Matt's arXiv selection: week ending 31 August 2007.

From: Matthew Davis <>
Date: Fri, 14 Sep 2007 15:05:15 +1000 (EST)

This week there were 18 new preprints and 6 replacements.

Date: Fri, 24 Aug 2007 13:44:06 GMT (283kb,D)

Title: Supersolid Bose-Fermi Mixtures in Optical Lattices
Authors: I. Titvinidze, M. Snoek, W. Hofstetter
Categories: cond-mat.other
Comments: 4 pages, 5 pictures
   We study a mixture of strongly interacting bosons and spinless fermions with
on-site repulsion in a three-dimensional optical lattice. In order to
investigate the regime of strong interactions, we develop and apply a
generalized DMFT (gDMFT) scheme, which consists of dynamical mean-field theory
(DMFT) for the fermions, combined with static Gutzwiller mean-field theory for
the bosons. We restrict ourselves to the case of half filling, where we find a
rich phase diagram. For weak Bose-Fermi repulsion a supersolid forms, in which
the bosons are superfluid and both fermions and bosons have a spatially
modulated density, i.e. charge-density wave order. For stronger interspecies
repulsion the bosons become localized while the charge density wave order
persists. The system is unstable against phase separation for weak repulsion
among the bosons.
\\ ( , 283kb)
Date: Fri, 24 Aug 2007 19:55:21 GMT (95kb)

Title: Time-dependent density-functional theory, Hubbard model, and exact
   results for 1D contact-interacting fermions in a double well potential
Authors: R. J. Magyar
Categories: cond-mat.other cond-mat.mtrl-sci
   Two of the most popular quantum mechanical models of interacting fermions are
compared to each other and to potentially exact solutions for a pair of
contact-interacting fermions trapped in a 1D double-well potential, a model of
atoms in an optical lattice or electrons of a Hydrogen molecule in a strong
magnetic field. An exact few-body Hamiltonian is solved numerically in momentum
space yielding a highly-correlated eigenspectrum. Additionally, approximate
ground-state energies are obtained using both density functional theory (DFT)
with the exact-exchange / local correlation (EXX/LDA) functional and 2-site
Hubbard models. A 1D adiabatic LDA kernel is constructed for use in
time-dependent density functional theory (TDDFT), and the resulting
excited-state spectrum is compared to the exact and Hubbard results. TDDFT is
shown to provide exceptionally accurate results in the double-well range with
non-adiabatic effects accounting for deviations for stronger interactions. As
expected, the Hubbard model outperforms DFT at large separations but breaks
down at intermediate spacings due to improper scaling. A newly introduced
functional based on the effective local fermion number provides accurate
results for large spacings.
\\ ( , 95kb)
Date: Fri, 24 Aug 2007 09:16:11 GMT (230kb)

Title: Recent progress on the manipulation of single atoms in optical tweezers
   for quantum computing
Authors: A. Browaeys, J. Beugnon, C. Tuchendler, H. Marion, A. Ga\"etan, Y.
   Miroshnychenko, B. Darqui\'e, J. Dingjan, Y. R. P. Sortais, A. M. Lance, M.
   P. A. Jones, G. Messin, P. Grangier
Categories: quant-ph
Comments: Proceedings of the ICOLS07 conference
   This paper summarizes our recent progress towards using single rubidium atoms
trapped in an optical tweezer to encode quantum information. We demonstrate
single qubit rotations on this system and measure the coherence of the qubit.
We move the quantum bit over distances of tens of microns and show that the
coherence is reserved. We also transfer a qubit atom between two tweezers and
show no loss of coherence. Finally, we describe our progress towards
conditional entanglement of two atoms by photon emission and two-photon
\\ ( , 230kb)
Date: Fri, 24 Aug 2007 19:25:31 GMT (11kb)

Title: Collapse times for attractive Bose-Einstein condensates
Authors: Esteban Calzetta
Categories: cond-mat.other
Comments: 12 pages
   We argue that the main mechanism for condensate collapse in an attractive
Bose-Einstein condensate is the loss of coherence between atoms a finite
distance apart, rather than the growth of the occupation number in
noncondensate modes. Since the former mechanism is faster than the latter by a
factor of approximately 3/2, this helps to dispell the apparent failure of
field theoretical models in predicting the collapse time of the condensate.
\\ ( , 11kb)
Date: Fri, 24 Aug 2007 11:30:36 GMT (232kb)

Title: Destruction of Anderson localization by a weak nonlinearity
Authors: A. S. Pikovsky and D. L. Shepelyansky
Categories: cond-mat.dis-nn
Comments: 4 pages, 5 figs
   We study numerically a spreading of an initially localized wave packet in a
one-dimensional discrete nonlinear Schr\"odinger lattice with disorder. We
demonstrate that above a certain critical strength of nonlinearity the Anderson
localization is destroyed and an unlimited subdiffusive spreading of the field
along the lattice occurs. The second moment grows with time $ \propto
t^\alpha$, with the exponent $\alpha$ being in the range $0.3 - 0.4$. For small
nonlinearities the distribution remains localized in a way similar to the
linear case.
\\ ( , 232kb)
Date: Fri, 24 Aug 2007 12:14:58 GMT (71kb)

Title: Optical polarizabilities of large molecules measured in near-field
Authors: Lucia Hackermueller, Klaus Hornberger, Stefan Gerlich, Michael Gring,
   Hendrik Ulbricht, Markus Arndt
Categories: quant-ph
Comments: 5 pages, 3 Figures
   We discuss a novel application of matter wave interferometry to characterize
the scalar optical polarizability of molecules at 532 nm. The interferometer
presented here consists of two material absorptive gratings and one central
optical phase grating. The interaction of the molecules with the standing light
wave is determined by the optical dipole force and is therefore directly
dependent on the molecular polarizability at the wavelength of the diffracting
laser light. By comparing the observed matter-wave interference contrast with a
theoretical model for several intensities of the standing light wave and
molecular velocities we can infer the polarizability in this first
proof-of-principle experiment for the fullerenes C60 and C70 and we find a good
agreement with literature values.
\\ ( , 71kb)
Date: Mon, 27 Aug 2007 08:42:01 GMT (111kb)

Title: One-dimensional fermionic gases with attractive p-wave interaction in a
   hard-wall trap
Authors: Yajiang Hao, Yunbo Zhang, Shu Chen
Categories: cond-mat.other cond-mat.str-el
Comments: 6 pages, 5 figures
   We investigate the ground state of the one-dimensional fermionic system
enclosed in a hard-wall trap with attractive contact p-wave interactions. Based
on the Bethe ansatz method, the explicit wave function is derived by
numerically solving the Bethe ansatz equations for the full physical regimes
($-\infty \leq c_F\leq 0$). With the exact wave function some quantities which
are important in many-body physics are obtained, including the one-body density
matrix and the momentum distribution of the ground state for finite system. It
is shown that the shell structure of the density profiles disappears with the
increase of the interaction and in the fermionic Tonks-Girardeau (FTG) limit
the density distribution shows the same behavior as that of an ideal Bose gas.
However the one-body density matrix and the momentum distribution exhibit
completely different structures compared with their bosonic counterparts.
\\ ( , 111kb)
Date: Mon, 27 Aug 2007 16:07:53 GMT (66kb)

Title: Spin dynamics in a one-dimensional ferromagnetic Bose gas
Authors: M. B. Zvonarev, V. V. Cheianov, T. Giamarchi
Categories: cond-mat.other
   We investigate the propagation of spin excitations in a one-dimensional (1D)
ferromagnetic Bose gas. While the spectrum of longitudinal spin waves in this
system is sound-like, the dispersion of transverse spin excitations is
quadratic making a direct application of the Luttinger Liquid (LL) theory
impossible. By using a combination of different analytic methods we derive the
large time asymptotic behavior of the spin-spin dynamical correlation function
for strong interparticle repulsion. The result has an unusual structure
associated with a crossover from the regime of trapped spin wave to an open
regime and does not have analogues in known low-energy universality classes of
quantum 1D systems.
\\ ( , 66kb)
Date: Mon, 27 Aug 2007 17:12:41 GMT (81kb)

Title: Complex solitons with power law behaviour in Bose-Einstein condensates
   near Feshbach resonance
Authors: Utpal Roy, Rajneesh Atre, C. Sudheesh, C. Nagaraja Kumar, Prasanta K.
Categories: cond-mat.other
Comments: 4 pages, 2 figures
   Complex, localized stable solitons, characterized by a power law behaviour,
are found for a quasi-one-dimensional Bose-Einstein condensate near Feshbach
resonance. Both dark and bright solitons can be excited in the experimentally
allowed parameter domain, when two and three-body interactions are respectively
repulsive and attractive. These solutions are obtained for non-zero chemical
potential, unlike their unstable real counterparts which exist in the limit of
vanishing $\mu$. The dark solitons travel with constant speed, which is quite
different from the Lieb mode, where profiles with different speeds, bounded
above by sound velocity can exist for specified interaction strengths.
\\ ( , 81kb)
Date: Mon, 27 Aug 2007 17:53:27 GMT (914kb)

Title: Hyperfine spectra of trapped Bosons in optical lattices
Authors: Kaden R.A. Hazzard and Erich J. Mueller
Categories: cond-mat.other
Comments: 7 pages, 5 figures, revtex4
   We calculate the interaction induced inhomogeneous broadening of spectral
lines in a trapped Bose gas as a function of the depth of a three-dimensional
cubic optical lattice. As observed in recent experiments, we find that the
terraced "wedding-cake" structure of Mott plateaus splits the spectrum into a
series of discrete peaks. The spectra are extremely sensitive to density
corrugations and trap anharmonicities. For example, even when the majority of
the cloud is superfluid the spectrum displays discrete peaks.
\\ ( , 914kb)
Date: Sun, 26 Aug 2007 09:50:32 GMT (69kb)

Title: Nonlinear control of chaotic walking of atoms in an optical lattice
Authors: Argonov V. Yu, S. V. Prants
Categories: quant-ph
Comments: 6 pages, 4 figures
   Centre-of-mass atomic motion in an optical lattice near the resonance is
shown to be a chaotic walking due to the interplay between coherent internal
atomic dynamics and spontaneous emission. Statistical properties of chaotic
atomic motion can be controlled by the single parameter, the detuning between
the atomic transition frequency and the laser frequency. We derive a
Fokker-Planck equation in the energetic space to describe the atomic transport
near the resonance and demonstrate numerically how to manipulate the atomic
motion varying the detuning.
\\ ( , 69kb)
Date: Tue, 28 Aug 2007 00:38:12 GMT (402kb)

Title: Classical analogs for Rabi-oscillations, Ramsey-fringes, and spin-echo
   in Josephson junctions
Authors: Jeffrey E. Marchese, Matteo Cirillo and Niels Gronbech-Jensen
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 16 pages, 7 figures
   We investigate the results of recently published experiments on the quantum
behavior of Josephson circuits in terms of the classical modelling based on the
resistively and capacitively-shunted (RCSJ) junction model. Our analysis shows
evidence for a close analogy between the nonlinear behavior of a pulsed
microwave-driven Josephson junction at low temperature and low dissipation and
the experimental observations reported for the Josephson circuits.
Specifically, we demonstrate that Rabi-oscillations, Ramsey-fringes, and
spin-echo observations are not phenomena with a unique quantum interpretation.
In fact, they are natural consequences of transients to phase-locking in
classical nonlinear dynamics and can be observed in a purely classical model of
a Josephson junction when the experimental recipe for the application of
microwaves is followed and the experimental detection scheme followed. We
therefore conclude that classical nonlinear dynamics can contribute to the
understanding of relevant experimental observations of Josephson response to
various microwave perturbations at very low temperature and low dissipation.
\\ ( , 402kb)
Date: Tue, 28 Aug 2007 10:36:49 GMT (34kb)

Title: Entanglement and correlation functions following a local quench: a
   conformal field theory approach
Authors: Pasquale Calabrese and John Cardy
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 19 pages, 4 figures
   We show that the dynamics resulting from preparing a one-dimensional quantum
system in the ground state of two decoupled parts, then joined together and
left to evolve unitarily with a translational invariant Hamiltonian (a local
quench), can be described by means of quantum field theory. In the case when
the corresponding theory is conformal, we study the evolution of the
entanglement entropy for different bi-partitions of the line. We also consider
the behavior of one- and two-point correlation functions. All our findings may
be explained in terms of a picture, that we believe to be valid more generally,
whereby quasiparticles emitted from the joining point at the initial time
propagate semiclassically through the system.
\\ ( , 34kb)
Date: Tue, 28 Aug 2007 19:33:16 GMT (541kb)

Title: Formal analytical solutions for the Gross-Pitaevskii equation
Authors: C. Trallero-Giner, Julio C. Drake-Perez, V. Lopez-Richard, Joseph L.
Categories: cond-mat.other
Comments: 8 figures
   Considering the Gross-Pitaevskii integral equation we are able to formally
obtain an analytical solution for the order parameter $\Phi (x)$ and for the
chemical potential $\mu $ as a function of a unique dimensionless non-linear
parameter $\Lambda $. We report solutions for different range of values for the
repulsive and the attractive non-linear interactions in the condensate. Also,
we study a bright soliton-like variational solution for the order parameter for
positive and negative values of $\Lambda $. Introducing an accumulated error
function we have performed a quantitative analysis with other well-established
methods as: the perturbation theory, the Thomas-Fermi approximation, and the
numerical solution. This study gives a very useful result establishing the
universal range of the $\Lambda $-values where each solution can be easily
implemented. In particular we showed that for $\Lambda <-9$, the bright soliton
function reproduces the exact solution of GPE wave function.
\\ ( , 541kb)
Date: Tue, 28 Aug 2007 18:10:09 GMT (48kb)

Title: Trapping radioactive ^{82}Rb in an optical dipole trap and evidence of
   spontaneous spin polarization
Authors: D. Feldbaum, H. Wang, J. Weinstein, D. Vieira and X. Zhao
Categories: quant-ph
Comments: 4 pages, 4 figures
   Optical trapping of selected species of radioactive atoms has great potential
in precision measurements for testing fundamental physics such as EDM, PNC and
parity violating beta-decay asymmetry correlation coefficients. We report
trapping of 10^4 radioactive ^{82}Rb atoms (t_{1/2}=75 s) with a trap lifetime
of ~55 seconds in an optical dipole trap. Transfer efficiency from the
magneto-optical trap was ~14%. We further report the evidence of spontaneous
spin polarization of the atoms in optical dipole trap loading. This advancement
is an important step towards a new generation of precision J-beta correlations
measurements with polarized ^{82}Rb atoms.
\\ ( , 48kb)
Date: Wed, 29 Aug 2007 13:59:41 GMT (273kb)

Title: Cruising through molecular bound state manifolds with radio frequency
Authors: F. Lang, P.v.d. Straten, B. Brandst\"atter, G. Thalhammer, K. Winkler,
   P.S. Julienne, R. Grimm and J. Hecker Denschlag
Categories: quant-ph
Comments: 5 pages, 5 figures, submitted for publication
   The emerging field of ultracold molecules with their rich internal structure
is currently attracting a lot of interest. Various methods have been developed
to produce ultracold molecules in pre-set quantum states. For future
experiments it will be important to efficiently transfer these molecules from
their initial quantum state to other quantum states of interest. Optical Raman
schemes are excellent tools for transfer, but can be involved in terms of
equipment, laser stabilization and finding the right transitions. Here we
demonstrate a very general and simple way for transfer of molecules from one
quantum state to a neighboring quantum state with better than 99% efficiency.
The scheme is based on Zeeman tuning the molecular state to avoided level
crossings where radio-frequency transitions can then be carried out. By
repeating this process at different crossings, molecules can be successively
transported through a large manifold of quantum states. As an important
spin-off of our experiments, we demonstrate a high-precision spectroscopy
method for investigating level crossings.
\\ ( , 273kb)
Date: Thu, 30 Aug 2007 18:30:51 GMT (33kb)

Title: Shell Effects in the First Sound Velocity of an Ultracold Fermi Gas
Authors: Luca Salasnich and Flavio Toigo
Categories: cond-mat.stat-mech cond-mat.other
Comments: 6 pages, 1 figure, submitted for the Proceedings of the International
   Symposium on Quantum Fluids and Solids 2007, Kazan
   We investigate the first sound of a normal dilute and ultracold two-component
Fermi gas in a harmonic microtube, i.e. a cylinder with harmonic transverse
radial confinement in the length-scale of microns. We show that the velocity of
the sound that propagates along the axial direction strongly depends on the
dimensionality of the system. In particular, we predict that the first-sound
velocity display shell effects: by increasing the density, that is by inducing
the crossover from one-dimension to three-dimensions, the first-sound velocity
shows jumps in correspondence with the filling of harmonic modes. The
experimental achievability of these effects is discussed by considering 40K
\\ ( , 33kb)
Date: Thu, 30 Aug 2007 16:28:24 GMT (489kb)

Title: Optimal transport of ultracold atoms in the non-adiabatic regime
Authors: A. Couvert (LKB - Lhomond), T. Kawalec (LKB - Lhomond), G. Reinaudi
   (LKB - Lhomond), David Guery-Odelin (LKB - Lhomond)
Categories: cond-mat.other
Proxy: ccsd hal-00168928
   We report on the transport of ultracold atoms with optical tweezers in the
non-adiabatic regime i.e. on a time scale on the order of the oscillation
period. To quantitatively interpret our data, we provide a fruitful analogy
between the transport and the Fraunhofer diffraction of an object having a
transmittance with the same shape as the one of the velocity profile imposed on
center of the trap. The damping of the Kohn's mode due to the non-linear mixing
turns out to be reminiscent of the effect of a finite coherence source for its
optical counterpart.
\\ ( , 489kb)

The replacments:

replaced with revised version Fri, 24 Aug 2007 21:30:51 GMT (22kb)

Title: Bose-Einstein condensate in a harmonic trap decorated with Dirac delta
Authors: Haydar Uncu, Devrim Tarhan, Ersan Demiralp, Ozgur E. Mustecaplioglu
Categories: cond-mat.other quant-ph
Comments: 8 pages, 8 figures
Journal-ref: PHYSICAL REVIEW A 76, 013618 (2007)
\\ ( , 22kb)
replaced with revised version Sun, 26 Aug 2007 10:00:11 GMT (117kb)

Title: Coherent state path integral and super-symmetry for condensates composed
   of bosonic and fermionic atoms
Authors: Bernhard Mieck
Categories: cond-mat.stat-mech
Journal-ref: Fortschr. Phys. ("Progress of Physics") Vol. 55, (No. 9-10), pp.
   989-1120 (2007)
\\ ( , 117kb)
replaced with revised version Tue, 28 Aug 2007 14:13:09 GMT (33kb)

Title: Thermodynamical Properties of a Rotating Ideal Bose Gas
Authors: Sebastian Kling, Axel Pelster
Categories: cond-mat.stat-mech
Comments: Author Information under
Journal-ref: Phys. Rev. A 76, 023609 (2007)
\\ ( , 33kb)
replaced with revised version Wed, 29 Aug 2007 17:45:47 GMT (267kb)

Title: Criterion for bosonic superfluidity in an optical lattice
Authors: Roberto B. Diener, Qi Zhou, Hui Zhai, and Tin-Lun Ho
Categories: cond-mat.other
Comments: 4 pages, 2 figures; published version
Journal-ref: Physical Review Letters, 98, 180404 (2007)
\\ ( , 267kb)
replaced with revised version Wed, 29 Aug 2007 03:50:02 GMT (34kb)

Title: Formation of sonic horizon in isotropically expanding Bose-Einstein
Authors: Yasunari Kurita, Takao Morinari
Categories: cond-mat.other gr-qc hep-th
Comments: 7 pages, 8 figures, section 3 extended, figures and references added
Report-no: YITP-07-16, OCU-PHYS-264, AP-GR-40
\\ ( , 34kb)
arXiv:0704.2280 (*cross-listing*)
replaced with revised version Thu, 30 Aug 2007 07:40:41 GMT (201kb)

Title: Full-time dynamics of modulational instability in spinor Bose-Einstein
Authors: Evgeny V. Doktorov, Vassilis M. Rothos and Yuri S. Kivshar
Categories: nlin.SI cond-mat.other
Comments: 6 pages, 2 figures, text slightly extended, a reference added
Journal-ref: Physical Review A 76, 013626 (2007)
\\ ( , 201kb)

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 Fri Sep 14 2007 - 15:05:15 EST

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