Matt's arXiv selection: week ending 10 October 2008

From: Matthew Davis <>
Date: Thu, 16 Oct 2008 10:01:30 +1000

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

Hi everyone,

I'm off to the CASTU cold atom meeting in Beijing next week - I look forward to
seeing some of the subscribers to this list there, please come and say hello!

It was one of the quietest weeks I've seen for a while - this week there were 14
new preprints and 10 replacements.

Date: Fri, 3 Oct 2008 09:38:53 GMT (2437kb,D)

Title: Squeezing and entanglement in a Bose-Einstein condensate
Authors: J. Esteve, C. Gross, A. Weller, S. Giovanazzi, M.K. Oberthaler
   (Kirchhoff Institut f\"ur Physik, Heidelberg, Germany)
Categories: cond-mat.other
DOI: 10.1038/nature07332
   Entanglement, a key feature of quantum mechanics, is a resource that allows
the improvement of precision measurements beyond the conventional bound
reachable by classical means. This is known as the standard quantum limit,
already defining the accuracy of the best available sensors for various
quantities such as time or position. Many of these sensors are interferometers
in which the standard quantum limit can be overcome by feeding their two input
ports with quantum-entangled states, in particular spin squeezed states. For
atomic interferometers, Bose-Einstein condensates of ultracold atoms are
considered good candidates to provide such states involving a large number of
particles. In this letter, we demonstrate their experimental realization by
splitting a condensate in a few parts using a lattice potential. Site resolved
detection of the atoms allows the measurement of the conjugated variables atom
number difference and relative phase. The observed fluctuations imply
entanglement between the particles, a resource that would allow a precision
gain of 3.8 dB over the standard quantum limit for interferometric
\\ ( , 2437kb)
Date: Fri, 3 Oct 2008 14:10:56 GMT (28kb)

Title: Bose-Hubbard phase diagram with arbitrary filling
Authors: Niklas Teichmann, Dennis Hinrichs, Martin Holthaus, and Andre Eckardt
Categories: cond-mat.other
Comments: 4 pages, 4 figures
   We study the transition from a Mott insulator to a superfluid in both the
two- and the three-dimensional Bose-Hubbard model at zero temperature,
employing the method of the effective potential. Converting Kato's perturbation
series into an efficient numerical algorithm capable of reaching high orders,
we obtain accurate critical parameters for any filling factor. Our technique
allows us to monitor both the approach to the mean-field limit by considering
spatial dimensionalities $d > 3$, and to the quantum rotor limit of high
filling, which refers to an array of Josephson junctions.
\\ ( , 28kb)
Date: Fri, 3 Oct 2008 17:12:01 GMT (1465kb,D)

Title: Stability of a Bose-Einstein condensate revisited for composite bosons
Authors: M. Combescot and D.W. Snoke
Categories: cond-mat.other
   It is known that elementary bosons condense in a unique state, not so much
because this state has the lowest free particle energy but because it costs a
macroscopic amount of energy to put the particles into different states which
can then interact through quantum particle exchanges. Since individual
exchanges between the two fermions of a composite boson are ignored when
composite particles are replaced by elementary bosons, it is of importance to
reconsider the exchange energy argument for the stability of the Bose-Einstein
condensate in the case of composite bosons. We do this here in the light of the
new many-body theory which allows us to take exactly into account all possible
exchanges between the fermionic components of the composite bosons. We confirm
that the condensate of composite bosons is made of a unique state, this state
being moreover pure: a coherent superposition of states close in energy is
shown to be less favorable for both elementary and composite bosons.
\\ ( , 1465kb)
arXiv:0810.0400 (*cross-listing*)
Date: Thu, 2 Oct 2008 12:15:51 GMT (96kb)

Title: Strongly interacting Fermi systems in 1/N expansion: From cold atoms to
   color superconductivity
Authors: Hiroaki Abuki and Tomas Brauner
Categories: hep-ph cond-mat.supr-con nucl-th
Comments: 13 pages, REVTeX4, 11 eps figures
   We investigate the 1/N expansion proposed recently as a strategy to include
quantum fluctuation effects in the nonrelativistic, attractive Fermi gas at and
near unitarity. We extend the previous results by calculating the
next-to-leading order corrections to the critical temperature along the whole
BCS-BEC crossover. We demonstrate explicitly that the extrapolation from the
mean-field approximation, based on the $1/N$ expansion, provides a useful
approximation scheme only on the BCS side of the crossover. We then apply the
technique to the study of strongly interacting relativistic many-fermion
systems. Having in mind the application to color superconductivity in cold
dense quark matter, we develop, within a simple model, a formalism suitable to
compare the effects of order parameter fluctuations in phases with different
pairing patterns. Our main conclusion is that the relative correction to the
critical temperature is to a good accuracy proportional to the mean-field ratio
of the critical temperature and the chemical potential. As a consequence, it is
significant even rather deep in the BCS regime, where phenomenologically
interesting values of the quark-quark coupling are expected. Possible impact on
the phase diagram of color-superconducting quark matter is discussed.
\\ ( , 96kb)
Date: Sun, 5 Oct 2008 21:35:39 GMT (565kb)

Title: Spontaneous symmetry breaking in a nonlinear double-well structure
Authors: Thawatchai Mayteevarunyoo (Department of Telecommunication
   Engineering, Mahanakorn University of Technology, Bangkok, Thailand), Boris
   A. Malomed (Department of Physical Electronics, School of Electrical
   Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel),
   and Guangjiong Dong (State Key Laboratory of Precision Spectroscopy and
   Physics Department, East China Normal University, Shanghai, China)
Categories: cond-mat.other
Comments: submitted to Physical Review A
   We propose a model of a nonlinear double-well potential (NDWP), alias a
double-well pseudopotential, with the objective to study an alternative
implementation of the spontaneous symmetry breaking (SSB) in Bose-Einstein
condensates (BECs) and optical media, under the action of a potential with two
symmetric minima. In the limit case when the NDWP structure is induced by the
local nonlinearity coefficient represented by a set of two delta-functions, a
fully analytical solution is obtained for symmetric, antisymmetric and
asymmetric states. In this solvable model, the SSB bifurcation has a fully
subcritical character. Numerical analysis, based on both direct simulations and
computation of stability eigenvalues, demonstrates that, while the symmetric
states are stable up to the SSB bifurcation point, both symmetric and emerging
asymmetric states, as well as all antisymmetric ones, are unstable in the model
with the delta-functions. In the general model with a finite width of the
nonlinear-potential wells, the asymmetric states quickly become stable,
simultaneously with the switch of the SSB bifurcation from the subcritical to
supercritical type. Antisymmetric solutions may also get stabilized in the NDWP
structure of the general type, which gives rise to a bistability between them
and asymmetric states. The symmetric states require a finite norm for their
existence, an explanation to which is given. A full diagram for the existence
and stability of the trapped states in the model is produced. Experimental
observation of the predicted effects should be possible in BEC formed by
several hundred atoms.
\\ ( , 565kb)
Date: Mon, 6 Oct 2008 07:22:35 GMT (61kb)

Title: Supersolid Order of Frustrated Hard-Core Bosons in a Triangular Lattice
Authors: H. C. Jiang, M. Q. Weng, Z. Y. Weng, D. N. Sheng, and L. Balents
Categories: cond-mat.str-el
Comments: 4 pages, 4 figures
   We numerically demonstrate that a supersolid phase exists in a frustrated
hard-core boson system on a triangular lattice over a wide range of interaction
strength. In the infinite repulsion (Ising) limit, we establish a mapping to
the same problem with unfrustrated hopping, which connects the supersolid to
the known results in that case. The weak superfluidity can be destroyed or
strongly enhanced by a next nearest neighbor hopping term, which provides
valuable information for experimental realization of a supersolid phase on
optical lattice.
\\ ( , 61kb)
Date: Tue, 7 Oct 2008 22:58:53 GMT (548kb)

Title: Ultracold Heteronuclear Fermi-Fermi Molecules
Authors: A.-C. Voigt, M. Taglieber, L. Costa, T. Aoki, W. Wieser, T.W. H\"ansch
   and K. Dieckmann
Categories: cond-mat.other
Comments: 5 figures
   We report on the first creation of ultracold bosonic heteronuclear molecules
of two fermionic species, 6Li and 40K, by a magnetic field sweep across an
interspecies s-wave Feshbach resonance. This allows us to associate up to
4x10^4 molecules with high efficiencies of up to 50%. Using direct imaging of
the molecules, we measure increased lifetimes of the molecules close to
resonance of more than 100 ms in the molecule-atom mixture stored in a harmonic
\\ ( , 548kb)
Date: Wed, 8 Oct 2008 16:05:53 GMT (562kb)

Title: Induced p-wave superfluidity in two dimensions: Brane world in cold
   atoms and nonrelativistic defect CFTs
Authors: Yusuke Nishida
Categories: cond-mat.other
Comments: 22 pages, 10 figures
Report-no: INT-PUB 08-46, MIT-CTP 3984
   We propose to use a two-species Fermi gas with the interspecies s-wave
Feshbach resonance to realize p-wave superfluidity in two dimensions. By
confining one species of fermions in a two-dimensional plane immersed in the
background three-dimensional Fermi sea of the other species, an attractive
interaction is induced between two-dimensional fermions. We compute the pairing
gap in the weak-coupling regime and show that it has the symmetry of p_x+ip_y.
Because the magnitude of the pairing gap increases toward the unitarity limit,
it is possible that the critical temperature for the p_x+ip_y-wave
superfluidity becomes within experimental reach. The resulting system has a
potential application to topological quantum computation using vortices with
non-Abelian statistics. We also discuss aspects of our system in the unitarity
limit as a "nonrelativistic defect conformal field theory (CFT)". The reduced
Schr\"odinger algebra, operator-state correspondence, scaling dimensions of
composite operators, and operator product expansions are investigated.
\\ ( , 562kb)
Date: Wed, 8 Oct 2008 02:54:51 GMT (141kb)

Title: Quantum fluctuations in trapped time-dependent Bose-Einstein condensates
Authors: Michael Uhlmann
Categories: cond-mat.other
   Quantum fluctuations in time-dependent, harmonically-trapped Bose-Einstein
condensates are studied within Bogoliubov theory. An eigenmode expansion of the
linear field operators permits the diagonalization of the Bogoliubov-de Gennes
equation for a stationary condensate. When trap frequency or interaction
strength are varied, the inhomogeneity of the background gives rise to
off-diagonal coupling terms between different modes. This coupling is
negligible for low energies, i.e., in the hydrodynamic regime, and an effective
space-time metric can be introduced. The influence of the inter-mode coupling
will be demonstrated in an example, where I calculate the quasi-particle number
for a quasi-one-dimensional Bose-Einstein condensate subject to an exponential
sweep of interaction strength and trap frequency.
\\ ( , 141kb)
Date: Wed, 8 Oct 2008 23:59:03 GMT (1178kb)

Title: Noise Correlations in low-dimensional systems of ultracold atoms
Authors: L. Mathey, A. Vishwanath, and E. Altman
Categories: cond-mat.other
Comments: 14 pages, 7 figures
   We derive relations between standard order parameter correlations and the
noise correlations in time of flight images, which are valid for systems with
long range order as well as low dimensional systems with algebraic decay of
correlations. Both Bosonic and Fermionic systems are considered. For one
dimensional Fermi systems we show that the noise correlations are equally
sensitive to spin, charge and pairing correlations and may be used to
distinguish between fluctuations in the different channels. This is in contrast
to linear response experiments, such as Bragg spectroscopy, which are only
sensitive to fluctuations in the particle-hole channel (spin or charge). For
Bosonic systems we find a sharp peak in the noise correlation at opposite
momenta that signals pairing correlations in the depletion cloud. In a
condensate with true long range order, this peak is a delta function and we can
use Bogoliubov theory to study its temperature dependence. Interestingly we
find that it is enhanced with temperature in the low temperature limit. In one
dimensional condensates with only quasi-long range (i.e. power-law) order the
peak in the noise correlations also broadens to a power-law singularity.
\\ ( , 1178kb)
Date: Thu, 9 Oct 2008 07:54:04 GMT (401kb)

Title: Nonlinear Ramsey interferometry with the Rosen-Zener pulses on a
   two-component Bose-Einstein condensate
Authors: Sheng-Chang Li, Li-Bin Fu, Wen-Shan Duan, Jie Liu
Categories: cond-mat.other
Comments: 8 pages, 9 figures
   We propose a feasible scheme to realize nonlinear Ramsey interferometry with
a two-component Bose-Einstein condensate, where the nonlinearity arises from
the interaction between coherent atoms. In our scheme, two Rosen-Zener pulses
are separated by an intermediate holding period of variable duration and
through varying the holding period we have observed nice Ramsey interference
patterns in time domain. In contrast to the standard Ramsey fringes our
nonlinear Ramsey patterns display diversiform structures ascribed to the
interplay of the nonlinearity and asymmetry. In particular, we find that the
frequency of the nonlinear Ramsey fringes exactly reflects the strength of
nonlinearity as well as the asymmetry of system. Our finding suggests a
potential application of the nonlinear Ramsey interferometry in calibrating the
atomic parameters such as scattering length and energy spectrum.
\\ ( , 401kb)
Date: Thu, 9 Oct 2008 14:45:40 GMT (1454kb)

Title: Dipole oscillations of confined lattice bosons in one dimension
Authors: Simone Montangero, Rosario Fazio, Peter Zoller, Guido Pupillo
Categories: cond-mat.other
Comments: 4 pages, 3 figures
   We study the dynamics of a non-integrable system comprising interacting cold
bosons trapped in an optical lattice in one-dimension by means of exact
time-dependent numerical DMRG techniques. Particles are confined by a parabolic
potential, and dipole oscillations are induced by displacing the trap center of
a few lattice sites. Depending on the system parameters this motion can vary
from undamped to overdamped. We study the dipole oscillations as a function of
the lattice displacement, the particle density and the strength of
interparticle interactions. These results explain the recent experiment C.D.
Fertig et al., Phys. Rev. Lett. 94, 120403 (2005).
\\ ( , 1454kb)
Date: Thu, 9 Oct 2008 17:47:36 GMT (76kb)

Title: DC and AC Josephson effects with superfluid Fermi atoms across a
   Feshbach resonance
Authors: L. Salasnich, F. Ancilotto, N. Manini, and F. Toigo
Categories: cond-mat.other cond-mat.supr-con
Comments: 8 pages, 4 figures, presented at the Scientific Seminar on Physics of
   Cold Trapped Atoms, 17th International Laser Physics Workshop (Trondheim,
   June 30 - July 4, 2008)
   We show that both DC and AC Josephson effects with superfluid Fermi atoms in
the BCS-BEC crossover can be described at zero temperature by a nonlinear
Schrodinger equation (NLSE). By comparing our NLSE with mean-field extended BCS
calculations, we find that the NLSE is reliable in the BEC side of the
crossover up to the unitarity limit. The NLSE can be used for weakly-linked
atomic superfluids also in the BCS side of the crossover by taking the
tunneling energy as a phenomenological parameter.
\\ ( , 76kb)
Date: Thu, 9 Oct 2008 18:59:30 GMT (68kb)

Title: Momentum-space interferometry with trapped ultracold atoms
Authors: A. Ruschhaupt, A. del Campo, J. G. Muga
Categories: quant-ph
Comments: 8 pages
   Quantum interferometers are generally set so that phase differences between
paths in coordinate space combine constructive or destructively. Indeed, the
interfering paths can also meet in momentum space leading to momentum-space
fringes. We propose and analyze a method to produce interference in momentum
space by phase-imprinting part of a trapped atomic cloud with a detuned laser.
For one-particle wave functions analytical expressions are found for the fringe
width and shift versus the phase imprinted. The effects of unsharpness or
displacement of the phase jump are also studied, as well as many-body effects
to determine the potential applicability of momentum-space interferometry.
\\ ( , 68kb)

The replacements:

replaced with revised version Thu, 2 Oct 2008 21:25:37 GMT (25kb)

Title: Adiabatic nonlinear probes of one-dimensional Bose gases
Authors: C. De Grandi, R. A. Barankov, A. Polkovnikov
Categories: cond-mat.other
Comments: 4+ pages, 4 figures, revised version
\\ ( , 25kb)
replaced with revised version Fri, 3 Oct 2008 09:10:10 GMT (0kb,I)

Title: Bose-Einstein condensation in an optical lattice: A perturbation
Authors: C. Trallero-Giner, V. Lopez-Richard, Ming-Chiang Chung, Andreas
Categories: cond-mat.other
Comments: the paper has been withdrawn
\\ ( , 0kb)
replaced with revised version Sun, 5 Oct 2008 19:42:05 GMT (215kb)

Title: Phase separation and collapse in Bose-Fermi mixtures with a Feshbach
Authors: F. M. Marchetti, C. Mathy, M. M. Parish, D. A. Huse
Categories: cond-mat.other
Comments: 7 pages, 3 figures. Extended version
\\ ( , 215kb)
replaced with revised version Sat, 4 Oct 2008 15:26:37 GMT (2757kb)

Title: Long-range correlations of density in a Bose-Einstein condensate
   expanding in a random potential
Authors: N. Cherroret, S.E. Skipetrov
Categories: cond-mat.dis-nn cond-mat.mes-hall
Comments: 4 pages, 5 figures
\\ ( , 2757kb)
replaced with revised version Mon, 6 Oct 2008 14:11:35 GMT (398kb,D)

Title: Scattering and binding of different atomic species in a one-dimensional
   optical lattice
Authors: R. T. Piil, N. Nygaard, and K. Molmer
Categories: cond-mat.other
Comments: 5 pages, 4 figures
Journal-ref: Phys. Rev. A 78, 033611 (2008)
\\ ( , 398kb)
replaced with revised version Tue, 7 Oct 2008 12:57:26 GMT (24kb)

Title: Microscopic diagonal entropy and its connection to basic thermodynamic
Authors: Roman Barankov and Anatoli Polkovnikov
Categories: cond-mat.stat-mech hep-th quant-ph
Comments: minor revisions, 4. pages 2 figures. Added numerical example and
   discussion of ergodicity
\\ ( , 24kb)
replaced with revised version Tue, 7 Oct 2008 01:15:12 GMT (732kb,D)

Title: Heteronuclear quantum gas mixtures
Authors: C. Ospelkaus, S. Ospelkaus
Categories: cond-mat.other cond-mat.stat-mech physics.atom-ph
Comments: 72 pages, updated to published version
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 41, 203001 (2008)
DOI: 10.1088/0953-4075/41/20/203001
\\ ( , 732kb)
replaced with revised version Wed, 8 Oct 2008 15:44:06 GMT (50kb)

Title: Efimov states near a Feshbach resonance
Authors: P. Massignan and H. T. C. Stoof
Categories: cond-mat.other
Comments: Version accepted for publication: minor revisions concerning the
   comparison with the cesium experiment
Journal-ref: Phys. Rev. A 78, 030701(R) (2008)
DOI: 10.1103/PhysRevA.78.030701
\\ ( , 50kb)
replaced with revised version Thu, 9 Oct 2008 16:11:46 GMT (40kb)

Title: Realizing the strongly correlated $d$-Mott state in a fermionic cold
   atom optical lattice
Authors: Michael R. Peterson, Chuanwei Zhang, Sumanta Tewari, S. Das Sarma
Categories: cond-mat.str-el quant-ph
Comments: 4 pages, 5 figures
Journal-ref: Phys. Rev. Lett. 101, 150406 (2008) v2 is final version
\\ ( , 40kb)
replaced with revised version Thu, 9 Oct 2008 08:14:25 GMT (535kb,D)

Title: Engineering the quantum transport of atomic wavefunctions over
   macroscopic distances
Authors: A. Alberti, V. V. Ivanov, G. M. Tino and G. Ferrari
Categories: quant-ph
Comments: 5 pages, 5 figures
\\ ( , 535kb)

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 Wed Oct 29 2008 - 09:15:09 EST

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