# Matt's arXiv selection: week ending 6th July 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Wed, 18 Jul 2007 08:53:29 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Hello again,

Before we get into the abstracts this week, I'm going to take the opportunity to
advertise what should be a great conference that is being held in Australia at
the end of 2007:

Quantum-Atom Optics Downunder

December 3-6, 2007
Wollongong, Australia
Novotel North Beach Hotel

ABSTRACT SUBMISSION DEADLINE: 26 July 2007.

Keynote/invited speakers:

Alain Aspect; Inst. d'Optique, France.
Ignacio Cirac; Max-Planck Inst., Germany.
Joseph Eberly; Univ. of Rochester, USA.
Philippe Grangier; Inst. d'Optique, France.
Hideo Mabuchi; Caltech, USA.
William Phillips; NIST, USA.
Eugene Polzik; QUANTOP, Denmark.
Blair Blakie; Univ. of Otago, New Zealand
Wolfgang Ertmer; Inst. of Quantum Optics, Univ. of Hannover, Germany
Claude Fabre; Lab Kastler Brossel, Univ. Pierre et Marie Curie, France.
Daniel J. Heinzen; Univ. of Texas, USA.
Murray Holland; Univ. of Colorado, USA.
Massimo Inguscio; European Lab for Non-linear Spectroscopy, Italy.
Ping Koy Lam; Australian Natl. Univ., Australia.

End of advertising. This week there are 29 new preprints and 11 replacements

------------------------------------------------------------------------------
\\
arXiv:0706.4310
Date: Thu, 28 Jun 2007 20:00:03 GMT (60kb)

Title: Exotic phase diagram of a cluster charging model of bosons on the kagome
lattice
Authors: Sergei V. Isakov, Arun Paramekanti, Yong Baek Kim
Categories: cond-mat.str-el
Comments: 11 pages, 10 figures
\\
We study a model of hard-core bosons on the kagome lattice with short-range
hopping ($t$) and repulsive interactions ($V$). This model directly maps on to
an easy-axis $S=1/2$ XXZ model on the kagome lattice and is also related, by a
duality transformation at large $V/t$, to a quantum dimer model on the
triangular lattice. Using quantum Monte Carlo (QMC) numerics, we map out the
phase diagram of this model at half-filling. At T=0, we show that this model
exhibits a superfluid phase at small $V/t$ and an insulating phase at large
$V/t$, separated by a continuous quantum phase transition at $V_c/t \approx 19.8$. The insulating phase at T=0 appears to have no conventional broken
symmetries, and is thus a uniform Mott insulator (a spin liquid' in magnetic
language). We characterize this insulating phase as a uniform $Z_2$
fractionalized insulator from the topological order in the ground state and
estimate its vison gap. Consistent with this identification, there is no
apparent thermal phase transition upon heating the insulator. The insulating
phase instead smoothly crosses over into the high temperature paramagnet via an
intermediate cooperative paramagnetic regime. We also study the
superfluid-to-normal thermal transition for $V < V_c$. We find that this is a
Kosterlitz-Thouless transition at small $V/t$ but changes to a first order
transition for $V$ closer to $V_c$. We argue that this first order thermal
transition is consistent with the presence of a nearby $Z_2$ insulating ground
state obtained from the superfluid ground state by condensing double vortices.
\\ ( http://arxiv.org/abs/0706.4310 , 60kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4320
Date: Thu, 28 Jun 2007 20:52:54 GMT (89kb)

Title: Realization of Levy flights as continuous processes
Authors: Ihor Lubashevsky, Rudolf Friedrich, Andreas Heuer
Categories: cond-mat.stat-mech cond-mat.mtrl-sci
Comments: paper of 5 pages with 3 figures with added supplementary materials
\\
On the basis of multivariate Langevin processes we present a realization of
Levy flights as a continuous process. For the simple case of a particle moving
under the influence of friction and a velocity dependent stochastic force we
explicitly derive the generalized Langevin equation and the corresponding
generalized Fokker-Planck equation describing Levy flights. Our procedure is
similar to the treatment of the Kramers-Fokker Planck equation in the
Smoluchowski limit. The proposed approach forms a feasible way of tackling Levy
flights in inhomogeneous media or systems with boundaries what is up to now a
challenging problem.
\\ ( http://arxiv.org/abs/0706.4320 , 89kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4434
Date: Fri, 29 Jun 2007 15:04:08 GMT (62kb)

Title: Pairing of 1D Bose-Fermi mixtures with unequal masses
Authors: M. Rizzi, A. Imambekov
Categories: cond-mat.str-el cond-mat.other
Comments: 7 pages, 5 figures
\\
We have considered one dimensional Bose-Fermi mixture with equal densities
and unequal masses using DMRG. For the mass ratio of K-Rb mixture and
attraction between bosons and fermions, we determined the phase diagram. For
weak boson-boson interactions, there is a direct transition between
two-component Luttinger liquid and collapsed phases as the boson-fermion
attraction is increased. For strong enough boson-boson interactions, we find an
intermediate ''paired phase, which is a single-component Luttinger liquid of
composite particles. We investigated correlation functions of such ''paired
phase, studied the stability of "paired" phase to density imbalance, and
discussed various experimental techniques which can be used to detect it.
\\ ( http://arxiv.org/abs/0706.4434 , 62kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4335
Date: Thu, 28 Jun 2007 23:36:55 GMT (489kb)

Title: A single-photon transistor using nano-scale surface plasmons
Authors: D.E. Chang, A.S. S{\o}rensen, E.A. Demler, and M.D. Lukin
Categories: quant-ph
Comments: 20 pages, 4 figures
\\
It is well known that light quanta (photons) can interact with each other in
nonlinear media, much like massive particles do, but in practice these
interactions are usually very weak. Here we describe a novel approach to
realize strong nonlinear interactions at the single-photon level. Our method
makes use of recently demonstrated efficient coupling between individual
optical emitters and tightly confined, propagating surface plasmon excitations
on conducting nanowires. We show that this system can act as a nonlinear
two-photon switch for incident photons propagating along the nanowire, which
can be coherently controlled using quantum optical techniques. As a novel
application, we discuss how the interaction can be tailored to create a
single-photon transistor, where the presence or absence of a single incident
photon in a gate'' field is sufficient to completely control the propagation
of subsequent signal'' photons.
\\ ( http://arxiv.org/abs/0706.4335 , 489kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4438
Date: Fri, 29 Jun 2007 15:10:43 GMT (16kb)

Title: Quantum jumps with negative probabilities
Authors: J. Piilo, S. Maniscalco, and K.-A. Suominen
Categories: quant-ph
Comments: 4 pages, 3 figures
\\
Experiments with trapped particles have demonstrated the existence of quantum
jumps and the discrete nature of single-system dynamics in quantum mechanics.
The concept of jumps is also a powerful tool for simulating and understanding
open quantum systems. In non-Markovian systems jump probabilities can become
negative due to the memory effects between the system and its environment. We
present a method that can handle both positive and negative probabilities and
provides powerful insight into the dynamics of open systems with memory. The
key element is a reversed quantum jump to a system state that was, in
principle, already destroyed by an earlier normal jump. Instead of using
artificial extensions of the system or exploiting hidden variables we take
advantage of the information stored in the quantum ensemble itself.
\\ ( http://arxiv.org/abs/0706.4438 , 16kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4479
Date: Fri, 29 Jun 2007 19:45:48 GMT (959kb,D)

Title: Experimental characterization of frequency dependent squeezed light
Authors: Simon Chelkowski, Henning Vahlbruch, Boris Hage, Alexander Franzen,
Nico Lastzka, Karsten Danzmann and Roman Schnabel
Categories: quant-ph
Comments: 8 pages, 8 figures
Journal-ref: Physical Review A 71, 013806 (2005)
\\
We report on the demonstration of broadband squeezed laser beams that show a
frequency dependent orientation of the squeezing ellipse. Carrier frequency as
well as quadrature angle were stably locked to a reference laser beam at
1064nm. This frequency dependent squeezing was characterized in terms of noise
power spectra and contour plots of Wigner functions. The later were measured by
quantum state tomography. Our tomograph allowed a stable lock to a local
oscillator beam for arbitrary quadrature angles with one degree precision.
Frequency dependent orientations of the squeezing ellipse are necessary for
squeezed states of light to provide a broadband sensitivity improvement in
third generation gravitational wave interferometers. We consider the
application of our system to long baseline interferometers such as a future
squeezed light upgraded GEO600 detector.
\\ ( http://arxiv.org/abs/0706.4479 , 959kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4218
Date: Thu, 28 Jun 2007 12:55:05 GMT (169kb)

Title: Association of heteronuclear molecules in a harmonic oscillator well
Authors: Jesper Fevre Bertelsen and Klaus Molmer
Categories: cond-mat.other quant-ph
Comments: 10 pages, 4 figures
\\
We describe the collisional interaction between two different atoms that are
trapped in a harmonic potential. The atoms are exposed to a magnetic field,
which is modulated in the vicinity of an s-wave Feshbach resonance, and we
study the formation of molecular bound states and excited states of the trapped
system with non-trivial angular correlations.
\\ ( http://arxiv.org/abs/0706.4218 , 169kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0083
Date: Sat, 30 Jun 2007 23:28:46 GMT (23kb)

Title: On Sound Reflection in Superfluid
Authors: L.A.Melnikovsky
Categories: cond-mat.supr-con
Comments: 9 pages, 4 figures
\\
We consider reflection of the first and the second sound waves by a rigid
flat wall in superfluid. Nontrivial dependence of the reflection coefficients
on the angle of incidence is obtained. Sound conversion is predicted at slanted
incidence.
\\ ( http://arxiv.org/abs/0707.0083 , 23kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0145
Date: Mon, 2 Jul 2007 05:49:30 GMT (33kb)

Title: Laser Pulse Amplification with Bose-Einstein Condensates
Authors: Alphan Sennaroglu, Ozgur E. Mustecaplioglu, Devrim Tarhan
Categories: cond-mat.other
Comments: 4 pages, 5 figures, submitted to Phys. Rev. Lett
\\
We propose a pulse amplification scheme based on a Bose-Einstein condensate
(BEC) introduced inside the resonator of a mode-locked laser. Ultraslow light
propagation through the BEC can lead to a considerable increase in the cavity
round-trip delay time, lower the effective repetition rate of the laser, and
hence scale up the output pulse energy. We present simulations that support the
feasibility of this amplification scheme by using a sodium ($^{23}$Na) BEC as
an example. Our results show that, depending on the temperature, pulse energy
amplification factors of the order of $\sim 10^3$ are possible at an effective
condensate length of $\sim 10-100$ $\mu$m. To compensate for the group velocity
dispersion introduced by the BEC, we further propose the use of a second
compensating BEC with the opposite sign of dispersion to cancel the pulse
chirp. We determine adjustable BEC parameters to find an operating point where
the total dispersion was zero. Finally, we discuss the bandwidth limitations of
the amplifier and estimate the minimum temporal width of the pulse that can be
amplified with this technique.
\\ ( http://arxiv.org/abs/0707.0145 , 33kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0307
Date: Mon, 2 Jul 2007 20:26:53 GMT (644kb)

Title: Quasi-angular momentum of Bose and Fermi gases in rotating optical
lattices
Authors: Brandon M. Peden, Rajiv Bhat, Meret Kr\"{a}mer and Murray J. Holland
Categories: cond-mat.other
Comments: 20 pages, 12 figures, submitted to J. Phys. B
\\
The notion of quasi-angular momentum is introduced to label the eigenstates
of a Hamiltonian with a discrete rotational symmetry. This concept is recast in
an operatorial form where the creation and annihilation operators of a Hubbard
Hamiltonian carry units of quasi-angular momentum. Using this formalism, the
ground states of ultracold gases of non-interacting fermions in rotating
optical lattices are studied as a function of rotation, and transitions between
states of different quasi-angular momentum are identified. In addition,
previous results for strongly-interacting bosons are re-examined and compared
to the results for non-interacting fermions. Quasi-angular momentum can be used
to distinguish between these two cases. Finally, an experimentally accessible
signature of quasi-angular momentum is identified in the momentum distributions
of single-particle eigenstates.
\\ ( http://arxiv.org/abs/0707.0307 , 644kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0383
Date: Tue, 3 Jul 2007 10:26:15 GMT (232kb)

Title: Pair condensation of bosonic atoms induced by optical lattices
Authors: Maria Eckholt, Juan Jose Garcia-Ripoll
Categories: cond-mat.other
\\
We design a model of correlated hopping for bosonic atoms in optical
lattices. Such model exhibits three kinds of phases, comprehending a Mott
insulator, a charge density wave and a pair quasi-condensate. The
implementation of the model relies on two-state atoms embedded in
state-dependent lattices and having spin-dependent interactions. Contrary to
other models of pairing, our design is not based on perturbative effects and
should be observable in current experiments.
\\ ( http://arxiv.org/abs/0707.0383 , 232kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0403
Date: Tue, 3 Jul 2007 12:40:50 GMT (68kb)

Title: Dynamical control of matter-wave tunneling in periodic potentials
Authors: H. Lignier and C. Sias and D. Ciampini and Y. Singh and A. Zenesini
and O. Morsch and E. Arimondo
Categories: cond-mat.other
Comments: 5 pages, 3 figures
\\
We report on measurements of dynamical suppression of inter-well tunneling of
a Bose-Einstein condensate (BEC) in a strongly driven optical lattice. The
strong driving is a sinusoidal shaking of the lattice corresponding to a
time-varying linear potential, and the tunneling is measured by letting the BEC
freely expand in the lattice. The measured tunneling rate is reduced and, for
certain values of the shaking parameter, completely suppressed. Our results are
in excellent agreement with theoretical predictions. Furthermore, we have
verified that in general the strong shaking does not destroy the phase
coherence of the BEC, opening up the possibility of realizing quantum phase
transitions by using the shaking strength as the control parameter.
\\ ( http://arxiv.org/abs/0707.0403 , 68kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0441
Date: Tue, 3 Jul 2007 15:28:10 GMT (29kb)

Title: Kelvon-roton instability of vortex lines in dipolar Bose-Einstein
condensates
Authors: M. Klawunn, R. Nath, P. Pedri and L. Santos
Categories: cond-mat.other
Comments: 4 pages, 3 eps figures
\\
The physics of vortex lines in dipolar condensates is studied. Due to the
nonlocality of the dipolar interaction, the 3D character of the vortex plays a
more important role in dipolar gases than in typical short-range interacting
ones. In particular, the dipolar interaction significantly affects the
stability of the transverse modes of the vortex line. Remarkably, in the
presence of a periodic potential along the vortex line, a roton minimum may
develop in the spectrum of transverse modes. We discuss the appropriate
conditions at which this roton minimum may eventually lead to an instability of
the straight vortex line, opening new scenarios for vortices in dipolar gases.
\\ ( http://arxiv.org/abs/0707.0441 , 29kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0453
Date: Tue, 3 Jul 2007 16:00:32 GMT (417kb)

Title: Bose-Einstein condensates under a spatially-modulated transverse
confinement
Authors: L. Salasnich, A. Cetoli, B.A. Malomed, F. Toigo, and L. Reatto
Categories: cond-mat.other
Comments: 10 pages, 10 figures, accepted for publication in Phys. Rev. A
\\
We derive an effective nonpolynomial Schrodinger equation (NPSE) for
self-repulsive or attractive BEC in the nearly-1D cigar-shaped trap, with the
transverse confining frequency periodically modulated along the axial
direction. Besides the usual linear cigar-shaped trap, where the periodic
modulation emulates the action of an optical lattice (OL), the model may be
also relevant to toroidal traps, where an ordinary OL cannot be created. For
either sign of the nonlinearity, extended and localized states are found, in
the numerical form (using both the effective NPSE and the full 3D
Gross-Pitaevskii equation) and by means of the variational approximation (VA).
The latter is applied to construct ground-state solitons and predict the
collapse threshold in the case of self-attraction. It is shown that numerical
solutions provided by the one-dimensional NPSE are always very close to full 3D
solutions, and the VA yields quite reasonable results too. The transition from
delocalized states to gap solitons, in the first finite bandgap of the linear
spectrum, is examined in detail, for the repulsive and attractive
nonlinearities alike.
\\ ( http://arxiv.org/abs/0707.0453 , 417kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0458
Date: Tue, 3 Jul 2007 16:31:23 GMT (55kb)

Title: Number fluctuations in cold quantum gases
Authors: G.E. Astrakharchik, R. Combescot, L.P. Pitaevskii
Categories: cond-mat.stat-mech
\\
In ultracold gases many experiments use atom imaging as a basic observable.
The resulting image is averaged over a number of realizations and mostly only
this average is used. Only recently the noise has been measured to extract
physical information. In the present paper we investigate the quantum noise
arising in these gases at zero temperature. We restrict ourselves to the
homogeneous situation and study the fluctuations in particle number found
within a given volume in the gas, and more specifically inside a sphere of
radius R. We show that zero-temperature fluctuations are not extensive and the
leading term scales with sphere radius R as R^2ln(R) (or ln(R)) in three- (or
one-) dimensional systems. We calculate systematically the next term beyond
this leading order. We consider first the generic case of a compressible
superfluid. Then we investigate the whole BEC-BCS crossover, and in particular
the limiting cases of the weakly interacting Bose gas and of the free Fermi
gas.
\\ ( http://arxiv.org/abs/0707.0458 , 55kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0460
Date: Tue, 3 Jul 2007 16:37:11 GMT (99kb)

Title: Gaussian potentials facilitate access to quantum Hall states in rotating
Bose gases
Authors: Alexis G. Morris, David L. Feder
Categories: cond-mat.mes-hall
Comments: 4 pages, 4 figures
\\
Through exact numerical diagonalization for small numbers of atoms, we show
that it is possible to access quantum Hall states in harmonically confined Bose
gases at rotation frequencies well below the centrifugal limit by applying a
repulsive Gaussian potential at the trap center. The main idea is to reduce or
eliminate the effective trapping frequency in regions where the particle
density is appreciable. The critical rotation frequency required to obtain the
bosonic Laughlin state can be fixed at an experimentally accessible value by
choosing an applied Gaussian whose amplitude increases linearly with the number
of atoms while its width increases as the square root.
\\ ( http://arxiv.org/abs/0707.0460 , 99kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0379
Date: Tue, 3 Jul 2007 10:09:51 GMT (226kb)

Title: Dependence of Resonant Absorption Linewidth on Atomic Vapour Column
Thickness for D1 Line of Cs Atoms Confined in Nano-Cell
Authors: A. Sargsyan, D. Sarkisyan, Y. Pashayan-Leroy, C. Leroy, P. Moroshkin,
A. Weis
Categories: physics.atom-ph
Comments: 13 pages
\\
A new nano-cell with smoothly varying longitudinal thickness of the atomic
vapour layer L in the range of 350 - 5100 nm allowing to study the resonant
absorption of D1 and D2 lines of Cs atoms for thicknesses changing from L =
Lambda/2 to L = 6Lambda with the step of Lambda /2 (Lambda = 894 nm is the
resonant laser wavelength) and for different intensities is developed. It is
revealed that for low laser intensities there is narrowing of the resonant
absorption spectrum for the thicknesses from L = (2n + 1) Lambda (where n is an
integer) up to L = 7/2 Lambda and broadening of the spectrum for L = n Lambda.
For relatively high laser intensity (>1 mW/cm2), velocity selective optical
pumping/saturated resonances of a reduced absorption (with the line-width close
to the natural one), and centred on the hyperfine transitions occur When L = n
Lambda. The possible application of these resonance peaks is given. The
developed theoretical model describes well the experiment.
\\ ( http://arxiv.org/abs/0707.0379 , 226kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0613
Date: Wed, 4 Jul 2007 13:58:13 GMT (125kb)

Title: Ferromagnetic behaviour in the strongly interacting two-component Bose
gas
Authors: X.-W. Guan, M.T. Batchelor and M. Takahashi
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 15 pages, 6 figures
\\
We investigate the low temperature behaviour of the integrable 1D
two-component spinor Bose gas using the thermodynamic Bethe ansatz. We find
that for strong coupling the characteristics of the thermodynamics at low
temperatures are quantitatively affected by the spin ferromagnetic states,
which are described by an effective ferromagnetic Heisenberg chain. The free
energy, specific heat, susceptibility and local pair correlation function are
calculated for various physical regimes in terms of temperature and interaction
strength. These thermodynamic properties reveal spin effects which are
significantly different than those of the spinless Bose gas. The zero-field
susceptibility for finite strong repulsion exceeds that of a free spin
paramagnet. The critical exponents of the specific heat $c_v \sim T^{1/2}$ and
the susceptibility $\chi \sim T^{-2}$ are indicative of the ferromagnetic
signature of the two-component spinor Bose gas. Our analytic results are
consistent with general arguments by Eisenberg and Lieb for polarized spinor
bosons.
\\ ( http://arxiv.org/abs/0707.0613 , 125kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0675
Date: Wed, 4 Jul 2007 17:54:37 GMT (227kb)

Title: Disorder-Induced Order in Two-Component Bose-Einstein Condensates
Authors: Armand Niederberger, Thomas Schulte, Jan Wehr, Maciej Lewenstein,
Laurent Sanchez-Palencia, Krzysztof Sacha
Categories: cond-mat.other cond-mat.dis-nn
Comments: 4 pages, 3 figures
\\
We propose and analyze a general mechanism of disorder-induced order in
two-component Bose-Einstein condensates, analogous to corresponding effects
established for XY spin models. We show that a random Raman coupling induces a
relative phase of \pi/2 between two BECs and that the effect is robust. We
demonstrate it in 1D, 2D and 3D at T=0 and present evidences that it persists
for small T>0. Applications to phase control in ultracold spinor condensates
are discussed.
\\ ( http://arxiv.org/abs/0707.0675 , 227kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0270 (*cross-listing*)
Date: Mon, 2 Jul 2007 16:46:52 GMT (14kb)

Title: The Sagnac effect in superfluids
Authors: E. Varoquaux and G. Varoquaux
Categories: gr-qc cond-mat.other
Comments: Letter to the Editors of Uspheki Fisiki Nauk - 4 pages
\\
We comment on the interpretation of absolute rotation measurements with
superfluids, which involve the Sagnac effect. This effect, first observed in
rotating optical interferometers, has now been seen in a host of different
physical systems, ranging from atomic clocks to electrons, neutrons, atomic
beams, ... We show that the time-honored explanation of this effect based on
general relativity provides a common explanation for all these systems,
including superfluids, in contradistinction with the views expressed in a
recent review article.
\\ ( http://arxiv.org/abs/0707.0270 , 14kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0496
Date: Tue, 3 Jul 2007 20:35:12 GMT (874kb)

Title: Controlled spontaneous emission
Authors: Jae-Seung Lee, Mary A. Rohrdanz, and A. K. Khitrin
Categories: quant-ph
Comments: 25 pages including 11 figures
\\
The problem of spontaneous emission is studied by a direct computer
simulation of the dynamics of a combined system: atom + radiation field. The
parameters of the discrete finite model, including up to 20k field oscillators,
have been optimized by a comparison with the exact solution for the case when
the oscillators have equidistant frequencies and equal coupling constants.
Simulation of the effect of multi-pulse sequence of phase kicks and emission by
a pair of atoms shows that both the frequency and the linewidth of the emitted
spectrum could be controlled.
\\ ( http://arxiv.org/abs/0707.0496 , 874kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0695
Date: Wed, 4 Jul 2007 20:48:16 GMT (67kb)

Title: Novel Transitions in S=1 Spinor Condensates and XY Ashkin-Teller
Universality
Authors: Daniel Podolsky, Shailesh Chandrasekharan, and Ashvin Vishwanath
Categories: cond-mat.stat-mech
Comments: 4 pages, 4 figures
\\
We study spin-1 polar spinor condensates with magnetic anisotropy, in two
spatial dimensions at finite temperatures. The topological binding of vorticity
to nematic disclinations leads to a rich phase diagram, which is captured by
aU(1) version of the Ashkin-Teller model. In particular, a
"cascaded"Kosterlitz-Thouless critical point, with two diverging scales, is
predicted.
Numerical simulations are performed to check our picture.
\\ ( http://arxiv.org/abs/0707.0695 , 67kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0709
Date: Thu, 5 Jul 2007 00:16:23 GMT (42kb)

Title: Dipolar Bose-Einstein condensates at Finite temperature
Authors: Shai Ronen and John Bohn
Categories: cond-mat.stat-mech
Comments: 9 figures
\\
We study a Bose-Einstein condensate (BEC) of a dilute gas with dipolar
interactions, at finite temperature, using the Hartree-Fock-Bogoliubov (HFB)
theory within the Popov approximation. An additional approximation involving
the dipolar exchange interaction is made to facilitate the computation. We
calculate the temperature dependence of the condensate fraction of a condensate
confined in a cylindrically symmetric harmonic trap. We show that the
bi-concave shaped condensates found in Ref. \cite{Ronen07} in certain pancake
traps at zero temperature, are also stable at finite temperature. Surprisingly,
the dip in the central density of these structured condensates is
actuallyenhanced at low finite temperatures. We explain this effect.\\ (
http://arxiv.org/abs/0707.0709 , 42kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0776
Date: Thu, 5 Jul 2007 13:19:11 GMT (74kb)

Title: Damping of bulk excitations over an elongated BEC - the role of radial
modes
Authors: E. E. Rowen, N. Bar-Gill, R. Pugatch, N. Davidson
Categories: cond-mat.other
Comments: 5 pages, 4 figures\\ We report the measurement of Beliaev damping of
bulk excitations in cigar
shaped Bose Einstein condensates of atomic vapor. By using post selection,
excitation line shapes of the total population are compared with those of the
undamped excitations. We find that the damping depends on the initial
excitation energy of the decaying quasi particle, as well as on the excitation
momentum. We model the condensate as an infinite cylinder and calculate the
damping rates of the different radial modes. The derived damping rates are in
good agreement with the experimentally measured ones. The damping rates
strongly depend on the destructive interference between pathways for damping,
due to the quantum many-body nature of both excitation and damping products.
\\ ( http://arxiv.org/abs/0707.0776 , 74kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0792
Date: Thu, 5 Jul 2007 15:28:49 GMT (30kb)

Title: Theory of RF-spectroscopy of strongly interacting Fermions
Authors: M. Punk, W. Zwerger
Categories: cond-mat.other
Comments: 4 pages, 3 figures, RevTex4
\\
We show that strong pairing correlations in Fermi gases lead to the
appearance of a gap-like structure in the RF-spectrum, both in the balanced
superfluid and in the normal phase above the Clogston-Chandrasekhar limit. In
the balanced case, the average shift of the RF-spectrum is determined by the
momentum distribution at large wavevectors. In the strongly imbalanced case,
the RF-spectrum measures the binding energy of a minority atom to the Fermi sea
of majority atoms. Our results provide a qualitative understanding of recent
experiments by Schunck et.al.
\\ ( http://arxiv.org/abs/0707.0792 , 30kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0794
Date: Thu, 5 Jul 2007 14:43:50 GMT (319kb)

Title: Field-theoretic methods
Authors: Uwe C. Tauber
Categories: cond-mat.stat-mech
Comments: Article for the Encyclopedia of Complexity and System Science, B.
Meyers (Ed.), Springer-Verlag Berlin, 2008
\\
Many complex systems are characterized by intriguing spatio-temporal
structures. Their mathematical description relies on the analysis of
appropriate correlation functions. Functional integral techniques provide a
unifying formalism that facilitates the computation of such correlation
functions and moments, and furthermore allows a systematic development of
perturbation expansions and other useful approximative schemes. It is explained
how nonlinear stochastic processes may be mapped onto exponential probability
distributions, whose weights are determined by continuum field theory actions.
Such mappings are madeexplicit for (1) stochastic interacting particle systems
whose kinetics is defined through a microscopic master equation; and (2)
nonlinear Langevin stochastic differential equations which provide a mesoscopic
description wherein a separation of time scales between the relevant degrees of
freedom and background statistical noise is assumed. Several well-studied
examples are introduced to illustrate the general methodology.
\\ ( http://arxiv.org/abs/0707.0794 , 319kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0833
Date: Thu, 5 Jul 2007 16:57:51 GMT (6kb)

Title: Kirzhnits gradient expansion for a D-dimensional Fermi gas
Authors: Luca Salasnich (CNR-Infm and Cnism)
Categories: cond-mat.stat-mech cond-mat.other
Comments: 6 pages, 0 figures, accepted for publication in J. Phys. A: Math.
Theor
\\
For an ideal D-dimensional Fermi gas under generic external confinement we
derive the correcting coefficient $(D-2)/3D$ of the von Weizsacker term in the
kinetic energy density. To obtain this coefficient we use the Kirzhnits
semiclassical expansion of the number operator up to the second order in the
Planck constant $\hbar$. Within this simple and direct approach we determine
the differential equation of the density profile and the density functional of
the Fermi gas. In the case D=2 we find that the Kirzhnits gradient corrections
vanish to all order in $\hbar$.
\\ ( http://arxiv.org/abs/0707.0833 , 6kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0859
Date: Thu, 5 Jul 2007 19:43:06 GMT (334kb)

Title: Coherence and clock shifts in ultracold Fermi gases with resonant
interactions
Authors: Gordon Baym, C. J. Pethick, Zhenhua Yu, and Martin W. Zwierlein
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 2 figures. Nordita preprint NORDITA-2007-23
\\
Using arguments based on sum rules, we derive a general result for the
average shifts of rf lines in Fermi gases in terms of interatomic interaction
strengths and two-particle correlation functions. We show that near an
interaction resonance shifts vary inversely with the atomic scattering length,
rather than linearly as in dilute gases, thus accounting for the experimental
observation that clock shifts remain finite at Feshbach resonances.
\\ ( http://arxiv.org/abs/0707.0859 , 334kb)
------------------------------------------------------------------------------
\\
arXiv:0707.0720
Date: Thu, 5 Jul 2007 06:03:37 GMT (132kb)

Title: Non-classical photon pair generation in atomic vapours
Authors: S. N.Sandhya
Categories: quant-ph
Comments: 18 pages, 7 figures
Journal-ref: Phys. Rev. A 76 013802 (2007)
\\
A scheme for the generation of non-classical pairs of photons in atomic
vapours is proposed. The scheme exploits the fact that the cross correlation of
the emission of photons from the extreme transitions of a four-level cascade
system shows anti-bunching which has not been reported earlier and which is
unlike the case of the three level cascade emission which shows bunching. The
Cauchy-Schwarz inequality which is the ratio of cross-correlation to the auto
correlation function in this case is estimated to be $10^3-10^6$ for
controllable time delay, and is one to four orders of magnitude larger compared
to previous experiments. The choice of Doppler free geometry in addition to the
fact that at three photon resonance the excitation/deexcitation processes occur
in a very narrow frequency band, ensures cleaner signals.
\\ ( http://arxiv.org/abs/0707.0720 , 132kb)
------------------------------------------------------------------------------

The replacements:

------------------------------------------------------------------------------
\\
arXiv:0706.0240
replaced with revised version Fri, 29 Jun 2007 17:54:33 GMT (113kb)

Title: KRb Feshbach Resonances: Modeling the interatomic potential
Authors: C. Klempt, T. Henninger, O. Topic, J. Will, W. Ertmer, E. Tiemann and
J. Arlt
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0706.0240 , 113kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4041
replaced with revised version Fri, 29 Jun 2007 00:53:46 GMT (975kb)

Title: Matter-wave Interferometry with Phase Fluctuating Bose-Einstein
Condensates
Authors: G.-B. Jo, J.-H. Choi, C.A. Christensen, Y.-R. Lee, T.A. Pasquini, W.
Ketterle, and D.E. Pritchard
Categories: cond-mat.other
Comments: 4 pages, 5 figures
\\ ( http://arxiv.org/abs/0706.4041 , 975kb)
------------------------------------------------------------------------------
\\
arXiv:0706.4260
replaced with revised version Fri, 29 Jun 2007 06:24:02 GMT (330kb)

Title: Ultracold Bose gases in time-dependent 1D superlattices: response and
quasimomentum structure
Authors: Markus Hild, Felix Schmitt, Ilona T\"urschmann, Robert Roth
Categories: cond-mat.stat-mech
Comments: 4 pages, 4 figures
\\ ( http://arxiv.org/abs/0706.4260 , 330kb)
------------------------------------------------------------------------------
\\
arXiv:0704.2263
replaced with revised version Mon, 2 Jul 2007 05:40:53 GMT (229kb)

Title: Nonlinearity-assisted quantum tunneling in a matter-wave interferometer
Authors: Chaohong Lee, Elena A. Ostrovskaya, Yuri S. Kivshar
Categories: cond-mat.other
Comments: 11 pages, 6 figures
\\ ( http://arxiv.org/abs/0704.2263 , 229kb)
------------------------------------------------------------------------------
\\
arXiv:0706.2744
replaced with revised version Sun, 1 Jul 2007 12:35:28 GMT (401kb,D)

Title: Dynamical instabilities of Bose-Einstein condensates at the band-edge in
one-dimensional optical lattices
Authors: Andrew J. Ferris, Matthew J. Davis, Reece W. Geursen, P. Blair Blakie,
Andrew C. Wilson
Categories: cond-mat.other quant-ph
Comments: v2: Added several references
\\ ( http://arxiv.org/abs/0706.2744 , 401kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0610830
replaced with revised version Tue, 3 Jul 2007 08:39:23 GMT (19kb)

Title: Persistent currents in a Bose-Einstein condensate in the presence of
disorder
Authors: M. Ogren, G. M. Kavoulakis (LTH, Lund)
Categories: cond-mat.other
Comments: 5 pages, RevTex, 3 figures, revised version, to appear in JLTP
\\ ( http://arxiv.org/abs/cond-mat/0610830 , 19kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0610121
replaced with revised version Wed, 4 Jul 2007 08:36:26 GMT (85kb)

Title: Phase separation in a two species Bose mixture
Authors: T. Mishra, Ramesh V. Pai, B. P. Das
Categories: cond-mat.stat-mech cond-mat.other
Comments: 7 pages, 7 figures
Journal-ref: Phys. Rev. A 76, 013604 (2007) (6 pages)
\\ ( http://arxiv.org/abs/cond-mat/0610121 , 85kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0611230
replaced with revised version Tue, 3 Jul 2007 21:14:10 GMT (17kb)

Title: Classifying Vortices in S=3 Bose-Einstein Condensates
Authors: Ryan Barnett, Ari Turner, Eugene Demler
Categories: cond-mat.str-el
Journal-ref: Phys. Rev. A 76, 013605 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0611230 , 17kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0701481
replaced with revised version Wed, 4 Jul 2007 08:39:20 GMT (563kb)

Title: The effects of optically induced non-Abelian gauge field in cold atoms
Authors: Li-Hua Lu and You-Quan Li
Categories: cond-mat.other cond-mat.mes-hall
Comments: Revtex 6 pages, 2 figures, version to be published in PRA
\\ ( http://arxiv.org/abs/cond-mat/0701481 , 563kb)
------------------------------------------------------------------------------
\\
arXiv:0705.2319
replaced with revised version Thu, 5 Jul 2007 16:36:25 GMT (261kb)

Title: Coherence Properties of a Bose-Einstein Condensate in an Optical
Superlattice
Authors: Aranya B Bhattacherjee
Categories: cond-mat.stat-mech
Comments: 12 pages, 5 figures
\\ ( http://arxiv.org/abs/0705.2319 , 261kb)
------------------------------------------------------------------------------
\\
arXiv:0705.3298
replaced with revised version Thu, 5 Jul 2007 14:57:54 GMT (142kb)

Title: Bogoliubov spectrum of a cigar shaped Fermi superfluid in an optical
lattice at the BEC-BCS crossover
Authors: Aranya B Bhattacherjee
Categories: cond-mat.stat-mech
Comments: 7 pages, 2 figures
\\ ( http://arxiv.org/abs/0705.3298 , 142kb)
------------------------------------------------------------------------------

Till next time,
Matt.

--
=========================================================================
Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email: mdavis_at_physics.uq.edu.au
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Australia.                    http://www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
=========================================================================
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 Wed Jul 18 2007 - 08:53:29 EST

This archive was generated by hypermail 2.2.0 : Thu May 08 2008 - 11:51:41 EST