Matt's arXiv selection, Monday 24th July 2006.

From: Matthew Davis <>
Date: Tue, 25 Jul 2006 02:18:55 +1000 (EST)

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

Hi all,

This week I would like to offer my apologies to Griessner et al., whom it seems
I left out of my last arXiv mailing. Therefore their paper comes first this
week. If anyone notices that I miss your relevant paper, kindly let me know and
it will take pride of place the following week.

I am officially on holiday next week, but the arXiv mailing should still go

The abstracts:

Paper: cond-mat/0607254
Date: Mon, 10 Jul 2006 20:10:42 GMT (129kb)
Title: Dark state cooling of atoms by superfluid immersion
Authors: A. Griessner, A. J. Daley, S. R. Clark, D. Jaksch, and P. Zoller
Comments: 4 pages, 4 figures, RevTeX 4
Subj-class: Other
   We propose and analyse a scheme to cool atoms in an optical lattice to
ultra-low temperatures within a Bloch band, and away from commensurate filling.
The protocol is inspired by ideas from dark state laser cooling, but replaces
electronic states with motional levels, and spontaneous emission of photons by
emission of phonons into a Bose-Einstein condensate, in which the lattice is
immersed. In our model, achievable temperatures correspond to a small fraction
of the Bloch band width, and are much lower than the reservoir temperature.
\\ ( , 129kb)
Paper: cond-mat/0607320
Date: Thu, 13 Jul 2006 17:07:58 GMT (5kb)

Title: Hydrodynamics of Superfluid Bose Gases in an Optical Lattice at Finite
Authors: Satoru Konabe and Tetsuro Nikuni
Comments: 6pages, submitted to Quantum Fluids and Solids Conference (QFS 2006)
Subj-class: Other
   Starting from an effective action for the order parameter field, we derive a
coupled set of generalized hydrodynamic equations for a Bose condensate in an
optical lattice at finite temperatures. Using the linearized hydrodynamic
equations, we study the microscopic mechanism of the Landau instability due to
the collisional damping process between condensate and noncondensate atoms. It
is shown that the Landau criterion of the superfluidity for the uniform system
is modified due to the presence of the periodic optical lattice potential.
\\ ( , 5kb)
Paper: cond-mat/0607328
Date: Thu, 13 Jul 2006 12:31:10 GMT (345kb)

Title: Bose-Einstein condensation of strongly correlated electrons and phonons
   in cuprate superconductors
Authors: A.S. Alexandrov
Comments: 35 pages, 10 figures, invited paper for the special volume of Journal
   of Physics: Condensed Matter
Subj-class: Superconductivity; Strongly Correlated Electrons
   The long-range Froehlich electron-phonon interaction has been identified as
the most essential for pairing in high-temperature superconductors owing to
poor screening, as is now confirmed by optical, isotope substitution, recent
photoemission and some other measurements. I argue that low energy physics in
cuprate superconductors is that of superlight small bipolarons, which are
real-space hole pairs dressed by phonons in doped charge-transfer Mott
insulators. They are itinerant quasiparticles existing in the Bloch states at
low temperatures as also confirmed by continuous-time quantum Monte-Carlo
algorithm (CTQMC) fully taking into account realistic Coulomb and long-range
Froehlich interactions. Here I suggest that a parameter-free evaluation of Tc,
unusual upper critical fields, the normal state Nernst effect, diamagnetism,
the Hall-Lorenz numbers and giant proximity effects strongly support the
three-dimensional (3D) Bose-Einstein condensation of mobile small bipolarons
with zero off-diagonal order parameter above the resistive critical temperature
$T_c$ at variance with phase fluctuation scenarios of cuprates.
\\ ( , 345kb)
Paper: cond-mat/0607331
Date: Thu, 13 Jul 2006 13:38:56 GMT (15kb)

Title: Semiclassical corrections to the interaction energy of a hard-sphere
   Boltzmann gas
Authors: R. K. Bhaduri, W. van Dijk, and M. K. Srivastava
Comments: 9 pages, 3 figures, submitted to Eur. J. Phys
Subj-class: Statistical Mechanics
   Quantum effects in statistical mechanics are important when the thermal
wavelength is of the order of, or greater than, the mean interatomic spacing.
This is examined at depth taking the example of a hard-sphere Boltzmann gas.
Using the virial expansion for the equation of state, it is shown that the
interaction energy of a classical hard-sphere gas is exactly zero. When the
(second) virial coefficient of such a gas is obtained quantum mechanically,
however, the quantum contribution to the interaction energy is shown to be
substantial. The importance of the semiclassical corrections to the interaction
energy shows up dramatically in such a system.
\\ ( , 15kb)
Paper: cond-mat/0607332
Date: Thu, 13 Jul 2006 13:50:28 GMT (48kb)

Title: Quantum effects in the dynamical localization of Bose-Einstein
   condensates in optical lattices
Authors: Beata J. Dabrowska-Wuester, Sebastian Wuester, Ashton S. Bradley,
   Matthew J. Davis and Elena A. Ostrovskaya
Subj-class: Other
   We study quantum effects in the dynamics of a Bose-Einstein condensate loaded
onto the edge of a Brillouin zone of a one-dimensional periodic potential
created by an optical lattice. We show that quantum fluctuations trigger the
dynamical instability of the Bloch states of the condensate and can lead to the
generation of arrays of matter-wave gap solitons. Our approach also allows us
to study the instability-induced anomalous heating of the condensate at the
edge of the Brillouin zone and growth of the uncondensed atomic fraction. We
demonstrate that there are regimes in which the heating effects do not suppress
the formation of the localised states. We show that a phase imprinting
technique can ensure the formation of gap soliton trains after short evolution
times and at fixed positions.
\\ ( , 48kb)
Paper: cond-mat/0607334
Date: Thu, 13 Jul 2006 15:33:41 GMT (63kb)

Title: Bragg Spectroscopy of Cold Atomic Fermi Gases
Authors: G. M. Bruun, Gordon Baym
Comments: 8 pages, 9 figures
Subj-class: Superconductivity
   We propose a Bragg spectroscopy experiment to measure the onset of superfluid
pairing in ultracold trapped Fermi gases. In particular, we study two component
Fermi gases in the weak coupling BCS and BEC limits as well as in the strong
coupling unitarity limit. The low temperature Bragg spectrum exhibits a gap
directly related to the pair-breaking energy. Furthermore, he Bragg spectrum
has a large maximum just below the critical temperature when the gas is
superfluid in the BCS limit. In the unitarity regime, we show how the pseudogap
in the normal phase leads to a significant suppression of the low frequency
Bragg spectrum.
\\ ( , 63kb)
Paper: cond-mat/0607340
Date: Thu, 13 Jul 2006 19:15:08 GMT (584kb)

Title: Hyperspherical Description of the Degenerate Fermi Gas: S-wave
Authors: Seth T. Rittenhouse (1), M. J. Cavagnero (2), Javier von Stecher (1),
   Chris H. Greene (1) ((1)University of Colorado, (2) University of Kentucky)
Subj-class: Other
   We present a unique theoretical description of the physics of the spherically
trapped $N$-atom degenerate Fermi gas (DFG) at zero temperature based on an
ordinary Schr\"{o}dinger equation with a microscopic, two body interaction
potential. With a careful choice of coordinates and a variational wavefunction,
the many body Schr\"{o}dinger equation can be accurately described by a
\emph{linear}, one dimensional effective Schr\"{o}dinger equation in a single
collective coordinate, the rms radius of the gas. Comparisons of the energy,
rms radius and peak density of ground state energy are made to those predicted
by Hartree-Fock (HF). Also the lowest radial excitation frequency (the
breathing mode frequency) agrees with a sum rule calculation, but deviates from
a HF prediction.
\\ ( , 584kb)
Paper: cond-mat/0512472
replaced with revised version Thu, 13 Jul 2006 08:51:36 GMT (72kb)

Title: Fermionic superfluidity with positive scattering length
Authors: Bout Marcelis and Servaas Kokkelmans
Comments: 6 pages, 3 figures; v2: added references and details energy-dependent
Subj-class: Statistical Mechanics; Superconductivity
\\ ( , 72kb)
Paper: cond-mat/0605085
replaced with revised version Thu, 13 Jul 2006 10:16:23 GMT (37kb)

Title: Finite temperature thermodynamics of two-component ultracold Fermi gas
Authors: Armen Sedrakian, Herbert M\"uther, Artur Polls
Comments: 4 pages, 3 figures. v2 includes a discussion of instabilities
Subj-class: Superconductivity; Statistical Mechanics
\\ ( , 37kb)
Paper: quant-ph/0607079
Date: Thu, 13 Jul 2006 08:14:20 GMT (130kb)

Title: Exact propagators for atom-laser interactions
Authors: A. del Campo, J. G. Muga
Comments: 13 pages, 6 figures
   A class of exact propagators describing the interaction of an $N$-level atom
with a set of on-resonance $\delta$-lasers is obtained by means of the Laplace
transform method. State-selective mirrors are described in the limit of strong
lasers. The ladder, V and $\Lambda$ configurations for a three-level atom are
discussed. For the two level case, the transient effects arising as result of
the interaction between both a semi-infinite beam and a wavepacket with the
on-resonance laser are examined.
\\ ( , 130kb)
Paper: cond-mat/0607358
Date: Fri, 14 Jul 2006 08:24:58 GMT (179kb)

Title: A Scanning Electron Microscope for Ultracold Atoms
Authors: T. Gericke, C. Utfeld, N. Hommerstad, H. Ott
Comments: 5 pages, 2 figures
Subj-class: Statistical Mechanics
Journal-ref: Laser Phys. Lett. 3, 415-419 (2006)
DOI: 10.1002/lapl.200610028
   We propose a new technique for the detection of single atoms in ultracold
quantum gases. The technique is based on scanning electron microscopy and
employs the electron impact ionization of trapped atoms with a focussed
electron probe. Subsequent detection of the resulting ions allows for the
reconstruction of the atoms position. This technique is expected to achieve a
much better spatial resolution compared to any optical detection method. In
combination with the sensitivity to single atoms, it makes new in situ
measurements of atomic correlations possible. The detection principle is also
well suited for the addressing of individual sites in optical lattices.
\\ ( , 179kb)
Paper: cond-mat/0607359
Date: Fri, 14 Jul 2006 08:32:13 GMT (287kb)

Title: Landau-Zener Tunnelling in a Nonlinear Three-level System
Authors: Guan-Fang Wang, Di-Fa Ye, Li-Bin Fu, Xu-Zong Chen, and Jie Liu
Comments: 8 pages, 8 figures
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We present a comprehensive analysis of the Landau-Zener tunnelling of a
nonlinear three-level system in a linearly sweeping external field. We find the
presence of nonzero tunnelling probability in the adiabatic limit (i.e., very
slowly sweeping field) even for the situation that the nonlinear term is very
small and the energy levels keep the same topological structure as that of
linear case. In particular, the tunnelling is irregular with showing an
unresolved sensitivity on the sweeping rate. For the case of fast-sweeping
fields, we derive an analytic expression for the tunnelling probability with
stationary phase approximation and show that the nonlinearity can dramatically
influence the tunnelling probability when the nonlinear "internal field"
resonate with the external field. We also discuss the asymmetry of the
tunnelling probability induced by the nonlinearity. Physics behind the above
phenomena is revealed and possible application of our model to triple-well
trapped Bose-Einstein condensate is discussed.
\\ ( , 287kb)
Paper: cond-mat/0607361
Date: Fri, 14 Jul 2006 09:00:23 GMT (73kb)

Title: Collective excitations of a Bose-Einstein condensate in an anharmonic
Authors: Guan-Qiang Li, Li-Bin Fu, Ju-Kui Xue, Xu-Zong Chen, and Jie Liu
Comments: 5 pages, 4 figures
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We investigate the collective excitations of a one-dimensional Bose-Einstein
condensate (BEC) with repulsive interaction between atoms in a quadratic plus
quartic trap. By using the variational approach, the coupled equations of
motion for the center-of-mass coordinate of the condensate and its width are
derived. Then, two low-energy excitation modes are obtained analytically. The
frequency shift induced by the anharmonic distortion, and the collapse and
revival of the collective excitations, which originate from the nonlinear
coupling between the two modes, are discussed.
\\ ( , 73kb)
Paper: cond-mat/0607371
Date: Fri, 14 Jul 2006 12:34:53 GMT (18kb)

Title: Quantum fluctuations and collective oscillations of a Bose-Einstein
   condensate in a 2D optical lattice
Authors: G. Orso, C. Menotti and S. Stringari
Comments: 5 pages, 3 figures
Subj-class: Other
   We use Bogoliubov theory to calculate the beyond mean field correction to the
equation of state of a weakly interacting Bose gas in the presence of a tight
2D optical lattice. We show that the lattice induces a characteristic 3D to 1D
crossover in the behaviour of quantum fluctuations. Using the hydrodynamic
theory of superfluids, we calculate the corresponding shift of the collective
frequencies of a harmonically trapped gas. We find that this correction can be
of the order of a few percent and hence easily measurable in current
experiments. The behavior of the quantum depletion of the condensate is also
\\ ( , 18kb)
Paper: cond-mat/0605138
replaced with revised version Fri, 14 Jul 2006 10:00:17 GMT (52kb)

Title: Landau functions for non-interacting bosons
Authors: Andreas Sinner, Florian Schuetz, and Peter Kopietz
Comments: 4 pages, 4 figures; final version to appear as a rapid communication
   in Physical Review A. Abstract modified and typos corrected
Subj-class: Statistical Mechanics
\\ ( , 52kb)
Paper: quant-ph/0607094
Date: Fri, 14 Jul 2006 12:16:57 GMT (14kb)

Title: Quantum simulations under translational symmetry
Authors: Christina V. Kraus, Michael M. Wolf, J. Ignacio Cirac
Comments: 8 pages
   We investigate the power of quantum systems for the simulation of Hamiltonian
time evolutions on a cubic lattice under the constraint of translational
invariance. Given a set of translationally invariant local Hamiltonians and
short range interactions we determine time evolutions which can and those that
can not be simulated. Whereas for general spin systems no finite universal set
of generating interactions is shown to exist, universality turns out to be
generic for quadratic bosonic and fermionic nearest-neighbor interactions when
supplemented by all translationally invariant on-site Hamiltonians.
\\ ( , 14kb)
Paper: quant-ph/0607098
Date: Fri, 14 Jul 2006 14:43:47 GMT (30kb)

Title: How to measure the wave-function absolute squared of a moving particle:
   do it with mirrors
Authors: Volker Hannstein Gerhard C. Hegerfeldt
Comments: 4 pages, 4 figures
   We consider a slow particle with wave function $\psi_t(\vec{x})$, moving
freely in some direction. A mirror is briefly switched on around a time $T$ and
its position is scanned. It is shown that the measured reflection probability
then allows the determination of $|\psi_T(\vec{x})|^2$. Experimentally
available atomic mirrors should make this method applicable to the
center-of-mass wave function of atoms with velocities in the cm/s range.
\\ ( , 30kb)
Paper: physics/0607140
Date: Fri, 14 Jul 2006 14:52:21 GMT (516kb)

Title: Effective-range description of a Bose gas under strong one- or
   two-dimensional confinement
Authors: Pascal Naidon, Eite Tiesinga, William F. Mitchell, and Paul S.
Comments: 6 pages, 3 figures
Subj-class: Atomic Physics
   We point out that theories describing s-wave collisions of bosonic atoms
confined in one- or two-dimensional geometries can be extended to much tighter
confinements than previously thought. This is achieved by replacing the
scattering length by an energy-dependent scattering length which was already
introduced for the calculation of energy levels under 3D confinement. This
replacement accurately predicts the position of confinement-induced resonances
in strongly confined geometries.
\\ ( , 516kb)
Paper: cond-mat/0607397
Date: Sat, 15 Jul 2006 20:33:59 GMT (142kb)

Title: Heisenberg limited interferometry via a two-component Mott insulating to
   superfluid transition
Authors: M. Rodr\'iguez, S. R. Clark, and D. Jaksch
Comments: 4 pages, 4 figures
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We propose the dynamical creation of twin-Fock and macroscopic superposition
states, which both exhibit Heisenberg limited interferometric phase
sensitivities, in an optical lattice. In our scheme a two-component Mott
insulator with two bosonic atoms per lattice site is melted into a superfluid.
This process transforms local correlations between hyperfine states of atom
pairs into multi-particle correlations extending over the whole system. The
melting time does not scale with the system size which makes our scheme
experimentally feasible.
\\ ( , 142kb)
Paper: cond-mat/0607401
Date: Sun, 16 Jul 2006 15:25:19 GMT (16kb)

Title: Probing the Superfluid - Mott Insulating Shell Structure of Cold Atoms
   by Parametric Excitations
Authors: Lilach Goren, Eros Mariani and Ady Stern
Comments: 4 pages, 1 figure
Subj-class: Other
   We study the effect of parametric excitations on systems of confined
ultracold Bose atoms in periodically modulated optical lattices. In the regime
where Mott insulating and Superfluid domains coexist, we show that the
dependence of the energy absorbed by the system on the frequency of the
modulation serves as an experimental probe for the existence and properties of
Mott insulating-Superfluid domains.
\\ ( , 16kb)
Paper: cond-mat/0607405
Date: Mon, 17 Jul 2006 08:16:26 GMT (434kb)

Title: Density fingerprint of giant vortices in Fermi gases near a Feshbach
Authors: Hui Hu and Xia-Ji Liu
Comments: 4 pages and 5 figures
Subj-class: Superconductivity; Strongly Correlated Electrons
   The structure of multiply quantized or giant vortex states in atomic Fermi
gases across a Feshbach resonance is studied within the context of
self-consistent Bogoliubov-de Gennes theory. The particle density profile of
vortices with $\kappa>1$ flux quanta is calculated. Owing to $\kappa$ discrete
branches of vortex core bound states, inside the core the density oscillates as
a function of the distance from the vortex line and displays a non-monotoic
dependence on the interaction strengths, in marked contrast to the singly
quantized case, in which the density depletes monotonically. This feature,
never reported so far, can make a direct visualization of the giant vortices in
atomic Fermi gases.
\\ ( , 434kb)
Paper: cond-mat/0607412
Date: Mon, 17 Jul 2006 10:58:17 GMT (5kb)

Title: Bose-Einstein Condensation and Casimir Force of Trapped Bose Gas to Slabs
Authors: Shyamal Biswas
Comments: 3 pages
Subj-class: Statistical Mechanics

For Bose gas in 3-d box with slab geometry it has been shown that at and below
the condensation temperature thermodynamic Casimir force appears (Martin and
Zagrebnov $[Europhys. Lett.,{\bf73} (2006) 15]$). This Casimir force has a
classical expression which is independent of $\hbar$. At finite temperatures
this force for photons in between two plates also has the classical expression
independent of $\hbar$. We study the Bose-Einstein Condensation for a 3-d system
of Bose gas which is harmonically trapped along two perpendicular directions and
is confined in between two slabs along the other perpendicular direction. We
calculate the Casimir force between the two slabs for this system of trapped
Bose gas. At finite temperatures the Casimir force for our system depends on

\\ ( , 5kb)
Paper: physics/0607149
Date: Mon, 17 Jul 2006 06:06:33 GMT (416kb)

Title: Multiple optical traps from a single laser beam using a mechanical
Authors: J.A. Dharmadhikari, A.K. Dharmadhikari, and D. Mathur
Comments: 8 pages, 3 figures, submitted to Applied Physics Letters in January
Subj-class: Optics; Biological Physics
   The use of a wire mesh facilitates creation of multiple optical traps for
manipulation of small micron or sub-micron particles. Such an array of optical
traps can be easily controlled. The trap that is formed in this manner is a
continuous trap; it obviates the need to time share a laser beam among a set of
positions, as is presently done in conventional multiple traps.
\\ ( , 416kb)
Paper: cond-mat/0607433
Date: Tue, 18 Jul 2006 02:03:45 GMT (45kb)

Title: Coherent Collective Excitations in a Superfluid: Broken Symmetries and
Authors: S.J. Han
Comments: 44 pages and 1 figure
Subj-class: Other
   We discuss the phase coherent collective excitations in both He II and atomic
Bose condensate. It is shown that a spontaneously broken gauge symmetry, which
always accompanies a longitudinal phonon (Nambu-Goldstone boson), takes place
at a nodal surface in a finite inhomogeneous Bose system. It is further shown
that the broken gauge symmetry is both a necessary and a sufficient condition
for the conservation of energy in an isolated system. We also give a detailed
discussion on the behavior of a surface layer of He II in which the two-fluid
model breaks down.
\\ ( , 45kb)
Paper: cond-mat/0607434
Date: Tue, 18 Jul 2006 02:36:31 GMT (245kb)

Title: Thermal dissipation in quantum turbulence
Authors: Michikazu Kobayashi and Makoto Tsubota
Comments: 4 pages, 6 figures, submitted to APS
Subj-class: Disordered Systems and Neural Networks; Statistical Mechanics
   The microscopic mechanism of thermal dissipation in quantum turbulence has
been numerically studied by solving the coupled system involving the
Gross-Pitaevskii equation and the Bogoliubov-de Gennes equation. At low
temperatures, the obtained dissipation does not work at scales greater than the
vortex core size. However, as the temperature increases, dissipation works at
large scales and it affects the vortex dynamics. We successfully obtained the
mutual friction coefficients of the vortex dynamics as functions of
temperature, which can be applied to the vortex dynamics in dilute
Bose-Einstein condensates.
\\ ( , 245kb)
Paper: cond-mat/0607438
Date: Tue, 18 Jul 2006 07:11:43 GMT (157kb)

Title: A Guided Quasicontinuous Atom Laser
Authors: William Guerin (LCFIO), Jean-F\'{e}lix Riou (LCFIO), John P. Gaebler
   (LCFIO), Vincent Josse (LCFIO), Philippe Bouyer (LCFIO), Alain Aspect (LCFIO)
Proxy: ccsd ccsd-00085308
Subj-class: Other
   We report the first realization of a guided quasicontinuous atom laser by rf
outcoupling a BEC from a hybrid optomagnetic trap into a horizontal atomic
waveguide. This configuration allows us to cancel the acceleration due to
gravity and thus to keep the de Broglie wavelength constant at a value of about
0.5 $\mu$m during 0.1 s of propagation. We also show that our configuration,
equivalent to pigtailing an optical fiber to a (photon) semiconductor laser,
ensures an intrinsically good transverse mode matching.
\\ ( , 157kb)
Paper: cond-mat/0607453
Date: Tue, 18 Jul 2006 17:52:16 GMT (47kb)

Title: Orthogonality catastrophe and shock waves in a non-equilibrium Fermi gas
Authors: E. Bettelheim, A. G. Abanov, and P. Wiegmann
Comments: 5 pages, 1 figure, revtex4, prl
Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall
   A semiclassical wave-packet propagating in a dissipationless Fermi gas
inevitably enters a "gradient catastrophe" regime, where an initially smooth
front develops large gradients and undergoes a dramatic shock wave phenomenon.
The non-linear effects in electronic transport are due to the curvature of the
electronic spectrum at the Fermi surface. They can be probed by a sudden
switching of a local potential. In equilibrium, this process produces a large
number of particle-hole pairs, a phenomenon closely related to the
Orthogonality Catastrophe. We study a generalization of this phenomenon to the
non-equilibrium regime and show how the Orthogonality Catastrophe cures the
Gradient Catastrophe, providing a dispersive regularization mechanism. We show
that a wave packet overturns and collapses into modulated oscillations with the
wave vector determined by the height of the initial wave. The oscillations
occupy a growing region extending forward with velocity proportional to the
initial height of the packet. We derive a fundamental equation for the
transition rates (MKP-equation) and solve it by means of the Whitham modulation
\\ ( , 47kb)
Paper: cond-mat/0507586
replaced with revised version Tue, 18 Jul 2006 11:56:21 GMT (73kb)

Title: Phase diagram of a cold polarized Fermi gas
Authors: D.T.Son, M.A.Stephanov
Comments: 6 pages, 5 figures; added an Appendix on the global stability of the
   splitting point
Report-no: INT-PUB 05-18
Subj-class: Other
Journal-ref: Phys.Rev. A74 (2006) 013614
DOI: 10.1103/PhysRevA.74.013614
\\ ( , 73kb)
Paper: cond-mat/0607253
replaced with revised version Tue, 18 Jul 2006 15:26:21 GMT (45kb)

Title: Classifying Novel Phases of Spinor Atoms
Authors: Ryan Barnett, Ari Turner, Eugene Demler
Comments: Added references
Subj-class: Strongly Correlated Electrons
\\ ( , 45kb)
Paper: quant-ph/0607121
Date: Tue, 18 Jul 2006 10:21:58 GMT (128kb)

Title: Scattering of two-level atoms by delta lasers: Exactly solvable models
   in atom optics
Authors: D. Seidel, J.G. Muga, G.C. Hegerfeldt
Comments: 11 pages, 5 figures
   We study the scattering of two-level atoms at narrow laser fields, modeled by
a $\delta$-shape intensity profile. The unique properties of these potentials
allow us to give simple analytic solutions for one or two field zones. Several
applications are studied: a single $\delta$-laser may serve as a detector model
for atom detection and arrival-time measurements, either by means of
fluorescence or variations in occupation probabilities. We show that, in
principle, this ideal detector can measure the particle density, the quantum
mechanical flux, arrival time distributions or local kinetic energy densities.
Moreover, two spatially separated $\delta$-lasers are used to investigate
quantized-motion effects on Ramsey interferometry.
\\ ( , 128kb)
Paper: quant-ph/0605245
replaced with revised version Tue, 18 Jul 2006 13:57:35 GMT (66kb)

Title: Manipulating Single Neutral Atoms in Optical Lattices
Authors: Chuanwei Zhang, S. L. Rolston, and S. Das Sarma
Comments: 5 pages, 3 figures, a typos for the focused laser intensity pattern
   is corrected. No results change
Subj-class: Quantum Physics; Soft Condensed Matter
\\ ( , 66kb)
Paper: cond-mat/0607459
Date: Tue, 18 Jul 2006 21:55:44 GMT (257kb)

Title: Superfluidity in Three-species Mixture of Lithium Gases across Feshbach
Authors: Hui Zhai
Comments: 4 pages, 3 figures
Subj-class: Superconductivity
   In this letter we study the phase diagram and the properties of the
superfluid phase in a mixture of the lowest three hyperfine spin states of
lithium, within a particular range of magnetic field where two Feshbach
resonances are close to each other. In the BEC side of two resonances the
system is a binary mixture of molecular condensates, which undergoes a
crossover to a superfluid containing two kinds of Cooper pairs as approaching
resonances. Some remarkable properties, as well as the experimental
consequences, of this superfluid phase are discussed. A quantum phase
transition to the normal state is predicted at the BCS sides of two resonances,
and the phase separation instability is also discussed.
\\ ( , 257kb)
Paper: cond-mat/0607463
Date: Wed, 19 Jul 2006 00:32:08 GMT (14kb)

Title: Quantum insulating states of F=2 cold atoms in optical lattices
Authors: Fei Zhou and Gordon W. Semenoff (PITP and UBC)
Comments: 4 pages, 1 figure included
Subj-class: Other
   In this Letter we study various spin correlated insulating states of F=2 cold
atoms in optical lattices. We find that the effective spin exchange interaction
due to virtual hopping contains an {\em octopole} coupling between two
neighboring lattice sites. Depending on scattering lengths and numbers of
particles per site the ground states are either rotationally invariant dimer or
trimer Mott insulators or insulating states with various spin orders. Three
spin ordered insulating phases are ferromagnetic, cyclic and nematic Mott
insulators. We estimate the phase boundaries for states with different numbers
of atoms per lattice site.
\\ ( , 14kb)
Paper: cond-mat/0607464
Date: Wed, 19 Jul 2006 01:19:23 GMT (297kb)

Title: States of fermionic atoms in an optical superlattice across a Feshbach
Authors: T. Goodman and L.-M. Duan
Comments: 10 pages, 11 figures
Subj-class: Other
   We investigate states of fermionic atoms across a broad Feshbach resonance in
an optical superlattice which allows interaction only among a small number of
lattice sites. The states are in general described by superpositions of atomic
resonating valence bonds and dressed molecules. As one scans the magnetic
field, level crossing is found between states with different symmetry
properties, which may correspond to a quantum phase transition in the many-body
\\ ( , 297kb)
Paper: cond-mat/0607465
Date: Wed, 19 Jul 2006 01:42:36 GMT (181kb)

Title: Modulated Bose-Einstein Condensate in BaCuSi2O6
Authors: Ch. R\"uegg, D.F. McMorrow, B. Normand, H.M. Ronnow, S.E. Sebastian,
   I.R. Fisher, C.D. Batista, S. Gvasaliya, Ch. Niedermayer, J. Stahn
Comments: 5 pages, 4 figures
Subj-class: Strongly Correlated Electrons
   The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S
= 1/2 moments on a quasi-2D square lattice. We have investigated its spin
dynamics by inelastic neutron scattering experiments on single crystals with an
energy resolution considerably higher than in an earlier study. We observe
multiple magnon modes, indicating clearly that the magnetic Hamiltonian is more
complex than previously understood. Inequivalent dimer sites lead to a distinct
form of magnon Bose-Einstein condensate (BEC) with a spatially modulated
condensate amplitude.
\\ ( , 181kb)
Paper: cond-mat/0607476
Date: Wed, 19 Jul 2006 08:35:00 GMT (16kb)

Title: Co-existence and shell structures of several superfluids in trapped
   three-component Fermi mixtures
Authors: T. Paananen, P. Torma, and J.-P. Martikainen
Comments: 4 pages, 4 figures
Subj-class: Superconductivity
   We study the properties of a trapped interacting three component Fermi gas.
We assume that one of the components can have a different mass from the other
two. We calculate the different phases of the three component mixture and find
a rich variety of different phases corresponding to different pairing channels,
and simple ways of tuning the system from one phase to another. In particular,
we predict co-existence of several different superfluids in the trap, forming a
shell structure, and phase transitions from this mixture of superfluids to a
single superfluid when the system parameters or temperature is varied. Such
shell structures realize superfluids with a non-trivial spatial topology and
leave clear observable signatures in the density profile of the gas.
\\ ( , 16kb)
Paper: cond-mat/0607490
Date: Wed, 19 Jul 2006 14:17:46 GMT (23kb)

Title: Time-dependent multi-orbital mean-field for fragmented Bose-Einstein
Authors: O. E. Alon, A. I. Streltsov, and L. S. Cederbaum
Comments: 16 pages, 1 figure
Subj-class: Other
   The evolution of Bose-Einstein condensates is usually described by the famous
time-dependent Gross-Pitaevskii equation, which assumes all bosons to reside in
a single time-dependent orbital. In the present work we address the evolution
of fragmented condensates, for which two (or more) orbitals are occupied, and
derive a corresponding time-dependent multi-orbital mean-field theory. We call
our theory TDMF($n$), where $n$ stands for the number of evolving fragments.
Working equations for a general two-body interaction between the bosons are
explicitly presented along with an illustrative numerical example.
\\ ( , 23kb)
Paper: cond-mat/0607491
Date: Wed, 19 Jul 2006 14:30:04 GMT (142kb)

Title: Collective modes as a probe of the equation of state for partially
   polarized Fermi gases
Authors: Theja N. De Silva, Erich J. Mueller
Comments: 4 pages, 2 figures
Subj-class: Other
   We calculate the collective modes of a partially polarized Fermi gas trapped
in a spherically symmetric harmonic potential. We show that the breathing mode
frequency exhibits non-monotonic dependence on polarization in the entire
BCS-BEC crossover region. Moreover, we find that the breathing mode can be used
to distinguish between two commonly used unitary gas equations of state.
\\ ( , 142kb)
Paper: cond-mat/0607493
Date: Wed, 19 Jul 2006 15:00:53 GMT (162kb)

Title: Collective mode of homogeneous superfluid Fermi gases in the BEC-BCS
Authors: R. Combescot, M.Yu. Kagan and S. Stringari
Comments: 21 pages
Subj-class: Other
   We perform a detailed study of the collective mode across the whole BEC-BCS
crossover in fermionic gases at zero temperature, covering the whole range of
energy beyond the linear regime. This is done on the basis of the dynamical BCS
model. We recover first the results of the linear regime in a simple form. Then
specific attention is payed to the non linear part of the dispersion relation
and its interplay with the continuum of single fermionic excitations. In
particular we consider in detail the merging of collective mode into the
continuum of single fermionic excitations. This occurs not only on the BCS side
of the crossover, but also slightly beyond unitarity on the BEC side. Another
remarkable feature is the very linear behaviour of the dispersion relation in
the vicinity of unitarity almost up to merging with the continuum. Finally,
while on the BEC side the mode is quite analogous to the Bogoliubov mode, a
difference appear at high wavevectors. On the basis of our results we determine
the Landau critical velocity in the BEC-BCS crossover which is found to be
largest close to unitarity. Our investigation has revealed interesting
qualitative features which would deserve experimental exploration as well as
further theoretical studies by more sophisticated means.
\\ ( , 162kb)
Paper: cond-mat/0512628
replaced with revised version Wed, 19 Jul 2006 18:45:49 GMT (84kb)

Title: Effective field theory of boson-fermion mixtures and bound fermion
   states on a vortex of boson superfluid
Authors: Yusuke Nishida and Dam Thanh Son
Comments: 14 pages, 4 figures, revtex4; typos corrected, references added,
   version to appear in Phys. Rev. A
Report-no: INT-PUB 05-31, TKYNT-05-31
Subj-class: Other
Journal-ref: Phys. Rev. A 74, 013615 (2006)
DOI: 10.1103/PhysRevA.74.013615
\\ ( , 84kb)
Paper: cond-mat/0603340
replaced with revised version Wed, 19 Jul 2006 08:10:21 GMT (25kb)

Title: Calogero-Sutherland gas of ultracold Bose atoms
Authors: Yue Yu
Comments: 4 pages,1 figure,update version
Subj-class: Other; Statistical Mechanics; Mathematical Physics
\\ ( , 25kb)
Paper: quant-ph/0607131
Date: Wed, 19 Jul 2006 19:03:59 GMT (290kb)

Title: Coherent acceleration of material wavepackets in modulated optical
Authors: Farhan Saif and Pierre Meystre
   We study the quantum dynamics of a material wavepacket bouncing off a
modulated atomic mirror in the presence of a gravitational field. We find the
occurrence of coherent accelerated dynamics for atoms beyond the familiar
regime of dynamical localization. The acceleration takes place for certain
initial phase space data and within specific windows of modulation strengths.
The realization of the proposed acceleration scheme is within the range of
present day experimental possibilities.
\\ ( , 290kb)
Paper: cond-mat/0607503
Date: Wed, 19 Jul 2006 20:59:12 GMT (21kb)

Title: Collective Excitations of a Two-Component Bose Condensate at Finite
Authors: C.-H. Zhang, H. A. Fertig
Comments: 4 pages, 3 figures, Submitted to PRL
Subj-class: Other
   We compare the collective modes for Bose-condensed systems with two
degenerate components with and without spontaneous intercomponent coherence at
finite temperature using the time-dependent Hartree-Fock approximation. We show
that the interaction between the condensate and non-condensate in these two
cases results in qualitatively different collective excitation spectra. We show
that at zero temperature the single-particle excitations of the incoherent Bose
condensate can be probed by intercomponent excitations.
\\ ( , 21kb)
Paper: cond-mat/0607519
Date: Thu, 20 Jul 2006 13:23:01 GMT (87kb)

Title: Energetics and structural properties of three-dimensional bosonic
   clusters near threshold
Authors: G. J. Hanna, and D. Blume
Comments: 12 pages, 12 figures
Subj-class: Other
   We treat three-dimensional bosonic clusters wih up to N=40 atoms, interacting
additively through two-body Van der Waals potentials, in the near-threshold
regime. Our study inludes super-borromean systems with N atoms for which all
subsystems are unbound. We determine the energetics and structural properties
as the expectation value of the interparticle distance as a function of the
coupling strength. It has been shown that the coupling strength g*(N), for
which the N-body systems becomes unbound, is bounded by the coupling constant
g*(N-1) for which the next smaller system with N-1 atoms becomes unbound, i.e.,
g*(N) >= (N-1)/Ng*(N-1). By fitting our numerically determined ground state
energies to a simple functional form with three fitting parameters, we
determine the relationship between g*(N) and g*(N-1). Our trimer and tetramer
energies fall on the so-called Tjon line, which has been studied in nuclear
physics. We confirm the existence of generalized Tjon lines for larger
clusters. Signatures of the universal behavior of weakly-bound
three-dimensional clusters can possibly be observed in ultracold Bose gases.
\\ ( , 87kb)
Paper: cond-mat/0603838
replaced with revised version Thu, 20 Jul 2006 01:17:03 GMT (634kb)

Title: Modulation instability and solitary wave formation in two-component
   Bose-Einstein condensates
Authors: Kenichi Kasamatsu, Makoto Tsubota
Comments: 15 pages, 10 figures
Subj-class: Other
Journal-ref: Phys. Rev. A 74, 013617 (2006)
\\ ( , 634kb)
Paper: cond-mat/0606319
replaced with revised version Thu, 20 Jul 2006 15:08:42 GMT (15kb)

Title: Off-diagonal correlations of lattice impenetrable bosons in one
Authors: D.M. Gangardt, G.V. Shlyapnikov
Comments: 10 pages. Submitted to the Focus Issue on 'Cold Atoms in Optical
   Lattices' of New Journal of Physics
Subj-class: Statistical Mechanics
\\ ( , 15kb)
Paper: physics/0607183
Date: Thu, 20 Jul 2006 18:19:17 GMT (23kb)

Title: Football: A Naive Approximation to the Effect of Increasing Goal Size on
   the Number of Goals
Authors: J. Mira
Comments: 4 pages
Subj-class: Physics and Society; Popular Physics
   The effect of increasing goal mouth size on the number of goals scored in a
football match is discussed in a very preliminary and simple way, considering
elastic collisions of the ball with the posts. The result is obtained on the
basis of data taken from the Spanish Professional League, that show a high
number of shots-to-post. Surprisingly, there is a direct correlation of the
increase in goal mouth area with the increase of goals.
Paper: cond-mat/0607542
Date: Fri, 21 Jul 2006 07:01:35 GMT (25kb)

Title: Analytic solution of the 1D finite coupling delta function Bose gas
Authors: P. J. Forrester, N. E. Frankel and M. I. Makin
Comments: 23 pages, 0 figures, uses rotate.sty
Subj-class: Statistical Mechanics
   An intensive study for both the weak coupling and strong coupling limits of
the ground state properties of this classic system is presented. Detailed
results for specific values of finite $N$ are given and from them results for
general $N$ are determined. We focus on the density matrix and concomitantly
its Fourier transform, the occupation numbers, along with the pair correlation
function and concomitantly its Fourier transform, the structure factor. These
are the signature quantities of the Bose gas. One specific result is that for
weak coupling a rational polynomial structure holds despite the transcendental
nature of the Bethe equations. All these new results are predicated on the
Bethe ansatz and are built upon the seminal works of the past.
\\ ( , 25kb)
Paper: cond-mat/0607546
Date: Fri, 21 Jul 2006 10:21:21 GMT (13kb)

Title: Bose Condensed Gas in Strong Disorder Potential With Arbitrary
   Correlation Length
Authors: Patrick Navez, Axel Pelster, Robert Graham
Comments: Author information under
Subj-class: Disordered Systems and Neural Networks
   We study the properties of a dilute Bose condensed gas at zero temperature in
the presence of a strong random potential with arbitrary correlation length.
Starting from the underlying Gross-Pitaevskii equation, we use the random phase
approximation in order to get a closed integral equation for the averaged
density distribution which allows to determine both the condensate and the
superfluid density. The obtained results generalize those of Huang and Meng
(HM) to strong disorder. In particular, we find the critical value of the
disorder strength, where the superfluid phase disappears by a first-order phase
transition. We show how this critical value changes as a function of the
correlation length.
\\ ( , 13kb)
Paper: cond-mat/0607556
Date: Fri, 21 Jul 2006 14:52:29 GMT (21kb)

Title: Interferences in the density of two initially independent Bose-Einstein
Authors: L. S. Cederbaum, A. I. Streltsov, Y. B. Band, and O. E. Alon
Comments: 13 pages, 2 figures
Subj-class: Other
   It is shown that the density of two {\it initially independent} condensates
which are allowed to expand and overlap can show interferences as a function of
time due to interparticle interaction. Using many-body theory, explicit
expressions for the density are given which are exact in the weak interaction
limit. General working equations are discussed which reproduce exactly the
density in this limit. Illustrative examples are presented.
\\ ( , 21kb)
Paper: cond-mat/0607558
Date: Fri, 21 Jul 2006 15:09:34 GMT (269kb)

Title: Quantum resonances and rectification of driven cold atoms in optical
Authors: S. Denisov, L. Morales-Molina, and S. Flach
Comments: 4 pages, 4 figures
Subj-class: Statistical Mechanics
   Classical Hamiltonian ratchets have been recently successfully realized using
cold atoms in driven optical lattices. Here we study the current rectification
of the motion of a quantum particle in a periodic potential exposed to an
external ac field. The dc current appears due to the desymmetrization of
Floquet eigenstates, which become transporting. Quantum dynamics enhances the
dependence of the current on the initial phase of the driving field. By
changing the laser field parameters which control the degree of space-time
asymmetry, Floquet eigenstates are tuned through avoided crossings. These
quantum resonances induce resonant changes of the resulting current. The width,
strength and position of these quantum resonances are tunable using control
parameters of the experimental realization with cold atoms.
\\ ( , 269kb)

Till next week,

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
Legal stuff: Unless stated otherwise, this e-mail represents only the
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Received on Tue Jul 25 2006 - 02:18:55 EST

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