper, by making use of \emph{Duan}'s
topological current theory, we obtain the charge density of magnetic monopoles
and their bifurcation theory in a charged two condensate Bose-Einstein system.
The evolution of magnetic monopoles is studied from the topological properties
of a three-dimensional vector field. The magnetic monopoles are found
generating or annihilating at the limit points and encountering, splitting, or
merging at the bifurcation points.
\\ ( , 70kb)
Date: Thu, 17 Jul 2008 17:28:35 GMT (2171kb,D)

Title: Paired fermionic superfluids with s- and p-wave interactions
Authors: Jesper Levinsen
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: PhD thesis
   This thesis presents theoretical work in s- and p-wave resonantly paired
Fermi gases at zero temperature. In the BEC regime of the wide-resonance s-wave
BCS-BEC crossover, the chemical potential, speed of sound, condensate
depletion, and ground state energy are computed. The quantities are calculated
in a low density approximation. The bosonic scattering length is computed
diagrammatically to be approximately 0.60a with a the fermionic scattering
length, confirming a well-known result. The perturbative approach breaks down
in the intermediate BCS-BEC crossover regime which is not investigated. Quantum
corrections are computed in the low density expansion, and the mass-imbalanced
two-species Fermi gas is investigated. For identical fermions, it is discussed
how p-wave Feshbach resonances naturally fall into two classes of "weak" and
"strong", depending on the short-distance physics. It is shown how bound
fermionic trimers appear in the strongly-resonant superfluid. The appearance of
the trimer under the strengthening of the resonance is investigated, and the
lifetime of p-wave diatomic molecules due to collisional relaxation into
trimers is estimated.
\\ ( , 2171kb)
Date: Thu, 17 Jul 2008 18:02:59 GMT (202kb)

Title: Direct observation of a localization transition in quasi-periodic
   photonic lattices
Authors: Y. Lahini, R. Pugatch, F. Pozzi, M. Sorel, R. Morandotti, N. Davidson
   and Y. Silberberg
Categories: cond-mat.dis-nn
Comments: Comments welcome
   The localization of waves in non-periodic media is a universal phenomenon,
occurring in a variety of different quantum and classical systems, including
condensed-matter, Bose-Einstein condensates in optical lattices, quantum
chaotic systems, sound waves and light. A localization phase transition is
expected to occur in three dimensional disordered systems as the strength of
disorder crosses a critical value. Recently, a crossover from an extended to a
localized phase has been observed in low-dimensional photonic lattices and
Bose-Einstein condensates. Other experiments studied the critical behaviour
near the transition in three dimensions via transmission measurements. However,
no direct observation of a localization transition for light has been reported.
In 1979 Aubry and Andre predicted that for a certain class of quasi-periodic
potentials, a localization phase transition can occur already in one-dimension.
This strongly correlated potential is markedly different from the disordered
case were the potential is uncorrelated. Here we report an experiment that
realizes the Aubry-Andre model in quasi-periodic photonic lattices. We observe
the signature of a localization phase transition by directly measuring the
expansion rates of initially narrow wave packets propagating in the lattice.
Below the transition point, all the modes of the system are extended and
therefore an initially narrow wave-packet eventually spreads across the entire
lattice. Above the critical point, all modes are localized and expansion is
suppressed. In addition, we study the effect of weak nonlinear interactions on
light propagation below and above the transition.
\\ ( , 202kb)

The replacements:

replaced with revised version Sat, 12 Jul 2008 06:37:25 GMT (698kb)

Title: Theory of correlations between ultra-cold bosons released from an
   optical lattice
Authors: E. Toth, A. M. Rey and P. B. Blakie
Categories: cond-mat.other
Comments: 18 pages, 11 figures. To appear in Phys. Rev. A. (few minor changes
   made and typos fixed)
\\ ( , 698kb)
replaced with revised version Thu, 17 Jul 2008 16:03:35 GMT (1893kb)

Title: Strongly interacting bosons in a disordered optical lattice
Authors: M. White, M. Pasienski, D. McKay, S. Zhou, D. Ceperley, B. DeMarco
Categories: physics.atom-ph cond-mat.other
Comments: 15 pages, 4 figures updated to correct errors in referencing previous
\\ ( , 1893kb)
replaced with revised version Wed, 16 Jul 2008 00:24:11 GMT (200kb)

Title: Quantum Antiferromagnetism of Fermions in Optical Lattices with
   Half-filled p-band
Authors: Kai Wu and Hui Zhai
Categories: cond-mat.str-el cond-mat.supr-con
Journal-ref: Phys. Rev. B 77, 174431 (2008)
\\ ( , 200kb)
replaced with revised version Wed, 16 Jul 2008 06:05:56 GMT (1065kb)

Title: Critical Temperature and Condensate Fraction of a Fermion Pair
Authors: Yasuhisa Inada, Munekazu Horikoshi, Shuta Nakajima, Makoto
   Kuwata-Gonokami, Masahito Ueda and Takashi Mukaiyama
Categories: cond-mat.other
\\ ( , 1065kb)
replaced with revised version Wed, 16 Jul 2008 01:34:50 GMT (92kb)

Title: Cross-Molecular Coupling in Combined Photoassociation and Feshbach
Authors: Matt Mackie, Matthew Fenty, Danielle Savage, and Jake Kesselman
Categories: physics.atom-ph physics.chem-ph
Comments: 4 pages, 2 figs, 22+ refs; v2 improved abstract, refined discussion
   of exptl motivation, improved word choice in discussion of future work; to
   appear in Phys. Rev. Lett
\\ ( , 92kb)
replaced with revised version Thu, 17 Jul 2008 01:28:02 GMT (118kb)

Title: Many-Body Effects on Nonadiabatic Feshbach Conversion in Bosonic Systems
Authors: Jie Liu, Bin Liu, and Libin Fu
Categories: cond-mat.mes-hall
Comments: 7pages 5figures
Journal-ref: Phys. Rev. A 78, 013618 (2008)
\\ ( , 118kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Thu Aug 07 2008 - 11:07:52 EST

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