CATCH UP: Matt's arXiv selection, Monday 14th August 2006.

From: Matthew Davis <>
Date: Tue, 15 Aug 2006 02:11:30 +1000 (EST)

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

Hi everyone,

Well it turned out that I did take two weeks holiday, and hence this is a catch
up arXiv email: it is a summary of 11 days worth of mailings.

The abstracts:

Paper: physics/0607248
Date: Thu, 27 Jul 2006 09:34:00 GMT (133kb)

Title: Photodetachment of cold OH- in a multipole ion trap
Authors: S. Trippel, J. Mikosch, R. Berhane, R. Otto, M. Weidemuller, and R.
Subj-class: Atomic Physics
   The absolute photodetachment cross section of OH- anions at a rotational and
translational temperature of 170K is determined by measuring the
detachment-induced decay rate of the anions in a multipole radio-frequency ion
trap. In comparison with previous results, the obtained cross section shows the
importance of the initial rotational state distribution. Using a tomography
scan of the photodetachment laser through the trapped ion cloud, the derived
cross section is model-independent and thus features a small systematic
uncertainty. The tomography also yields the column density of the OH- anions in
the 22-pole ion trap in good agreement with the expected trapping potential of
a large field free region bound by steep potential walls.
\\ ( , 133kb)
Paper: physics/0607254
Date: Thu, 27 Jul 2006 14:09:37 GMT (84kb)

Title: Strong relative intensity squeezing by 4-wave mixing in Rb vapor
Authors: C. F. McCormick, V. Boyer, E. Arimondo, P. D. Lett
Comments: Submitted to Optics Letters
Subj-class: Optics; Atomic Physics
   We have measured -3.5 dB (-8.1 dB corrected for losses) relative intensity
squeezing between the probe and conjugate beams generated by stimulated,
nondegenerate four-wave mixing in hot rubidium vapor. Unlike early observations
of squeezing in atomic vapors based on saturation of a two-level system, our
scheme uses a resonant nonlinearity based on ground-state coherences in a
three-level system. Since this scheme produces narrowband, squeezed light near
an atomic resonance it is of interest for experiments involving cold atoms or
atomic ensembles.
\\ ( , 84kb)
Paper: physics/0512015
replaced with revised version Thu, 27 Jul 2006 07:23:27 GMT (169kb)

Title: A ring trap for ultracold atoms
Authors: Olivier Morizot (LPL), Yves Colombe (LPL), Vincent Lorent (LPL),
   H\'{e}l\`{e}ne Perrin (LPL), Barry M. Garraway (DPA, UNIVERSITY OF SUSSEX)
Comments: 4 figures, 10 pages ; the order of the sections has been changed ; to
   appear in Phys. Rev. A
Proxy: ccsd ccsd-00015124
Subj-class: Atomic Physics
\\ ( , 169kb)
Paper: cond-mat/0607775
Date: Fri, 28 Jul 2006 19:50:46 GMT (375kb)

Title: Superfluid transition in a rotating resonantly-interacting Fermi gas
Authors: Martin Y. Veillette, Daniel E. Sheehy, Leo Radzihovsky and Victor
   Gurarie (University Of Colorado)
Comments: 4 pages, 3 figures
Subj-class: Superconductivity
   We study a rotating atomic Fermi gas near a narrow s-wave Feshbach resonance
in a uniaxial harmonic trap with frequencies $\Omega_\perp$, $\Omega_z$. Our
primary prediction is the upper-critical angular velocity, $\omega_{c2}
(\delta,T)$, as a function of temperature $T$ and resonance detuning $\delta$,
ranging across the BEC-BCS crossover. The rotation-driven suppression of
superfluidity at $\omega_{c2}$ is quite distinct in the BCS and BEC regimes,
with the former controlled by Cooper-pair depairing and the latter by the
dilution of bosonic molecules. At low $T$ and $\Omega_z\ll\Omega_\perp$, in the
BCS and crossover regimes of $0 \lesssim \delta \lesssim \delta_c$,
$\omega_{c2}$ is implicitly given by $\hbar \sqrt{\omega_{c2}^2
+\Omega_\perp^2}\approx 2\Delta \sqrt{\hbar \Omega_\perp/\epsilon_F}$,
vanishing as $\omega_{c2} \sim\Omega_\perp(1-\delta/\delta_c)^{1/2}$ near
$\delta_c\approx 2\epsilon_{F} + \frac\gamma 2\epsilon_{F}
\ln(\epsilon_F/\hbar\Omega_\perp)$ (with $\Delta$ the BCS gap and $\gamma$
resonance width), and extending bulk result $\hbar\omega_{c2} \approx
2\Delta^2/\epsilon_{F}$ to a finite number of atoms in a trap. In the BEC
regime of $\delta < 0$ we find $\omega_{c2} \to\Omega^-_\perp$, where molecular
superfluidity can only be destroyed by large quantum fluctuations associated
with comparable boson and vortex densities.
\\ ( , 375kb)
Paper: cond-mat/0607776
Date: Fri, 28 Jul 2006 19:53:26 GMT (72kb)

Title: The potential energy of a $^{40}$K Fermi gas in the BCS-BEC crossover
Authors: J. T. Stewart, J. P. Gaebler, C. A. Regal, and D. S. Jin
Subj-class: Other
   We present a measurement of the potential energy of an ultracold trapped gas
of $^{40}$K atoms in the BCS-BEC crossover and investigate the temperature
dependence of this energy at unitarity. In particular we study the ratio of the
potential energy of the gas at unitarity to that of a non-interacting gas, and
in the T=0 limit we extract the universal many-body parameter $\beta$. We find
$\beta = -0.54^{+0.05}_{-0.12}$; this value is consistent with previous
measurements using $^{6}$Li atoms and also with recent theory and Monte Carlo
calculations. This result demonstrates the universality of ultracold Fermi
gases in the strongly interacting regime.
\\ ( , 72kb)
Paper: cond-mat/0603574
replaced with revised version Fri, 28 Jul 2006 02:12:55 GMT (273kb)

Title: Asymmetric double-well potential for single atom interferometry
Authors: A. I. Sidorov, B. J. Dalton, S. M. Whitlock, and F. Scharnberg
Comments: 9 pages, 6 figures
Subj-class: Other
\\ ( , 273kb)
Paper: cond-mat/0603859
replaced with revised version Fri, 28 Jul 2006 10:33:55 GMT (67kb)

Title: Ground state cooling of atoms in optical lattices
Authors: M. Popp, J. J. Garcia-Ripoll, K. G. H. Vollbrecht, J. I. Cirac
Comments: 12 pages, 7 figures
Subj-class: Statistical Mechanics
\\ ( , 67kb)
Paper: quant-ph/0607200
Date: Fri, 28 Jul 2006 07:49:07 GMT (159kb)

Title: New uncertainty relations for tomographic entropy: Application to
   squeezed states and solitons
Authors: Sergio De Nicola, Renato Fedele, Margarita A. Man'ko, Vladimir I.
Comments: 18 pages, 2 figures, to be published in European Physical Journal B
   Using the tomographic probability distribution (symplectic tomogram)
describing the quantum state (instead of the wave function or density matrix)
and properties of recently introduced tomographic entropy associated with the
probability distribution, the new uncertainty relation for the tomographic
entropy is obtained. Examples of the entropic uncertainty relation for squeezed
states and solitons of the Bose--Einstein condensate are considered.
\\ ( , 159kb)
Paper: quant-ph/0607201
Date: Fri, 28 Jul 2006 08:55:06 GMT (5kb)

Title: Second Quantization and Bogoliubov Approximation
Authors: Bayram Kurucay
   Recent experiments with trapped alkali atoms have drawn enormous interest to
the theoretical studies concerning Bose-Einstein condensation. The purpose of
this paper is to review one of the approaches to study bosonic matter at zero
temperature, namely the Bogoliubov approximation. Review of a necessary tool,
the second quantization, will also be made.
\\ ( , 5kb)
Paper: cond-mat/0607781
Date: Fri, 28 Jul 2006 22:31:20 GMT (796kb)

Title: Quantized Vortex States of Strongly Interacting Bosons in a Rotating
   Optical Lattice
Authors: Rajiv Bhat, B.M.Peden, B.T.Seaman, M.Kramer, L.D.Carr and M.J.Holland
Comments: 12 Pages, 13 Figures, Version 1
Subj-class: Statistical Mechanics
   Bose gases in rotating optical lattices combine two important topics in
quantum physics: superfluid rotation and strong correlations. In this paper, we
examine square two-dimensional systems at zero temperature comprised of
strongly repulsive bosons with filling factors of less than one atom per
lattice site. The entry of vortices into the system is characterized by jumps
of 2 pi in the phase winding of the condensate wavefunction. A lattice of size
L X L can have at most L-1 quantized vortices in the lowest Bloch band. In
contrast to homogeneous systems, angular momentum is not a good quantum number
since the continuous rotational symmetry is broken by the lattice. Instead, a
quasi-angular momentum captures the discrete rotational symmetry of the system.
Energy level crossings indicative of quantum phase transitions are observed
when the quasi-angular momentum of the ground-state changes.
\\ ( , 796kb)
Paper: cond-mat/0607782
Date: Fri, 28 Jul 2006 23:35:32 GMT (22kb)

Title: BCS-BEC Crossover in the Strongly Correlated Regime of ultra-cold Fermi
Authors: S. G. Bhongale and S. J. J. M. F. Kokkelmans
Comments: 4 pages, 4 figures
Subj-class: Other; Mesoscopic Systems and Quantum Hall Effect
   We study BCS-BEC crossover in the strongly correlated regime of two component
rotating Fermi gases. We predict that the strong correlations induced by
rotation will have the effect of modifying the crossover region relative to the
non-rotating situation. We show via the two particle correlation function that
the crossover smoothly connects the s-wave paired fermionic fractional quantum
Hall state to the bosonic Laughlin state.
\\ ( , 22kb)
Paper: cond-mat/0607803
Date: Mon, 31 Jul 2006 15:41:12 GMT (286kb)

Title: BEC-BCS crossover, phase transitions and phase separation in polarized
   resonantly-paired superfluids
Authors: Daniel E. Sheehy, Leo Radzihovsky (University of Colorado)
Comments: 76 RevTeX pages, 54 figures
Subj-class: Superconductivity
   We study resonantly-paired s-wave superfluidity in a degenerate gas of two
species (hyperfine states labeled by $\uparrow,\downarrow$) of fermionic atoms
when the numbers $N_{\uparrow}$ and $N_{\downarrow}$ of the two species are
{\it unequal}, i.e., the system is "polarized". We find that the continuous
crossover from the Bose-Einstein condensate (BEC) limit of tightly-bound
diatomic molecules to the Bardeen-Cooper-Schrieffer (BCS) limit of weakly
correlated Cooper pairs, studied extensively at equal populations, is
interrupted by a variety of distinct phenomena under an imposed population
difference $\Delta N \equiv N_\uparrow - N_\downarrow$. Our findings are
summarized by a `` polarization\rq\rq ($\Delta N$) versus Feshbach-resonance
detuning ($\delta$) zero-temperature phase diagram, which exhibits regions of
phase separation, a periodic FFLO superfluid, a polarized normal Fermi gas and
a polarized molecular superfluid consisting of a molecular condensate and a
fully polarized Fermi gas. We describe numerous experimental signatures of such
phases and the transitions between them, in particular focusing on their
spatial structure in the inhomogeneous environment of an atomic trap.
\\ ( , 286kb)
Paper: cond-mat/0607821
Date: Mon, 31 Jul 2006 14:45:40 GMT (17kb)

Title: The unitary gas in an isotropic harmonic trap: symmetry properties and
Authors: F\'{e}lix Werner (LKB - Lhomond), Yvan Castin (LKB - Lhomond)
Proxy: ccsd ccsd-00088162
Subj-class: Other
   We consider N atoms trapped in an isotropic harmonic potential, with s-wave
interactions of infinite scattering length. In the zero-range limit, we obtain
several exact analytical results: mapping between the trapped problem and the
free-space zero-energy problem, separability in hyperspherical coordinates,
SO(2,1) hidden symmetry, and relations between the moments of the trapping
potential energy and the moments of the total energy.
\\ ( , 17kb)
Paper: cond-mat/0607828
Date: Mon, 31 Jul 2006 15:40:48 GMT (193kb)

Title: Partially incoherent gap solitons in Bose-Einstein condensates
Authors: I. M. Merhasin, Boris A. Malomed and Y. B. Band
Comments: 8 pages, 9 figures. Physical Review A, in press
Subj-class: Other
   We construct families of incoherent matter-wave solitons in a repulsive
degenerate Bose gas trapped in an optical lattice (OL), i.e., gap solitons, and
investigate their stability at zero and finite temperature, using the
Hartree-Fock-Bogoliubov equations. The gap solitons are composed of a coherent
condensate, and normal and anomalous densities of incoherent vapor co-trapped
with the condensate. Both intragap and intergap solitons are constructed, with
chemical potentials of the components falling in one or different bandgaps in
the OL-induced spectrum. Solitons change gradually with temperature. Families
of intragap solitons are completely stable (both in direct simulations, and in
terms of eigenvalues of perturbation modes), while the intergap family may have
a very small unstable eigenvalue (nevertheless, they feature no instability in
direct simulations). Stable higher-order (multi-humped) solitons, and bound
complexes of fundamental solitons are found too.
\\ ( , 193kb)
Paper: cond-mat/0607831
Date: Mon, 31 Jul 2006 17:15:48 GMT (473kb)

Title: Correlations in a BEC collision: First-principles quantum dynamics with
   150,000 atoms
Authors: P. Deuar and P. D. Drummond
Comments: 4 pages, 4 figures
Subj-class: Other
   The quantum dynamics of colliding Bose-Einstein condensates with 150,000
atoms are simulated directly from the Hamiltonian using the stochastic
positive-P method. Two-body correlations between the scattered atoms and their
velocity distribution are found for experimentally accessible parameters.
Hanbury-Brown-Twiss or thermal-like correlations are seen for co-propagating
atoms, while number correlations for counter-propagating atoms are even
stronger than thermal correlations at short times. The coherent phase-grains
grow in size as the collision progresses with the onset of growth coinciding
with the beginning of stimulated scattering. These results demonstrate that
exponentially complex calculations involving over 10^{1,000,000} quantum states
are feasible using existing computers. The method is versatile and usable for a
range of cold atom systems.
\\ ( , 473kb)
Paper: cond-mat/0607834
Date: Mon, 31 Jul 2006 18:24:35 GMT (219kb)

Title: Polarized fermions in the unitarity limit
Authors: Gautam Rupak, Thomas Schaefer, Andrei Kryjevski
Comments: 5 pages, 5 figures, LaTeX2e
Subj-class: Other
   We consider a polarized Fermi gas in the unitarity limit. Results are
calculated analytically up to next-to-leading order in an expansion about d=4
spatial dimensions. We find a first order transition from superfluid to normal
phase. The critical chemical potential asymmetry for this phase transition is
delta_mu_c= 2/(mu epsilon)*(1-0.467\epsilon), where epsilon=4-d is the
expansion parameter and 'mu' is the average chemical potential of the two
fermion species. Stability of the superfluid phase in the presence of
supercurrents is also studied.
\\ ( , 219kb)
Paper: cond-mat/0607835
Date: Mon, 31 Jul 2006 18:59:06 GMT (260kb)

Title: Fermi gas near unitarity around four and two spatial dimensions
Authors: Yusuke Nishida and Dam Thanh Son
Comments: 20 pages, 15 figures, revtex4
Report-no: INT-PUB 06-10, TKYNT-06-10
Subj-class: Other
   We construct systematic expansions around four and two spatial dimensions for
a Fermi gas near the unitarity limit. Near four spatial dimensions such a Fermi
gas can be understood as a weakly-interacting system of fermionic and bosonic
degrees of freedom. To the leading and next-to-leading orders in the expansion
over epsilon=4-d, with d being the dimensionality of space, we calculate the
thermodynamic quantities and the fermion quasiparticle spectrum as functions of
the binding energy of the two-body state. Then the phase structure of the
polarized Fermi gas near the unitarity regime is studied from the epsilon
expansion. We found that at unitarity there is a first-order phase transition
from the unpolarized superfluid state to a completely polarized normal state.
On the BEC side of the unitarity point, in a certain range of the two-body
binding energy we find a gapless superfluid phase and a superfluid phase with
spatially varying condensate which occupy a region in the phase diagram between
the gapped superfluid phase and the normal phase. We also show that the unitary
Fermi gas near two spatial dimensions reduces to a weakly-interacting Fermi gas
and calculate the thermodynamic quantities and the fermion quasiparticle
spectrum in the expansion over \bar\epsilon=d-2.
\\ ( , 260kb)
Paper: cond-mat/0607706
replaced with revised version Mon, 31 Jul 2006 17:17:33 GMT (139kb)

Title: Transistor-Like Behavior of a Bose-Einstein Condensate in a Triple Well
Authors: James A. Stickney, Dana Z. Anderson, and Alex A. Zozulya
Comments: 12 pages, 12 figures
Subj-class: Statistical Mechanics
\\ ( , 139kb)
Paper: quant-ph/0607218
Date: Sun, 30 Jul 2006 17:52:26 GMT (300kb)

Title: Quantum coherence and population trapping in three-photon processes
Authors: Caroline Champenois (PIIM), Giovanna Morigi (GRUP D'OPTICA), Juergen
   Eschner (ICFO)
Proxy: ccsd ccsd-00088084
   The spectroscopic properties of a single, tightly trapped atom are studied,
when the electronic levels are coupled by three laser fields in an $N$-shaped
configuration of levels, whereby a $\Lambda$-type level system is weakly
coupled to a metastable state. We show that depending on the laser frequencies
the response can be tuned from coherent population trapping at two-photon
resonance to novel behaviour at three photon resonance, where the metastable
state can get almost unit occupation in a wide range of parameters. For certain
parameter regimes the system switches spontaneously between dissipative and
coherent dynamics over long time scales.
\\ ( , 300kb)
Paper: physics/0607294
Date: Mon, 31 Jul 2006 16:45:18 GMT (811kb)

Title: Precision preparation of strings of trapped neutral atoms
Authors: Y. Miroshnychenko, W. Alt, I. Dotsenko, L. F\"orster, M. Khudaverdyan,
   A. Rauschenbeutel and D. Meschede
Comments: 25 pages, 18 figures
Subj-class: Atomic Physics
   We have recently demonstrated the creation of regular strings of neutral
caesium atoms in a standing wave optical dipole trap using optical tweezers [Y.
Miroshnychenko et al., Nature, in press (2006)]. The rearrangement is realized
atom-by-atom, extracting an atom and re-inserting it at the desired position
with sub-micrometer resolution. We describe our experimental setup and present
detailed measurements as well as simple analytical models for the resolution of
the extraction process, for the precision of the insertion, and for heating
processes. We compare two different methods of insertion, one of which permits
the placement of two atoms into one optical micropotential. The theoretical
models largely explain our experimental results and allow us to identify the
main limiting factors for the precision and efficiency of the manipulations.
Strategies for future improvements are discussed.
\\ ( , 811kb)
Paper: physics/0604140
replaced with revised version Mon, 31 Jul 2006 09:58:29 GMT (292kb)

Title: Theoretical model for ultracold molecule formation via adaptive feedback
Authors: Ulrich Poschinger, Wenzel Salzmann, Roland Wester, Matthias
   Weidemueller, Christiane P. Koch, Ronnie Kosloff
Subj-class: Atomic Physics
\\ ( , 292kb)
Paper: cond-mat/0608012
Date: Tue, 1 Aug 2006 06:29:30 GMT (138kb)

Title: Pfaffian-like ground state for 3-body-hard-core bosons in 1D lattices
Authors: B. Paredes, T. Keilmann, J. I. Cirac
Subj-class: Other
   We propose a Pfaffian-like Ansatz for the ground state of bosons subject to
3-body infinite repulsive interactions in a 1D lattice. Our Ansatz consists of
the symmetrization over all possible ways of distributing the particles in two
identical Tonks-Girardeau gases. We support the quality of our Ansatz with
numerical calculations and propose an experimental scheme based on mixtures of
bosonic atoms and molecules in 1D optical lattices in which this Pfaffian-like
state could be realized. Our findings may open the way for the creation of
non-abelian anyons in 1D systems.
\\ ( , 138kb)
Paper: cond-mat/0602622
replaced with revised version Tue, 1 Aug 2006 14:55:11 GMT (68kb)

Title: Anderson localization of elementary excitations in a one dimensional
   Bose-Einstein condensate
Authors: Nicolas Bilas and Nicolas Pavloff Comments: 11 pages, 6 figures. Final
printed version
Subj-class: Other
\\ ( , 68kb)
Paper: cond-mat/0608053
Date: Wed, 2 Aug 2006 16:56:14 GMT (38kb)

Title: Global singularity-free solution of the Iordanskii force problem
Authors: Markus Flaig and Uwe R. Fischer
Comments: 7 pages of RevTex4, 1 figure
Subj-class: Other
   We present a derivation of the transverse force acting on a hydrodynamic
vortex in the presence of an incoming sound wave from a global solution of the
scattering problem, using the method of matched asymptotic expansions. The
solution presented includes a detailed treatment of the interaction of the
incident wave with the vortex core, and is free from the singularities in the
momentum exchange between vortex and sound wave which have led to contradictory
results for the value of the transverse force in the literature.
\\ ( , 38kb)
Paper: cond-mat/0605039
replaced with revised version Wed, 2 Aug 2006 17:41:04 GMT (61kb)

Title: Intermediate temperature superfluidity in an atomic Fermi gas with
   population imbalance
Authors: Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin
Comments: 4 pages, 4 EPS figures, clarified the discussions about stability
   conditions, added a new inset to Fig.3
Subj-class: Strongly Correlated Electrons; Superconductivity
\\ ( , 61kb)
Paper: quant-ph/0309149
replaced with revised version Wed, 2 Aug 2006 13:59:30 GMT (159kb)

Title: Directed motion for delta-kicked atoms with broken symmetries:
comparison between theory and experiment
Authors: P. H. Jones, M. Goonasekera, D. R. Meacher, T. Jonckheere, T. S.
Comments: 5 pages, 5 figures Now includes experimental data on time evolution
   and comparison with theory
\\ ( , 159kb)
Paper: physics/0608021
Date: Wed, 2 Aug 2006 14:08:19 GMT (235kb)

Title: From Optical Lattice Clocks to the Measurement of Forces in the Casimir
Authors: Peter Wolf (LNE-SYRTE, BIPM), Pierre Lemonde (LNE-SYRTE), Astrid
   Lambrecht (LKB - Jussieu), Sebastien Bize (LNE-SYRTE), Arnaud Landragin
   (LNE-SYRTE), Andre Clairon (LNE-SYRTE)
Comments: 10 pages, to be published in the Proceedings of the 2006 IEEE
   Frequency Control Symposium
Proxy: ccsd ccsd-00088469
Subj-class: Atomic Physics
   We propose a novel experiment based on atoms trapped close to a macroscopic
surface, to study the interactions between the atoms and the surface at very
small separations (0.6 to 10 $\mu$m). In this range the dominant potential is
the QED interaction (Casimir-Polder and Van der Waals) between the surface and
the atom. Additionally, several theoretical models suggest the possibility of
Yukawa type potentials with sub-mm range, arising from new physics related to
gravity. We propose a set-up very similar to neutral atom optical lattice
clocks, but with the atoms trapped in lattice sites close to the reflecting
mirror. A sequence of pulses of the probe laser at different frequencies is
then used to create an interferometer with a coherent superposition between
atomic states at different distances from the mirror. Assuming state of the art
measurements, we expect that such an experiment would improve the best existing
measurements of the atom-wall QED interaction by &#8805;2 orders of magnitude,
whilst gaining up to 4 orders of magnitude on the best present limits on new
interactions in the range between 100 nm and 100 $\mu$m.
\\ ( , 235kb)
Paper: cond-mat/0608091
Date: Thu, 3 Aug 2006 15:37:09 GMT (35kb)

Title: Modulation spectroscopy with ultracold fermions in an optical lattice
Authors: C. Kollath, A. Iucci, I. McCulloch, and T. Giamarchi Subj-class:
   We propose an experimental setup of ultracold fermions in an optical lattice
to determine the pairing gap in a superfluid state and the spin ordering in a
Mott-insulating state. The idea is to apply a periodic modulation of the
lattice potential and to use the thereby induced double occupancy to probe the
  We show by full time-dependent calculation using the adaptive time dependent
density-matrix renormalization group method that the position of the peak in
the spectrum of the induced double occupancy gives the pairing energy in a
superfluid and the interaction energy in a Mott-insulator, respectively. In the
Mott-insulator we relate the spectral weight of the peak to the spin ordering
at finite temperature using perturbative calculations.
\\ ( , 35kb)
Paper: cond-mat/0603721
replaced with revised version Thu, 3 Aug 2006 15:54:43 GMT (52kb)

Title: Spectroscopy of ultracold atoms by periodic lattice modulations
Authors: C. Kollath, A. Iucci, T. Giamarchi, W. Hofstetter, U. Schollwoeck
Subj-class: Other
Journal-ref: Phys. Rev. Lett. 97, 050402 (2006)
DOI: 10.1103/PhysRevLett.97.050402
\\ ( , 52kb)
Paper: physics/0608024
Date: Wed, 2 Aug 2006 20:58:45 GMT (415kb)

Title: Analysis of a Magnetically Trapped Atom Clock
Authors: D. Kadio and Y.B. Band Comments: 11 pages, 6 figures. Accepted for
publication in Phys. Rev. A
Subj-class: Atomic Physics
   We consider optimization of a rubidium atom clock that uses magnetically
trapped Bose condensed atoms in a highly elongated trap, and determine the
optimal conditions for minimum Allan variance of the clock using microwave
Ramsey fringe spectroscopy. Elimination of magnetic field shifts and
collisional shifts are considered. The effects of spin-dipolar relaxation are
addressed in the optimization of the clock. We find that a modulational
instability results in phase separation and symmetry breaking of the
two-component condensate composed of the ground and excited hyperfine clock
levels, and this mechanism limits the clock accuracy.
\\ ( , 415kb)
Paper: cond-mat/0603334
replaced with revised version Fri, 4 Aug 2006 08:25:51 GMT (33kb)

Title: Phases of Bosons or Fermions in confined optical lattices
Authors: H. Heiselberg
Comments: Revised and extended. To appear in PRA
Subj-class: Superconductivity
\\ ( , 33kb)
Paper: cond-mat/0604671
replaced with revised version Fri, 4 Aug 2006 08:48:40 GMT (678kb)

Title: Theory of Ultracold Superstrings
Authors: Michiel Snoek, S. Vandoren, and H.T.C. Stoof
Comments: 16 pages, 9 figures, important factor 2 corrected, accepted for
   publication in PRA
Subj-class: Other
\\ ( , 678kb)
Paper: cond-mat/0606243
replaced with revised version Fri, 4 Aug 2006 12:08:47 GMT (304kb)

Title: A 'Wheel' and 'Axle' description of the Bogoliubov-Anderson phonon in
   the BEC/BCS crossover
Authors: Da-Shin Lee, Chi-Yong Lin and Ray J. Rivers
Comments: Four pages, 2 figures. The new version contains additional references
   and comments, but is unchanged in all other regards
Subj-class: Other
\\ ( , 304kb)
Paper: physics/0604026
replaced with revised version Fri, 4 Aug 2006 00:18:22 GMT (576kb)

Title: Electromagnetically Induced Transparency in 6Li
Authors: J. Fuchs, G. J. Duffy, W. J. Rowlands and A. M. Akulshin
Comments: 12 pages, 9 figures
Subj-class: Atomic Physics
\\ ( , 576kb)
Paper: cond-mat/0608135
Date: Sat, 5 Aug 2006 05:18:20 GMT (388kb)

Title: Disruption of reflecting Bose-Einstein condensates due to quantum noise
   and modulational instability
Authors: R.G. Scott, D.A.W. Hutchinson and C.W. Gardiner
Comments: 5 figures
Subj-class: Other
   We perform fully three-dimensional simulations, using the truncated Wigner
method, to investigate the reflection of Bose-Einstein condensates from abrupt
potential barriers. We show that the inter-atomic interactions can produce a
modulational instability in a cigar-shaped cloud with a high atom density at
low approach velocities, disrupting its internal structure, damping the
center-of-mass motion and generating vortices. Furthermore, by incorporating
quantum noise we show that scattering halos form at high approach velocities,
causing an associated condensate depletion. We compare our results to recent
experimental observations.
\\ ( , 388kb)
Paper: cond-mat/0608154
Date: Mon, 7 Aug 2006 07:46:32 GMT (16kb)

Title: Pairing and Superfluid Properties of Dilute Fermion Gases at Unitarity
Authors: Vamsi K. Akkineni, D.M. Ceperley, Nandini Trivedi
Comments: 4 pages, 4 figures, To be submitted to PRL
Subj-class: Statistical Mechanics; Superconductivity
   We study the system of a dilute gas of fermions in 3-dimensions, with
attractive interactions tuned to the unitarity point, using the
non-perturbative Restricted Path Integral Monte Carlo (R-PIMC) method. The
pairing and superfluid properties of this system are calculated at finite
temperature. The total energy at very low temperature from our results agrees
closely with that of previous ground-state Quantum Monte Carlo calculations. We
identify the temperature $T^\ast\approx 0.70\epsilon_F$ below which pairing
correlations develop, and estimate the critical temperature for the superfluid
transition $T_c\approx 0.25\epsilon_F$ from a finite size scaling analysis of
the superfluid density.
\\ ( , 16kb)
Paper: cond-mat/0608171
Date: Mon, 7 Aug 2006 16:23:56 GMT (67kb)

Title: Comparing contact and dipolar interaction in a Bose-Einstein condensate
Authors: Axel Griesmaier, J\"urgen Stuhler, Tobias Koch, Marco Fattori, Tilman
   Pfau, and Stefano Giovanazzi Subj-class: Other
   We have measured the relative strength $\epsilon_dd$ of the magnetic
dipole-dipole interaction compared to the contact interaction in a chromium
Bose-Einstein condensate. We analyze the asymptotic velocities of expansion of
a dipolar chromium BEC with different orientations of the atomic magnetic
dipole moments. By comparing them with numerical solutions of the hydrodynamic
equations for dipolar condensates, we are able to determine $\epsilon_dd =
0.159\pm0.034$ with high accuracy. Since the absolute strength of the
dipole-dipole interaction is known exactly, the relative strength of the
dipoledipole interaction can be used to determine the s-wave scattering length
$a = 5.08\pm1.06\cdot10^-9 m = 96\pm20 a0$ of 52Cr. This is fully consistent
with our previous measurements on the basis of Feshbach resonances.
\\ ( , 67kb)
Paper: cond-mat/0608172
Date: Mon, 7 Aug 2006 17:50:36 GMT (38kb)

Title: Comment on "Superfluid stability in the BEC-BCS crossover" by C.-H. Pao,
   S.-T. Wu, and S.-K.-Yip
Authors: Daniel E. Sheehy and Leo Radzihovsky (University of Colorado)
Comments: 4 pages, 2 figures, submitted to Physical Review B
Subj-class: Superconductivity
   We point out an error in recent work by Pao et al [Phys. Rev.B {\bf 73},
132506 (2006)], that stems from their use of a necessary but not sufficient
condition [positive compressibility (magnetic susceptibility) and superfluid
stiffness] for the stability of the ground state of a polarized Fermi gas. As a
result, for a range of detunings their proposed ground-state solution is a
local maximum rather than a minimum of the ground state energy, which thereby
invalidates their proposed phase diagram for resonantly interacting fermions
under an imposed population difference.
\\ ( , 38kb)
Paper: cond-mat/0604500
replaced with revised version Fri, 4 Aug 2006 21:46:27 GMT (88kb)

Title: Epsilon expansion for a Fermi gas at infinite scattering length Authors:
Yusuke Nishida and Dam Thanh Son
Comments: 4 pages, 4 figures, revtex4; version to appear in Phys. Rev. Lett
Report-no: INT-PUB 06-08, TKYNT-06-06
Subj-class: Other
Journal-ref: Phys. Rev. Lett. 97, 050403 (2006)
DOI: 10.1103/PhysRevLett.97.050403
\\ ( , 88kb)
Paper: cond-mat/0606353
replaced with revised version Mon, 7 Aug 2006 04:54:37 GMT (222kb)
Title: Generalized exclusion statistics and degenerate signature of strongly
   interacting anyons
Authors: M T Batchelor and X W Guan
Comments: 7 pages, 3 figures, expanded version
Subj-class: Statistical Mechanics; Strongly Correlated Electrons
\\ ( , 222kb)
Paper: physics/0608074
Date: Mon, 7 Aug 2006 16:26:41 GMT (63kb)

Title: Measurement of the Temperature Dependence of the Casimir-Polder Force
Authors: J.M. Obrecht, R.J. Wild, M. Antezza, L.P. Pitaevskii, S. Stringari,
   E.A. Cornell
Comments: 4 pages, 4 figures, submitted to Physical Review Letters
Subj-class: Atomic Physics
   We report on the first measurement of a temperature dependence of the
Casimir-Polder force. This measurement was obtained by positioning a nearly
pure 87-Rb Bose-Einstein condensate a few microns from a dielectric substrate
and exciting its dipole oscillation. Changes in the collective oscillation
frequency of the magnetically trapped atoms result from spatial variations in
the surface-atom force. In our experiment, the dielectric substrate is heated
up to 605 K, while the surrounding environment is kept near room temperature
(310 K). The effect of the Casimir-Polder force is measured to be nearly three
times larger for a 605 K substrate than for a room-temperature substrate,
showing a clear temperature dependence in agreement with theory.
\\ ( , 63kb)
Paper: physics/0608058
Date: Sat, 5 Aug 2006 06:19:58 GMT (521kb)

Title: Cinema, Fermi Problems, & General Education
Authors: C.J. Efthimiou, R. Llewellyn
Comments: 15 pages
Subj-class: Physics Education; Physics and Society; Popular Physics
   During the past several years the authors have developed a new approach to
the teaching of Physical Science, a general education course typically found in
the curricula of nearly every college and university. This approach, called
`Physics in Films', uses scenes from popular movies to illustrate physical
principles and has excited student interest and improved student performance.
   The analyses of many of the scenes in `Physics in Films' are a direct
application of Fermi calculations -- estimates and approximations designed to
make solutions of complex and seemingly intractable problems understandable to
the student non-specialist. The intent of this paper is to provide instructors
with examples they can use to develop skill in recognizing Fermi problems and
making Fermi calculations in their own courses.
\\ ( , 521kb)
Paper: physics/0608060
Date: Sat, 5 Aug 2006 10:27:45 GMT (412kb)

Title: Matter-wave soliton control in optical lattices with topological
Authors: Yaroslav V. Kartashov, Lluis Torner
Comments: 15 pages, 4 figures, to appear in Physical Review A
Subj-class: Optics
   We address the concept of guiding and transporting matter-wave solitons along
the channels of optical lattices made by interference patterns of beams
containing topological wavefront dislocations. The local lattice distortions
that occur around the dislocations cause solitons to move along reconfigurable
paths, a phenomenon that may be used for controlled all-optical manipulation of
Bose-Einstein condensates. Multiple dislocations form traps that can capture
and hold moving solitons. \\ ( , 412kb)
Paper: physics/0407064
replaced with revised version Mon, 7 Aug 2006 07:02:52 GMT (849kb)

Title: First observation of feshbach resonances at very low magnetic field in a
   133Cs fountain
Authors: H. Marion (SYRTE), S. Bize (SYRTE), L. Cacciapuoti (SYRTE), D. Chambon
   (SYRTE), F. Pereira Dos Santos (SYRTE), G. Santarelli (SYRTE), P. Wolf
   (SYRTE), A. Clairon (SYRTE), A. Luiten (UWA), M. Tobar (UWA), S. Kokkelmans
   (LKB - Lhomond), C. Salomon (LKB - Lhomond)
Comments: 7 pages
Proxy: ccsd ccsd-00002196
Subj-class: Atomic Physics; Other
\\ ( , 849kb)
Paper: cond-mat/0603469
replaced with revised version Tue, 8 Aug 2006 05:09:36 GMT (167kb)

Title: Dissociation dynamics of resonantly coupled bose-fermi mixtures in an
   optical lattice
Authors: Takahiko Miyakawa and Pierre Meystre
Comments: 10 pages, 10 figures
Subj-class: Other
\\ ( , 167kb)
Paper: physics/0608083
Date: Mon, 7 Aug 2006 23:52:58 GMT (301kb)

Title: Atom interferometry in a moving guide
Authors: Saijun Wu, Edward J. Su, Mara Prentiss
Comments: 16 pages, 4 figures
Subj-class: Atomic Physics; Optics
   We demonstrate a current-controlled magnetic guide that can transport atoms
in the direction perpendicular to the waveguide. We have combined this with a
light pulse Talbot-Lau interferometer that splits and recombines atom
wavepackets along the free propagation direction of the waveguide, resulting in
an interferometric path that encloses area and thus can be used to sense
\\ ( , 301kb)
Paper: physics/0608088
Date: Tue, 8 Aug 2006 09:41:32 GMT (584kb)

Title: Pulsed evaporative cooling in a radio-frequency trap
Authors: Carlos L. Garrido Alzar (1), H\'el\`ene Perrin (1), Barry M. Garraway
   (2), Vincent Lorent (1) ((1) Laboratoire de Physique des Laser,
   CNRS-Universit\'e Paris 13, Villetaneuse, France, (2) Department of Physics
   and Astronomy, University of Sussex, Brighton, United Kingdom) Comments: 11
pages, 11 figures
Subj-class: Atomic Physics
   A theoretical investigation of forced evaporative cooling in radio-frequency
(rf) adiabatic potentials is presented. Supposing the atoms to be trapped by a
rf field RF1, the cooling procedure is developed around a second RF2
radio-frequency source. This second rf field forces the spin state dressed by
RF1 to adiabatically follow a time-evolving quantization axis. The evaporation
is then possible by quenching the adiabatic following spin dynamics. Our
results show that when the frequencies of RF1 and RF2 are comparable,
counter-intuitive evaporation zones appear making this process more efficient.
On the other hand, because of beating between the two rf signals, a pulsed
evaporative cooling scheme seems to be the optimal strategy to reduce the
temperature of the rf-trapped atoms.
\\ ( , 584kb)
Paper: physics/0604139
replaced with revised version Tue, 8 Aug 2006 13:51:44 GMT (118kb)

Title: Efficient formation of strongly bound ultracold cesium molecules by
   photoassociation with tunneling
Authors: Mihaela Vatasescu, Claude M. Dion, and Olivier Dulieu
Comments: 15 pages with 7 figures
Subj-class: Atomic Physics; Chemical Physics
\\ ( , 118kb)
Paper: cond-mat/0608216
Date: Wed, 9 Aug 2006 14:18:41 GMT (10kb)

Title: Non-uniform vortex lattices in inhomogeneous rotating Bose-Einstein
Authors: Gordon Baym, C. J. Pethick, S. Andrew Gifford, Gentaro Watanabe
Comments: 6 pages, no figures
Report-no: NORDITA-2006-20
Subj-class: Statistical Mechanics
   We derive a general framework, in terms of elastic theory, for describing the
distortion of the vortex lattice in a rotating Bose-Einstein condensate at
arbitrary rotation speed and determining the dependence of the distortion on
the density inhomogeneity of the system. In the rapidly rotating limit, we
derive the energetics in terms of Landau levels, including excitation to higher
levels; the distortion depends on the excitation of higher levels as well as on
the density gradient. As we show, the dominant effect of higher Landau levels
in a distorted lattice in equilibrium is simply to renormalize the frequency
entering the lowest Landau level condensate wave function -- from the
transverse trap frequency, $\omega$, to the rotational frequency, $\Omega$, of
the system. Finally, we show how the equilibrium lattice distortion emerges
from elastohydrodynamic theory for inhomogeneous systems.
\\ ( , 10kb)
Paper: cond-mat/0607412
replaced with revised version Wed, 9 Aug 2006 14:46:49 GMT (6kb)

Title: Bose-Einstein Condensation and Casimir Effect of Trapped Ideal Bose Gas
   in between two Slabs
Authors: Shyamal Biswas
Comments: 4 pages
Subj-class: Statistical Mechanics
\\ ( , 6kb)
Paper: quant-ph/0603054
replaced with revised version Wed, 9 Aug 2006 15:33:42 GMT (183kb)

Title: Elastic vs. inelastic coherent backscattering of laser light by cold
   atoms: a master equation treatment
Authors: Vyacheslav Shatokhin, Cord A. M\"uller, Andreas Buchleitner
Comments: 14 pages, 6 figures
Journal-ref: PRA 73, 063813 (2006)
\\ ( , 183kb)
Paper: cond-mat/0608233
Date: Wed, 9 Aug 2006 22:37:21 GMT (422kb)

Title: Critical Rotating Frequency for Superfluid Fermionic Gases across
   Feshbach Resonance
Authors: Hui Zhai and Tin-Lun Ho
Comments: 4 pages, 2 figures
Subj-class: Superconductivity
   We present a method to determine the critical rotational frequencies for
superfluidity of both uniform and trapped Fermi gases across wide Feshbach
resonance. It is found that as one approaches the resonance from the BCS side,
beyond a critical scattering length, pairing is so robust that superfluidity
cannot be destroyed by rotation. Moreover, the critical frequency has a
sequence of jumps revealing the appearance of Landau levels, which are
particularly prominent for systems up to a few thousand particles. For
rotational frequency below an "ultimate" critical frequency, defined to be the
lowest frequency at which the center of the cloud goes normal, a trapped gas
has a superfluid core surrounded by a normal gas, as seen in recent
\\ ( , 422kb)
Paper: cond-mat/0608246
Date: Thu, 10 Aug 2006 17:39:04 GMT (52kb)

Title: Quantum phase transition in a two-dimensional system of dipoles
Authors: G.E. Astrakharchik, J. Boronat, I.L. Kurbakov, Yu.E. Lozovik
Comments: 4 figures
Subj-class: Superconductivity
   The ground-state phase diagram of a two-dimensional Bose system with
dipole-dipole interactions is studied by means of quantum Monte Carlo
technique. Our calculation predicts a quantum phase transition from gas to
solid phase when the density increases. In the gas phase the condensate
fraction is calculated as a function of the density. Using Feynman
approximation, the collective excitation branch is studied and appearance of a
roton minimum is observed. Results of the static structure factor at both sides
of the gas-solid phase are also presented. The Lindeman ratio at the transition
point comes to be $\gamma = 0.230(6)$. The condensate fraction in the gas phase
is estimated as a function of the density.
\\ ( , 52kb)
Paper: cond-mat/0608247
Date: Thu, 10 Aug 2006 16:14:44 GMT (276kb)

Title: Fluctuation statistics of mesoscopic Bose-Einstein condensate:
   reconciling the master equation with the partition function to revisit the
   Uhlenbeck-Einstein dilemma
Authors: Andrew N. Jordan, C. H. Raymond Ooi, Anatoly A. Svidzinsky
Comments: 13 pages, 6 figures
Subj-class: Other; Statistical Mechanics
   The atom fluctuations statistics of an ideal, mesoscopic, Bose-Einstein
condensate is investigated from several different perspectives. By generalizing
the grand canonical analysis (applied to the canonical ensemble problem), we
obtain a self-consistent equation for the mean condensate particle number that
coincides with the microscopic result calculated from the laser master equation
approach. For the case of a harmonic trap, we obtain an analytic expression for
the condensate particle number that is very accurate at all temperatures, when
compared with numerical canonical ensemble results. Applying a similar
generalized grand canonical treatment to the variance, we obtain an accurate
result only below the critical temperature. Analytic results are found for all
higher moments of the fluctuation distribution by employing the stochastic path
integral formalism, with excellent accuracy. We further discuss a hybrid
treatment, which weds the master equation/stochastic path integral analysis
with the results obtained based on canonical ensemble quasiparticle formalism
[V. V. Kocharovsky et al., Phys. Rev. A 61, 053606 (2000)], producing
essentially perfect agreement with numerical simulation at all temperatures.
\\ ( , 276kb)
Paper: quant-ph/0608089
Date: Thu, 10 Aug 2006 07:34:34 GMT (189kb)

Title: Efficient coherent internal state transfer in trapped ions using
   Stimulated Raman Adiabatic Passage
Authors: Jens L. S{\o}rensen, Ditte M{\o}ller, Theis Iversen, Jakob B. Thomsen,
   Frank Jensen, Peter Staanum, Dirk Voigt, Michael Drewsen
Comments: 4 pages, 3 figures
   We demonstrate experimentally how the process of Stimulated Raman Adiabatic
Passage (STIRAP) can be utilized for efficient coherent internal state transfer
in single trapped and laser-cooled $^{40}$Ca$^+$ ions. The transfer from the
D$_{3/2}$ to the D$_{5/2}$ state, is detected by a fluorescence measurement
revealing the population not transfered to the D$_{5/2}$ state. A coherent
population transfer efficiency at the level of 95 % in a setup allowing for the
internal state detection of individual ions in a string has been obtained.
\\ ( , 189kb)
Paper: cond-mat/0608250
Date: Thu, 10 Aug 2006 20:06:59 GMT (28kb)

Title: Quantum fluids of self-assembled chains of polar molecules
Authors: Daw-Wei Wang, Mikhail D. Lukin, and Eugene Demler
Comments: 5 pages and 3 figures
Subj-class: Other; Soft Condensed Matter
   We study polar molecules in a stack of strongly confined pancake traps. When
dipolar moments point perpendicular to the planes of the traps and are
sufficiently strong, the system is stable against collapse but attractive
interaction between molecules in different layers leads to the formation of
extended chains of molecules, analogously to the chaining phenomenon in
classical rheological electro- and magnetofluids. We analyze properties of the
resulting quantum liquid of dipolar chains and show that only the longest
chains undergo Bose-Einstein condensation with a strongly reduced condensation
temperature. We discuss several experimental methods for studying chains of
dipolar molecules.
\\ ( , 28kb)
Paper: cond-mat/0608255
Date: Fri, 11 Aug 2006 18:59:50 GMT (261kb)

Title: FFLO Vortex Lattice States in Cold Fermionic-Atom Systems
Authors: Y.-P. Shim, R. A. Duine, and A. H. MacDonald
Comments: 10 pages, 9 figures
Subj-class: Statistical Mechanics
   Condensation of atom pairs with finite total momentum is expected in a
portion of the phase diagram of a two-component fermionic cold-atom system.
This unusual condensate can be identified by detecting the exotic higher Landau
level (HLL) vortex lattice states it can form when rotated. With this
motivation, we have solved the linearized gap equations of a polarized cold
atom system in a Landau level basis to predict experimental circumstances under
which HLL vortex lattice states occur.
\\ ( , 261kb)
Paper: cond-mat/0608258
Date: Fri, 11 Aug 2006 04:08:43 GMT (151kb)

Title: Vortex Properties of a Resonant Superfluid
Authors: Meng Gao, Hongyu Wu, Lan Yin
Comments: 13 pages, 10 figures
Subj-class: Other
Journal-ref: Phys. Rev. A 74, 023604 (2006)
   The properties of a vortex in a rotating superfluid Fermi gas are studied in
the unitary limit. A phenomenological approach based on Ginzburg-Landau theory
is developed for this purpose. The density profiles, including those of the
normal fluid and superfluid, are obtained at various temperatures and rotation
frequencies. The superfluid and normal fluid densities can be identified from
the angular momentum density. The total free energy and angular momentum of the
vortex are also obtained.
\\ ( , 151kb)
Paper: cond-mat/0608262
Date: Fri, 11 Aug 2006 11:52:55 GMT (123kb)

Title: Quantum Phase Transition in Ultracold 87Rb Atom Gas with Radiant Field
Authors: Gang Chen, J.-Q. Liang, W.-M. Liu
Comments: 3 figures
Subj-class: Strongly Correlated Electrons
   A second-order quantum phase transition in two-species Bose-Einstein
condensates of 87Rb atoms coupled by a quantized radiant field is revealed
explicitly in terms of the energy spectrum which is obtained in the
thermodynamic limit and is controllable by the coupling parameter between the
atom and field. The scaling behavior of the collective excitation modes at the
critical transition point is seen to be in the same universality class as that
of the Dicke model. It is also demonstrated that the quantum phase transition
is realizable below the critical temperature of BEC and can be detected
experimentally by measuring the abrupt change of atom population imbalance.
\\ ( , 123kb)
Paper: cond-mat/0608265
Date: Fri, 11 Aug 2006 12:51:53 GMT (14kb)

Title: 1/N-Expansion and the Dilute Bose Gas Beyond Mean-field Theory
Authors: Jens O. Andersen
Comments: 6 pages, 3 figs
Subj-class: Other
   We consider the nonrelativistic interacting Bose gas at zero and finite
temperature. Using the 1/N-expansion, we derive expressions for the free energy
density and the number density to next-to-leading order in 1/N. Outside the
critical region and at weak coupling, our calculations reduce to the well-known
mean-field results for the dilute Bose gas. We also rederive the
nonperturbative critical density for Bose condensation which was first
calculated by Baym, Blaizot, Holzmann, Lal\"oe, and Vautherin.
\\ ( , 14kb)
Paper: cond-mat/0608282
Date: Fri, 11 Aug 2006 18:59:01 GMT (395kb)

Title: Thermodynamics of the BCS-BEC crossover
Authors: R. Haussmann, W. Rantner, S. Cerrito and W. Zwerger
Comments: 27 pages, 16 figures, submitted to PRA
Subj-class: Statistical Mechanics
   We present a self-consistent and conserving theory for the thermodynamics of
the BCS-BEC crossover, both in the normal and superfluid phase. It is based on
the variational many-body formalism developed by Luttinger and Ward and by
DeDominicis and Martin. Truncating the exact functional for the entropy to that
obtained within a ladder approximation, the resulting self-consistent integral
equations for the normal and anomalous Green functions are solved numerically
for arbitrary coupling. The critical temperature, the equation of state and the
entropy are determined as a function of the dimensionless parameter $1/k_Fa$,
which controls the crossover from the BCS-regime of extended pairs to the
BEC-regime of tightly bound molecules. The tightly bound pairs turn out to be
described by a Popov-type approximation for a dilute, repulsive Bose-gas. The
superfluid transition in our approximation is weakly first order, in contrast
to the expected continuous transition. In spite of this problem, our results
compare well with a recent numerically exact solution of the problem at the
unitarity point.
   The results allow to determine the temperature dependence of the cloud size
in a harmonic trap and the temperatures reached in an isentropic ramp of the
magnetic field across a Feshbach resonance, as studied experimentally.
\\ ( , 395kb)
Paper: quant-ph/0608099
Date: Fri, 11 Aug 2006 11:58:26 GMT (38kb)

Title: Uniform semiclassical approximations of the nonlinear Schroedinger
   equation by a Painleve mapping
Authors: D. Witthaut and H. J. Korsch
   A useful semiclassical method to calculate eigenfunctions of the Schroedinger
equation is the mapping to a well-known ordinary differential equation, as for
example Airy's equation. In this paper we generalize the mapping procedure to
the nonlinear Schroedinger equation or Gross-Pitaevskii equation describing the
macroscopic wave function of a Bose-Einstein condensate. The nonlinear
Schroedinger equation is mapped to the second Painleve equation, which is one
of the best-known differential equations with a cubic nonlinearity. A
quantization condition is derived from the connection formulae of these
functions. Comparison with numerically exact results for a harmonic trap
demonstrates the benefit of the mapping method. Finally we discuss the
influence of a shallow periodic potential on bright soliton solutions by a
mapping to a constant potential.
\\ ( , 38kb)

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
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Received on Tue Aug 15 2006 - 02:11:30 EST

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