From: Matthew Davis <mdavis_at_physics.uq.edu.au>

Date: Wed, 18 Jul 2007 08:53:29 +1000 (EST)

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

Website: http://www.osa.org/meetings/topicalmeetings/qao/default.aspx

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

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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The replacements:

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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

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