Matt's arXiv selection, Friday 28 July 2006.

From: Matthew Davis <>
Date: Fri, 28 Jul 2006 19:48:42 +1000 (EST)

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

Hi all,

The arXiv mailings continue to be irregular due to my travels (this week I am at
Orsay). Two interesting looking papers on the formation of heteronuclear
molecules this week, one from Hamburg and one from Boulder.

Home page:

The abstracts:

Paper: cond-mat/0607569
Date: Fri, 21 Jul 2006 20:21:58 GMT (97kb)

Title: Nonuniform mixed-parity superfluid state in Fermi gases
Authors: K. V. Samokhin and M. S. Mar'enko
Comments: 4 pages, 1 figure
Subj-class: Superconductivity
   We study the effects of dipole interaction on the superfluidity in a
homogeneous Fermi gas with population imbalance. We show that the
Larkin-Ovchinnikov-Fulde-Ferrell phase is replaced by another nonuniform
superfluid phase, in which the order parameter has a nonzero triplet component
induced by the dipole interaction.
\\ ( , 97kb)
Paper: cond-mat/0607581
Date: Sun, 23 Jul 2006 01:18:57 GMT (261kb)

Title: Ultracold heteronuclear molecules in a 3D optical lattice
Authors: C. Ospelkaus, S. Ospelkaus, L. Humbert, P. Ernst, K. Sengstock, and K.
Comments: 4 pages, 4 figures
Subj-class: Statistical Mechanics
   We report on the creation of ultracold heteronuclear molecules assembled from
fermionic 40K and bosonic 87Rb atoms in a 3D optical lattice. Molecules are
produced at a heteronuclear Feshbach resonance both on the attractive and the
repulsive side of the resonance. We precisely determine the binding energy of
the heteronuclear molecules from rf spectroscopy across the Feshbach resonance.
We characterize the lifetime of the molecular sample as a function of magnetic
field and measure between 20 and 120ms. The efficiency of molecule creation via
rf association is measured and is found to decrease as expected for more deeply
bound molecules.
\\ ( , 261kb)
Paper: cond-mat/0607600
Date: Mon, 24 Jul 2006 16:06:57 GMT (34kb)

Title: Analytic, Group-Theoretic Density Profiles for Confined, Correlated
   N-Body Systems
Authors: W.B. Laing, M. Dunn, D.K. Watson
Comments: 15 pages, 2 figures, submitted to Physics Review A
Subj-class: Other
   Confined quantum systems involving $N$ identical interacting particles are to
be found in many areas of physics, including condensed matter, atomic and
chemical physics. A beyond-mean-field perturbation method that is applicable,
in principle, to weakly, intermediate, and strongly-interacting systems has
been set forth by the authors in a previous series of papers. Dimensional
perturbation theory was used, and in conjunction with group theory, an analytic
beyond-mean-field correlated wave function at lowest order for a system under
spherical confinement with a general two-body interaction was derived. In the
present paper, we use this analytic wave function to derive the corresponding
lowest-order, analytic density profile and apply it to the example of a
Bose-Einstein condensate.
\\ ( , 34kb)
Paper: cond-mat/0607618
Date: Mon, 24 Jul 2006 15:58:15 GMT (62kb)

Title: Single-particle versus pair condensation of hard-core bosons with
   correlated hopping
Authors: K.P. Schmidt, J. Dorier, A. Laeuchli, and F. Mila
Comments: 8 pages, 7 figures
Subj-class: Other
   We investigate the consequences of correlated hopping on the ground state
properties of hard-core bosons on a square lattice as revealed by extensive
exact diagonalizations and quantum Monte Carlo simulations. While for non
interacting hard-core bosons the effective attraction induced by the correlated
hopping leads to phase separation at low density, we show that a modest
nearest-neighbor repulsion suppresses phase separation, leading to a remarkable
low-density pairing phase with no single particle Bose-Einstein condensation
but long-range two-particle correlations, signaling a condensation of pairs. We
also explain why the unusual properties of the pairing phase are a real
challenge for standard one-worm quantum Monte Carlo simulations.
\\ ( , 62kb)
Paper: cond-mat/0607619
Date: Mon, 24 Jul 2006 16:05:01 GMT (15kb)

Title: Manipulating Bose-Einstein condensed atoms in toroidal traps
Authors: A. D. Jackson (1), G. M. Kavoulakis (2) ((1) Niels Bohr Institute, (2)
   LTH, Lund)
Comments: 4 pages, RevTex, 2 figures
Subj-class: Other
   We consider Bose-Einstein condensed atoms confined in a toroidal trap. We
demonstrate that under conditions of one-dimensional behavior, the density
distribution of the atoms may be exponentially localized/delocalized, even for
very small variations in the trapping potential along the torus. This
observation allows one to control the atom density externally via slight
modifications of the trapping potential. For similar reasons, small
irregularities of the trap may also have a very pronounced effect on the
density of the cloud.
\\ ( , 15kb)
Paper: cond-mat/0604580
replaced with revised version Sun, 23 Jul 2006 11:08:06 GMT (16kb)

Title: Superfluidity in a Three-flavor Fermi Gas with SU(3) Symmetry
Authors: Lianyi He, Meng Jin and Pengfei Zhuang
Comments: Version accepted for publication in PRA
Subj-class: Other; Superconductivity; Atomic Physics
\\ ( , 16kb)
Paper: cond-mat/0605005
replaced with revised version Sat, 22 Jul 2006 01:08:04 GMT (50kb)

Title: Phase Transition in Imbalanced Fermion Superfluids
Authors: Heron Caldas
Comments: This is an invited contribution to a book titled "Pairing beyond BCS
   Theory in Fermionic Systems" (Mark Alford, John Clark and Armen Sedrakian,
   eds.), to be published by World Scientific. 3 figures, 12 pages. V4: Minor
Subj-class: Superconductivity; Strongly Correlated Electrons
\\ ( , 50kb)
Paper: quant-ph/0607165
Date: Mon, 24 Jul 2006 14:06:18 GMT (12kb)

Title: Models of measurement for quantum fields and for classical continuous
   random fields
Authors: Peter Morgan
Comments: This is a submission for the Proceedings of the Vaxjo Conference on
   the Foundations of Probability and Physics-4. Comments very welcome
   A quantum field model for an experiment describes thermal fluctuations
explicitly and quantum fluctuations implicitly, whereas a comparable continuous
random field model would describe both thermal and quantum fluctuations
explicitly. An ideal classical measurement does not affect the results of later
measurements, in contrast to ideal quantum measurements, but we can describe
the consequences of the thermal and quantum fluctuations of classically
non-ideal measurement apparatuses explicitly. Some details of continuous random
fields and of Bell inequalities for random fields will be discussed.
\\ ( , 12kb)
Paper: quant-ph/0603156
replaced with revised version Mon, 24 Jul 2006 05:43:46 GMT (21kb)

Title: Implementing 1 Dimensional Quantum (Hadamard) Walk using Bose-Einstein
Authors: C.M. Chandrashekar
Comments: 7 pages, 3 figures
\\ ( , 21kb)
Paper: physics/0607215
Date: Mon, 24 Jul 2006 19:55:59 GMT (149kb)

Title: Suppression of Reabsorption via Modulation of Light
Authors: Anthony R. Gorges, Ansel J. Foxley, David M. French, Christopher M.
   Ryan, and Jacob L. Roberts
Comments: 5 pages, 4 figures
Subj-class: Atomic Physics
   Reabsorption, the multiple scattering of spontaneously emitted photons in
optically thick gases, is a major limitation to efficient optical pumping and
laser cooling in ultracold gases. We report mitigation of reabsorption using
spatial and frequency modulation of laser light illuminating such gases. We
developed a semi-classical model that successfully describes the reabsorption
process when frequency-modulated light is present. It was necessary to extend
the treatment in the model beyond a simple two-atom picture in order to
reproduce our experimental results.
\\ ( , 124kb)
Paper: cond-mat/0607630
Date: Tue, 25 Jul 2006 08:11:53 GMT (824kb)

Title: Effect of Quadratic Zeeman Energy on the Vortex of Spinor Bose-Einstein
Authors: Tomoya Isoshima and Sungkit Yip
Comments: 6 pages, 5 figures. Published in J. Phys. Soc. Jpn
Subj-class: Other
Journal-ref: J. Phys. Soc. Jpn. 75, 074605 (2006)
DOI: 10.1143/JPSJ.75.074605
   The spinor Bose-Einstein condensate of atomic gases has been experimentally
realized by a number of groups. Further, theoretical proposals of the possible
vortex states have been sugessted. This paper studies the effects of the
quadratic Zeeman energy on the vortex states. This energy was ignored in
previous theoretical studies, although it exists in experimental systems. We
present phase diagrams of various vortex states taking into account the
quadratic Zeeman energy. The vortex states are calculated by the
Gross-Pitaevskii equations. Several new kinds of vortex states are found. It is
also found that the quadratic Zeeman energy affects the direction of total
magnetization and causes a significant change in the phase diagrams.
\\ ( , 824kb)
Paper: cond-mat/0603571
replaced with revised version Tue, 25 Jul 2006 08:50:34 GMT (406kb)

Title: Identifying the Bose glass phase
Authors: R. Pugatch, N. Bar-gill, N. Katz, E. Rowen, N. Davidson
Comments: 8 pages, 7 figures (expanded version)
Subj-class: Soft Condensed Matter; Other
\\ ( , 406kb)
Paper: quant-ph/0607171
Date: Tue, 25 Jul 2006 17:03:05 GMT (622kb)

Title: Quantized Rotation of Atoms From Photons with Orbital Angular Momentum
Authors: M. F. Andersen, C. Ryu, Pierre Clade, V. Natarajan, A. Vaziri, K.
   Helmerson, W. D. Phillips
Comments: 5 pages, 4 figures
   We demonstrate the coherent transfer of the orbital angular momentum of a
photon to an atom in quantized units of hbar, using a 2-photon stimulated Raman
process with Laguerre-Gaussian beams to generate an atomic vortex state in a
Bose-Einstein condensate of sodium atoms. We show that the process is coherent
by creating superpositions of different vortex states, where the relative phase
between the states is determined by the relative phases of the optical fields.
Furthermore, we create vortices of charge 2 by transferring to each atom the
orbital angular momentum of two photons.
\\ ( , 622kb)
Paper: physics/0607223
Date: Tue, 25 Jul 2006 11:31:17 GMT (619kb)

Title: Real Time Relativity
Authors: C. M. Savage, A. C. Searle, L. McCalman
Subj-class: Physics Education; Computational Physics
   Real Time Relativity is a computer program that allows the user to fly
through a virtual world governed by relativistic physics. The user controls a
'rocket' carrying a 'camera'. The rocket may be accelerated and steered, and
the camera may be pointed in any direction. It takes advantage of the fact that
video cards provide inexpensive data-parallel processing and are designed to
perform rapid arithmetic on four-dimensional vectors.
\\ ( , 619kb)
Paper: physics/0607224
Date: Tue, 25 Jul 2006 15:49:07 GMT (319kb)

Title: Scaling the h-index for different scientific ISI fields
Authors: Juan E. Iglesias and Carlos Pecharroman
Subj-class: Physics and Society
   We propose a simple way to put in a common scale the h values of researchers
working in different scientific ISI fields, so that the previsible misuse of
this index for inter-areas comparison might be prevented, or at least,
\\ ( , 319kb)
Paper: cond-mat/0607664
Date: Wed, 26 Jul 2006 15:18:00 GMT (302kb)

Title: Superfluid shells for trapped fermions with mass and population
Authors: G.-D. Lin, W. Yi and L.-M. Duan
Comments: 4 pages, 3 figures
Subj-class: Other
   We map out the phase diagram of strongly interacting fermions in a potential
trap with mass and population imbalance between the two spin components. As a
unique feature distinctively different from the equal-mass case, we show that
the superfluid here forms a shell structure which is not simply connected in
space. Different types of normal states occupy the trap regions inside and
outside this superfluid shell. We calculate the atomic density profiles, which
provide an experimental signature for the superfluid shell structure.
\\ ( , 302kb)
Paper: cond-mat/0607667
Date: Wed, 26 Jul 2006 19:18:22 GMT (106kb)

Title: Observation of Heteronuclear Feshbach Molecules from a $^{85}$Rb -
   $^{87}$Rb gas
Authors: S. B. Papp and C. E. Wieman
Subj-class: Other
   We report on the observation of ultracold heteronuclear Feshbach molecules.
Starting with a $^{87}$Rb BEC and a cold atomic gas of $^{85}$Rb, we utilize
previously unobserved interspecies Feshbach resonances to create up to 25,000
molecules. Even though the $^{85}$Rb gas is non-degenerate we observe a large
molecular conversion efficiency due to the presence of a quantum degenerate
$^{87}$Rb gas; this represents a key feature of our system. We compare the
molecule creation at two different Feshbach resonances with different
magnetic-field widths. The two Feshbach resonances are located at
$265.44\pm0.15$ G and $372.4\pm1.3$ G. We also directly measure the small
binding energy of the molecules through resonant magnetic-field association.
\\ ( , 106kb)
Paper: cond-mat/0607692
Date: Wed, 26 Jul 2006 15:03:43 GMT (16kb)

Title: Competing Compressible and Incompressible Phases in Rotating Atomic Bose
   Gases at Filling Factor $\nu=2$
Authors: N. R. Cooper and E. H. Rezayi
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We study the groundstates of weakly interacting atomic Bose gases under
conditions of rapid rotation. We present the results of large-scale exact
diagonalisation studies on a periodic geometry (a torus) which allows studies
of compressible states with broken translational symmetry. Focusing on filling
factor $\nu=2$, we show a competition between the triangular vortex lattice, a
quantum smectic state, and the incompressible $k=4$ Read-Rezayi state. We
discuss the corrections arising from finite size effects, and the likely
behaviour for large system sizes. The Read-Rezayi state is stabilised by a
moderate amount of additional dipolar interactions.
\\ ( , 16kb)
Paper: cond-mat/0607697
Date: Wed, 26 Jul 2006 17:21:51 GMT (570kb)

Title: Observation of Vortex Pinning in Bose-Einstein Condensates
Authors: S. Tung, V. Schweikhard, E. A. Cornell
Comments: 4 pages, 6 figures
Subj-class: Other
   We report the observation of vortex pinning in rotating gaseous Bose-Einstein
condensates (BEC). The vortices are pinned to columnar pinning sites created by
a co-rotating optical lattice superimposed on the rotating BEC. We study the
effects of two different types of optical lattice, triangular and square. With
both geometries we see an orientation locking between the vortex and the
optical lattices. At sufficient intensity the square optical lattice induces a
structural cross-over in the vortex lattice.
\\ ( , 570kb)
Paper (*cross-listing*): nucl-th/0607028
Date: Sat, 15 Jul 2006 09:35:37 GMT (615kb)

Title: Nuclear Superconductivity in Compact Stars: BCS Theory and Beyond
Authors: Armen Sedrakian, John W. Clark
Comments: 41 pages, 16 figures. Chapter contributed to "Pairing in Fermionic
   Systems: Basic Concepts and Modern Applications", World Scientific
Subj-class: Nuclear Theory; Superconductivity
   This chapter provides a review of microscopic theories of pairing in nuclear
systems and neutron stars. Special attention is given to the mean-field BCS
theory and its extensions to include effects of polarization of the medium and
retardation of the interactions. Superfluidity in nuclear systems that exhibit
isospin asymmetry is studied. We further address the crossover from the
weak-coupling BCS description to the strong-coupling BEC limit in dilute
nuclear systems. Finally, within the observational context of rotational
anomalies of pulsars, we discuss models of the vortex state in superfluid
neutron stars and of the mutual friction between superfluid and normal
components, along with the possibility of type-I superconductivity of the
proton subsystem.
\\ ( , 615kb)
Paper: cond-mat/0607253
replaced with revised version Wed, 26 Jul 2006 17:53:28 GMT (45kb)

Title: Classifying Novel Phases of Spinor Atoms
Authors: Ryan Barnett, Ari Turner, Eugene Demler
Comments: Added references, corrected typos, minor changes in text
Subj-class: Strongly Correlated Electrons
\\ ( , 45kb)
Paper: quant-ph/0607178
Date: Tue, 25 Jul 2006 20:21:40 GMT (781kb)

Title: Electrical detection of 31P spin quantum states
Authors: A. R. Stegner, C. Boehme, H. Huebl, M. Stutzmann, K. Lips and M. S.
   In recent years, a variety of solid-state qubits has been realized, including
quantum dots, superconducting tunnel junctions and point defects. Due to its
potential compatibility with existing microelectronics, the proposal by Kane
based on phosphorus donors in Si has also been pursued intensively. A key issue
of this concept is the readout of the P quantum state. While electrical
measurements of magnetic resonance have been performed on single spins, the
statistical nature of these experiments based on random telegraph noise
measurements has impeded the readout of single spin states. In this letter, we
demonstrate the measurement of the spin state of P donor electrons in silicon
and the observation of Rabi flops by purely electric means, accomplished by
coherent manipulation of spin-dependent charge carrier recombination between
the P donor and paramagnetic localized states at the Si/SiO2 interface via
pulsed electrically detected magnetic resonance. The electron spin information
is shown to be coupled through the hyperfine interaction with the P nucleus,
which demonstrates the feasibility of a recombination-based readout of nuclear
\\ ( , 781kb)
Paper: quant-ph/0607182
Date: Wed, 26 Jul 2006 14:29:14 GMT (201kb)

Title: Free-Space distribution of entanglement and single photons over 144 km
Authors: R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T.
   Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P.
   Trojek, B. Oemer, M. Fuerst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri,
   H. Weinfurter, A. Zeilinger
Comments: 10 pages including 2 figures and 1 table
   Quantum Entanglement is the essence of quantum physics and inspires
fundamental questions about the principles of nature. Moreover it is also the
basis for emerging technologies of quantum information processing such as
quantum cryptography, quantum teleportation and quantum computation. Bell's
discovery, that correlations measured on entangled quantum systems are at
variance with a local realistic picture led to a flurry of experiments
confirming the quantum predictions. However, it is still experimentally
undecided whether quantum entanglement can survive global distances, as
predicted by quantum theory. Here we report the violation of the
Clauser-Horne-Shimony-Holt (CHSH) inequality measured by two observers
separated by 144 km between the Canary Islands of La Palma and Tenerife via an
optical free-space link using the Optical Ground Station (OGS) of the European
Space Agency (ESA). Furthermore we used the entangled pairs to generate a
quantum cryptographic key under experimental conditions and constraints
characteristic for a Space-to-ground experiment. The distance in our experiment
exceeds all previous free-space experiments by more than one order of magnitude
and exploits the limit for ground-based free-space communication; significantly
longer distances can only be reached using air- or space-based platforms. The
range achieved thereby demonstrates the feasibility of quantum communication in
space, involving satellites or the International Space Station (ISS).
\\ ( , 201kb)
Paper: physics/0607234
Date: Wed, 26 Jul 2006 11:19:47 GMT (964kb)

Title: Molecule formation in ultracold atomic gases
Authors: Jeremy M. Hutson and Pavel Soldan
Comments: To be published in International reviews in Physical Chemistry, Vol.
   25, issue 4 (October 2006)
Subj-class: Chemical Physics; Atomic Physics
   This review describes recent experimental and theoretical advances in forming
molecules in ultracold gases of trapped alkali metal atoms, both by magnetic
tuning through Feshbach resonances and by photoassociation. Molecular
Bose-Einstein condensation of long-range states of both boson dimers and
fermion dimers was achieved in 2002-3. Condensates of boson dimers were found
to be short-lived, but long-lived condensates of fermion dimers have been
produced. Signatures of triatomic and tetraatomic molecules have recently been
observed. Both homonuclear and heteronuclear molecules have been formed by
photoassociation, mostly in very high vibrational levels. Recent attempts to
produce ultracold molecules in short-range states (low vibrational levels) are
described. Experimental and theoretical work on collisions of ultracold
molecules is discussed.
\\ ( , 964kb)
Paper: physics/0604079
replaced with revised version Tue, 25 Jul 2006 17:30:04 GMT (594kb)

Title: Magnetic trapping of buffer-gas cooled chromium atoms and prospects for
   the extension to paramagnetic molecules
Authors: Joost M. Bakker, Michael Stoll, Dennis R. Weise, Oliver Vogelsang,
   Gerard Meijer, and Achim Peters
Comments: 9 pages, 4 Figures. Accepted for J.Phys. B, special issue on cold
Subj-class: Atomic Physics
\\ ( , 594kb)
Paper: physics/0607034
replaced with revised version Wed, 26 Jul 2006 10:54:36 GMT (200kb)

Title: A Radio-Frequency Atom Chip for Trapping Atoms in Strong-field Seeking
Authors: Xiaolin Li, Haichao Zhang, Min Ke, Bo Yan, and Yuzhu Wang
Subj-class: Atomic Physics
\\ ( , 200kb)
Paper: cond-mat/0607704
Date: Wed, 26 Jul 2006 23:12:22 GMT (123kb)

Title: Radial and angular rotons in trapped dipolar gases
Authors: Shai Ronen, Daniele C. E. Bortolotti and John. L. Bohn
Comments: 4 pages, 3 figures
Subj-class: Statistical Mechanics
   We study Bose-Einstein condensates with purely dipolar interactions in oblate
(pancake) traps. We find that the condensate always becomes unstable to
collapse when the number of particles is sufficiently large. We analyze the
instability, and find that it is the trapped-gas analogue of the
``roton-maxon'' instability previously reported for a gas that is unconfined in
two dimensions. In addition, we find that under certain circumstances, the
condensate wave function attains a biconcave shape, with its maximum density
away from the center of the gas. These biconcave condensates become unstable
due to azimuthl excitation - an angular roton.
\\ ( , 123kb)
Paper: cond-mat/0607706
Date: Thu, 27 Jul 2006 00:47:38 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
   In the last several years considerable efforts have been devoted to
developing Bose-Einstein Condensate (BEC)-based devices for applications such
as fundamental research, precision measurements and integrated atom optics.
Such devices capable of complex functionality can be designed from simpler
building blocks as is done in microelectronics. One of the most important
components of microelectronics is a transistor. We demonstrate that
Bose-Einstein condensate in a three well potential structure where the
tunneling of atoms between two wells is controlled by the population in the
third, shows behavior similar to that of an electronic field effect transistor.
Namely, it exhibits switching and both absolute and differential gain. The role
of quantum fluctuations is analyzed, estimates of switching time and parameters
for the potential are presented.
\\ ( , 139kb)
Paper: cond-mat/0607711
Date: Thu, 27 Jul 2006 08:02:58 GMT (321kb)

Title: Magnon Bose condensation in symmetry breaking magnetic field
Authors: S. V. Maleyev, V. P. Plakhty, S. V. Grigoriev, A. I. Okorokov and A.
   V. Syromyatnikov
Comments: Submitted to J. of Phys. Condens. Matter (Proceedings of
   International Conference "Highly Frustrated Magnets", Osaka (Japan), August
   2006). 8 pages, 5 figures
Subj-class: Strongly Correlated Electrons
   Magnon Bose condensation (BC)in the symmetry breaking magnetic field is a
result of unusual form of the Zeeman energy, which has terms linear in the
spin-wave operators and terms mixing excitations differ in the Wave-vector of
the magnetic structure. The following examples are considered: simple
easy-plane tetragonal antiferromagnets (AF), frustrated AF family$R_2Cu O_4$
where $R=Pr,Nd$ etc. and cubic magnets with the Dzyaloshinskii-Moriya
interaction ($Mn Si$ etc.). In all cases the BC becomes important when the
magnetic field becomes comparable with the spin-wave gap. The theory is
illustrated by existing experimental results.
\\ ( , 321kb)
Paper: cond-mat/0607718
Date: Thu, 27 Jul 2006 12:25:37 GMT (792kb)

Title: Magnetism and Hund's Rule in an Optical Lattice with Cold Fermions
Authors: K. Karkkainen, M. Borgh, M. Manninen and S. M. Reimann
Comments: 5 pages, 4 figures
Subj-class: Other; Mesoscopic Systems and Quantum Hall Effect
   Artificially confined, small quantum systems show a high potential for
employing quantum physics in technology. Ultra-cold atom gases have opened an
exciting laboratory in which to explore many-particle systems that are not
accessible in conventional atomic or solid state physics. It appears promising
that optical trapping of cold bosonic or fermionic atoms will make construction
of devices with unprecedented precision possible in the future, thereby
allowing experimenters to make their samples much more "clean", and hence more
coherent. Trapped atomic quantum gases may thus provide an interesting
alternative to the quantum dot nanostructures produced today. Optical lattices
created by standing laser waves loaded with ultra-cold atoms are an example of
this. They provide a unique experimental setup to study artificial crystal
structures with tunable physical parameters. Here we demonstrate that a
two-dimensional optical lattice loaded with repulsive, contact-interacting
fermions shows a rich and systematic magnetic phase diagram. Trapping a few (N
=< 12) fermions in each of the single-site minima of the optical lattice, we
find that the em shell structure in these quantum wells determines the
magnetism. In a shallow lattice, the tunneling between the lattice sites is
strong, and the lattice is non-magnetic. For deeper lattices, however, the
shell-filling of the single wells with fermionic atoms determines the
magnetism. As a consequence of Hund's first rule, the interaction energy is
lowered by maximizing the number of atoms of the same species. This leads to a
systematic sequence of non-magnetic, ferromagnetic and antiferromagnetic
\\ ( , 792kb)
Paper: cond-mat/0607721
Date: Thu, 27 Jul 2006 13:05:09 GMT (65kb)

Title: Equation of state of an interacting Bose gas at finite temperature: a
   Path Integral Monte Carlo study
Authors: S. Pilati, K. Sakkos, J. Boronat, J. Casulleras and S. Giorgini
Comments: 7 pages, 6 figures
Subj-class: Other
   By using exact Path Integral Monte Carlo methods we calculate the equation of
state of an interacting Bose gas as a function of temperature both below and
above the superfluid transition. The universal character of the equation of
state for dilute systems and low temperatures is investigated by modeling the
interatomic interactions using different repulsive potentials corresponding to
the same s-wave scattering length. The results obtained for the energy and the
pressure are compared to the virial expansion for temperatures larger than the
critical temperature. At very low temperatures we find agreement with the
ground-state energy calculated using the diffusion Monte Carlo method.
\\ ( , 65kb)
Paper: cond-mat/0607722
Date: Thu, 27 Jul 2006 14:07:47 GMT (61kb)

Title: One-dimensional extended Bose-Hubbard model with a confining potential:
   a DMRG analysis
Authors: Laura Urba, Emil Lundh, Anders Rosengren
Comments: 14 pages, 11 figures
Subj-class: Strongly Correlated Electrons; Other
   The extended Bose-Hubbard model in a quadratic trap potential is studied
using a finite-size density-matrix renormalization group method (DMRG). We
compute the boson density profiles, the local compressibility and the hopping
correlation functions. We observed the phase separation induced by the trap in
all the quantities studied and conclude that the local density approximation is
valid in the extended Bose-Hubbard model. From the plateaus obtained in the
local compressibility it was possible to obtain the phase diagram of the
homogeneous system which is in agreement with previous results.
\\ ( , 61kb)
Paper: cond-mat/0607726
Date: Thu, 27 Jul 2006 15:10:48 GMT (223kb)

Title: An effective potential for one-dimensional matter-wave solitons in an
   axially inhomogeneous trap
Authors: Sergio De Nicola, Boris A. Malomed, Renato Fedele
Comments: to be published in Physics Letters A
Subj-class: Soft Condensed Matter
   We demonstrate that a tight transverse trap with the local frequency, $%
\omega_{\perp}$, gradually varying in the longitudinal direction ($x$) induces
an effective potential for one-dimensional solitons in a self-attractive
Bose-Einstein condensate. An analytical approximation for this potential is
derived by means of a variational method. In the lowest approximation, the
potential is $N(S+1)\omega_{\perp}(x)$, with $N$ the soliton's norm (number of
atoms), and $S$ its intrinsic vorticity (if any). The results can be used to
devise nonuniform traps helping to control the longitudinal dynamics of the
solitons. Numerical verification of the analytical predictions will be
presented elsewhere.
\\ ( , 223kb)
Paper: cond-mat/0607730
Date: Thu, 27 Jul 2006 16:16:11 GMT (142kb)

Title: Normal state of a polarized Fermi gas at unitarity
Authors: C. Lobo, A. Recati, S. Giorgini, and S. Stringari
Subj-class: Other
   We study the Fermi gas at unitarity and at T=0 by assuming that, at high
polarizations, it is a normal Fermi liquid composed of weakly interacting
quasiparticles associated with the minority spin atoms. With a quantum Monte
Carlo approach we calculate their effective mass and binding energy, as well as
the full equation of state of the normal phase as a function of the
concentration x=n_\down/n_\up of minority atoms. We predict a first order phase
transition from normal to superfluid at x_c=0.44 corresponding, in the presence
of harmonic trapping, to a critical polarization P_c=(N_\up-N_\down)/
(N_\up+N_\down)=77%. We calculate the radii and the density profiles in the
trap and predict that the frequency of the spin dipole mode will be increased
by a factor of 1.23 due to interactions.
\\ ( , 143kb)
Paper: cond-mat/0607735
Date: Thu, 27 Jul 2006 17:41:57 GMT (115kb)

Title: Average ground-state energy of finite Fermi systems
Authors: M. Centelles, P. Leboeuf, A. G. Monastra, J. Roccia, P. Schuck, X.
Comments: 10 pages, 8 figures
Subj-class: Other
   Semiclassical theories like the Thomas-Fermi and Wigner-Kirkwood methods give
a good description of the smooth average part of the total energy of a Fermi
gas in some external potential when the chemical potential is varied. However,
in systems with a fixed number of particles N, these methods overbind the
actual average of the quantum energy as N is varied. We describe a theory that
accounts for this effect. Numerical illustrations are discussed for fermions
trapped in a harmonic oscillator potential and in a hard wall cavity, and for
self-consistent calculations of atomic nuclei. In the latter case, the
influence of deformations on the average behavior of the energy is also
\\ ( , 115kb)
Paper: cond-mat/0601148
replaced with revised version Thu, 27 Jul 2006 15:19:34 GMT (27kb)

Title: Surface Energy in Cold Asymmetrical Fermion Superfluids
Authors: Heron Caldas
Comments: 4 pages, 1 figure, minor corrections, one reference added, title
Subj-class: Superconductivity; Strongly Correlated Electrons
\\ ( , 27kb)
Paper: cond-mat/0602626
replaced with revised version Thu, 27 Jul 2006 12:39:19 GMT (160kb)

Title: Bifurcations in Resonance Widths of an Open Bose-Hubbard Dimer
Authors: M. Hiller, T. Kottos, A. Ossipov
Comments: 4 pages, 3 figures
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 063625 (2006)
\\ ( , 160kb)
Paper: cond-mat/0605218
replaced with revised version Thu, 27 Jul 2006 10:20:31 GMT (42kb)

Title: Supersolid phases in the one dimensional extended soft core Bosonic
   Hubbard model
Authors: G.G. Batrouni, F. Hebert, R.T. Scalettar
Comments: 4 pages, 5 figures
Subj-class: Superconductivity; Statistical Mechanics
\\ ( , 42kb)
Paper: cond-mat/0605695
replaced with revised version Thu, 27 Jul 2006 11:54:56 GMT (123kb)

Title: Chaotic ratchet dynamics with cold atoms in a pair of pulsed optical
Authors: Gabriel G. Carlo, Giuliano Benenti, Giulio Casati, Sandro Wimberger,
   Oliver Morsch, Riccardo Mannella, Ennio Arimondo
Comments: 7 pages, 7 figures
Subj-class: Other; Chaotic Dynamics
\\ ( , 123kb)
Paper: quant-ph/0607197
Date: Thu, 27 Jul 2006 17:10:38 GMT (572kb)

Title: Towards quantum computing with single atoms and optical cavities on atom
Authors: M. Trupke, J. Metz, A. Beige, and E. A. Hinds
Comments: 14 pages, 6 figures
   We report on recent developments in the integration of optical
microresonators into atom chips and describe some fabrication and
implementation challenges. We also review theoretical proposals for quantum
computing with single atoms based on the observation of photons leaking through
the cavity mirrors. The use of measurements to generate entanglement can result
in simpler, more robust and scalable quantum computing architectures. Indeed,
we show that quantum computing with atom-cavity systems is feasible even in the
presence of relatively large spontaneous decay rates and finite photon detector
\\ ( , 572kb)
Paper (*cross-listing*): gr-qc/0603112
replaced with revised version Wed, 26 Jul 2006 20:22:38 GMT (10kb)

Title: Quantum gravitational decoherence of matter waves
Authors: Charles H.-T. Wang, Robert Bingham and J. Tito Mendonca
Comments: 8 pages; final version to appear in CQG as a letter
\\ ( , 10kb)

Till next time (whenever that is),

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
views of the sender and not the views of the University of Queensland
Received on Fri Jul 28 2006 - 19:48:42 EST

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