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

Date: Mon, 3 Jul 2006 10:03:57 +1000 (EST)

Date: Mon, 3 Jul 2006 10:03:57 +1000 (EST)

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

This week's email is on time and hence a little shorter!

A highlight this week is a review article:

"Ultracold atomic gases in optical lattices: Mimicking condensed matter

physics and beyond"

by Maciej Lewenstein and co-authors.

Home page: http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/

The abstracts:

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Paper: cond-mat/0606672

Date: Mon, 26 Jun 2006 20:03:43 GMT (14kb)

Title: Shot noise of amplitude of interference between independent atomic

systems

Authors: Anatoli Polkovnikov

Comments: 5 pages, 1 figure

Subj-class: Statistical Mechanics; Disordered Systems and Neural Networks

\\

We study shot (counting) noise of the amplitude of interference between

independent atomic systems. We show that for the two interfering systems the

variance of fringe amplitudes decreases as inverse power of the number of

particles per system with the coefficient being a non-universal number. This

number depends on the details of the initial state of each system implying that

the shot noise measurements can be used to distinguish between different

interfering states. We explicitly evaluate this coefficient for the two cases

of interference between bosons in two number states and in two broken symmetry

states with uncorrelated phases. We generalize our analysis to the interference

of multiple independent atomic systems. We show that the variance of the

properly defined interference contrast vanishes inversely proportionally to the

number of systems. This result, implying high signal to noise ratio in the

experiments measuring interference between multiple independent systems, holds

both for bosons and for fermions.

\\ ( http://arXiv.org/abs/cond-mat/0606672 , 14kb)

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Paper: cond-mat/0606677

Date: Tue, 27 Jun 2006 19:12:13 GMT (635kb)

Title: Response of Bose gases in time-dependent optical superlattices

Authors: M. Hild, F. Schmitt, R. Roth

Comments: 19 pages, 9 figures

Subj-class: Statistical Mechanics

\\

The dynamic response of ultracold Bose gases in one-dimensional optical

lattices and superlattices is investigated based on an exact numerical time

evolution in the framework of the Bose-Hubbard model. The system is excited by

a temporal amplitude modulation of the lattice potential, as it was already

realized in experiment. For regular lattice potentials, the dynamic signatures

of the superfluid to Mott-insulator transition are studied and the position and

the fine-structure of the resonances is explained by a linear response

analysis. This serves as a preparation for the investigation of dynamical

signatures of quantum phase transitions in two-colour superlattice potentials.

Using direct simulations as well as a perturbative analysis it is shown that

the excitation spectrum changes significantly when going from the homogeneous

Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally

accessible signature for the quasi Bose-glass is the appearance of low-lying

resonances and a suppression of the dominant resonance of the Mott-insulator

phase.

\\ ( http://arXiv.org/abs/cond-mat/0606677 , 635kb)

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Paper: cond-mat/0606684

Date: Tue, 27 Jun 2006 07:44:09 GMT (319kb)

Title: Boojums in Rotating Two-Component Bose-Einstein Condensates

Authors: Hiromitsu Takeuchi and Makoto Tsubota

Comments: 4 pages, 4 figures

Subj-class: Other

Journal-ref: J. Phys. Soc. Jpn. 75. 063601 (2006)

\\

A boojum is a topological defect that can form only on the surface of an

ordered medium such as superfluid $^3$He and liquid crystals. We study

theoretically boojums appearing between two phases with different vortex

structures in two-component BECs where the intracomponent interaction is

repulsive in one phase and attractive in the other. The detailed structure of

the boojums is revealed by investigating its density distribution, effective

superflow vorticity and pseudospin texture.

\\ ( http://arXiv.org/abs/cond-mat/0606684 , 319kb)

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Paper: cond-mat/0606697

Date: Tue, 27 Jun 2006 14:59:14 GMT (266kb)

Title: Fermionic atoms trapped in one-dimensional optical superlattice with

harmonic confinement

Authors: Takanori Yamashita, Norio Kawakami, Makoto Yamashita

Comments: 7 pages, 7 figures

Subj-class: Statistical Mechanics

\\

We study the ground-state properties of spin-1/2 fermionic atoms confined in

a one-dimensional optical superlattice with harmonic confinement by using the

density matrix renormalization group method. For this purpose, we consider an

ionic Hubbard model that has superlattice potentials with 2-site periodicity.

We find that several different types of insulating regimes coexist even if the

number of atoms at each site is not an integer, but its average within the unit

cell is an integer or half integer. This is contrasted to the coexisting phase

of the metallic and Mott-insulating regimes known for the ordinary Hubbard

model in an optical lattice. The phase characteristics are elucidated by

investigating the profiles of the atom density, the local density/spin

fluctuations, the double occupation probability and the spin correlations in

detail.

\\ ( http://arXiv.org/abs/cond-mat/0606697 , 266kb)

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Paper: cond-mat/0506034

replaced with revised version Tue, 27 Jun 2006 15:19:58 GMT (66kb)

Title: Weakly Interacting, Dilute Bose Gases in 2D

Authors: Anna Posazhennikova

Comments: Survey, 25 pages RMP style, revised version, refs added, some changes

made, accepted for publication in Rev. Mod. Phys

Subj-class: Other; Statistical Mechanics

\\ ( http://arXiv.org/abs/cond-mat/0506034 , 66kb)

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Paper: cond-mat/0511347

replaced with revised version Tue, 27 Jun 2006 13:22:21 GMT (173kb)

Title: Dynamics of the Bose-Einstein condensation: analogy with the collapse

dynamics of a classical self-gravitating Brownian gas

Authors: Julien Sopik, Clement Sire and Pierre-Henri Chavanis

Subj-class: Statistical Mechanics

\\ ( http://arXiv.org/abs/cond-mat/0511347 , 173kb)

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Paper: cond-mat/0606706

Date: Wed, 28 Jun 2006 05:38:23 GMT (92kb)

Title: Superfluidity and non-monogamous pairing at unitarity

Authors: Dean Lee (North Carolina State University)

Comments: 43 pages, 25 figures

Subj-class: Statistical Mechanics; Superconductivity

\\

We present lattice results for spin-1/2 fermions at unitarity, where the

effective range of the interaction is zero and the scattering length is

infinite. We measure the spatial coherence of difermion pairs for a system of

6, 10, 14, 18, 22, 26 particles with equal numbers of up and down spins in a

periodic cube. Using Euclidean time projection, we analyze ground state

properties and transient behavior due to low-energy excitations. The results

indicate a low-energy excitation consistent with two quasiparticles moving in

opposite directions at approximately 0.8 times the Fermi momentum. However the

excitation lies well below twice the pairing gap estimated from even-odd ground

state energy staggering and couples strongly to the difermion order parameter.

In order to explain this we develop a theoretical framework for non-monogamous

pairing and an interpretation of the two-quasiparticle excitation as two

countermoving half rotons.

\\ ( http://arXiv.org/abs/cond-mat/0606706 , 92kb)

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Paper: cond-mat/0606709

Date: Wed, 28 Jun 2006 00:03:39 GMT (123kb)

Title: Absence of Fragmentation in Two-Dimensional Bose-Einstein Condensation

Authors: Juan Pablo Fern\'andez and William J. Mullin

Comments: 6 pages, 1 figure

Subj-class: Statistical Mechanics

Journal-ref: J. Low Temp. Phys. 138, 687 (2005)

\\

We investigate the possibility that the BEC-like phenomena recently detected

on two-dimensional finite trapped systems consist of fragmented condensates. We

derive and diagonalize the one-body density matrix of a two-dimensional

isotropically trapped Bose gas at finite temperature. For the ideal gas, the

procedure reproduces the exact harmonic-oscillator eigenfunctions and the Bose

distribution. We use a new collocation-minimization method to study the

interacting gas in the Hartree-Fock approximation and obtain a ground-state

wavefunction and condensate fraction consistent with those obtained by other

methods. The populations of the next few eigenstates increase at the expense of

the ground state but continue to be negligible; this supports the conclusion

that two-dimensional BEC is into a single state.

\\ ( http://arXiv.org/abs/cond-mat/0606709 , 123kb)

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Paper: cond-mat/0606710

Date: Wed, 28 Jun 2006 00:15:27 GMT (169kb)

Title: Path-integral Monte Carlo and the squeezed trapped Bose-Einstein gas

Authors: Juan Pablo Fern\'andez and William J. Mullin

Comments: 2 pages, 3 figures

Subj-class: Statistical Mechanics

\\

Bose-Einstein condensation has been experimentally found to take place in

finite trapped systems when one of the confining frequencies is increased until

the gas becomes effectively two-dimensional (2D). We confirm the plausibility

of this result by performing path-integral Monte Carlo (PIMC) simulations of

trapped Bose gases of increasing anisotropy and comparing them to the

predictions of finite-temperature many-body theory. PIMC simulations provide an

essentially exact description of these systems; they yield the density profile

directly and provide two different estimates for the condensate fraction. For

the ideal gas, we find that the PIMC column density of the squeezed gas

corresponds quite accurately to that of the exact analytic solution and,

moreover, is well mimicked by the density of a 2D gas at the same temperature;

the two estimates for the condensate fraction bracket the exact result. For the

interacting case, we find 2D Hartree-Fock solutions whose density profiles

coincide quite well with the PIMC column densities and whose predictions for

the condensate fraction are again bracketed by the PIMC estimates.

\\ ( http://arXiv.org/abs/cond-mat/0606710 , 169kb)

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Paper: cond-mat/0605048

replaced with revised version Wed, 28 Jun 2006 06:37:21 GMT (182kb)

Title: Deviation from one-dimensionality in stationary properties and

collisional dynamics of matter-wave solitons

Authors: Lev Khaykovich, Boris A. Malomed

Comments: 10 pages, 7 figures

Subj-class: Other

\\ ( http://arXiv.org/abs/cond-mat/0605048 , 182kb)

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Paper: quant-ph/0606233

Date: Wed, 28 Jun 2006 12:21:01 GMT (129kb)

Title: Collective Two-Atom Effects and Trapping States in the Micromaser

Authors: Per K. Rekdal and Bo-Sture K. Skagerstam

Comments: 5 figures

\\

We investigate signals of trapping states in the micromaser system in terms

of the average number of cavity photons as well as a suitably defined

correlation length of atoms leaving the cavity. In the description of

collective two-atom effects we allow the mean number of pump atoms inside the

cavity during the characteristic atomic cavity transit time to be as large as

of order one. The master equation we consider, which describes the micromaser

including collective two-atom effects, still exhibits trapping states for even

for a mean number of atoms inside the cavity close to one. We, however, argue

more importantly that the trapping states are more pronounced in terms of the

correlation length as compared to the average number of cavity photons, i.e. we

suggest that trapping states can be more clearly revealed experimentally in

terms of the atom correlation length. For axion detection in the micromaser

this observable may therefore be an essential ingredient.

\\ ( http://arXiv.org/abs/quant-ph/0606233 , 129kb)

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Paper: quant-ph/0606234

Date: Wed, 28 Jun 2006 14:08:56 GMT (291kb)

Title: Experimental Observation of Four-Photon Entangled Dicke State with High

Fidelity

Authors: Nikolai Kiesel, Christian Schmid, Geza Toth, Enrique Solano, and

Harald Weinfurter

Comments: 5 pages, 3 figures, submitted

\\

We present the experimental observation of the symmetric four-photon

entangled Dicke state with two excitations $|D_{4}^{(2)}>$. A simple

experimental set-up allowed quantum state tomography yielding a fidelity as

high as $0.844 \pm 0.008$. We study the entanglement persistency of the state

using novel witness operators and focus on the demonstration of a remarkable

property: depending on the orientation of a measurement on one photon, the

remaining three photons are projected into both inequivalent classes of genuine

tripartite entanglement, the GHZ and W class. Furthermore, we discuss possible

applications of $|D_{4}^{(2)}>$ in quantum communication.

\\ ( http://arXiv.org/abs/quant-ph/0606234 , 291kb)

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Paper (*cross-listing*): quant-ph/0507090

Date: Sat, 9 Jul 2005 04:42:22 GMT (147kb)

Date (revised v2): Mon, 25 Jul 2005 18:41:25 GMT (147kb)

Title: On the unique possibility to increase significantly the contrast of

dark resonances on D1 line of $^{87}$Rb

Authors: A.V. Taichenachev, V.I. Yudin, V.L. Velichansky, and S.A. Zibrov

Categories: quant-ph

Comments: 9 pages, 7 figures. This material has been partially presented on

ICONO-2005, 14 May 2005, St. Petersburg, Russia. v2 references added; text is

changed a bit

Subj-class: Quantum Physics; Atomic Physics

\\

We propose and study, theoretically and experimentally, a new scheme of

excitation of a coherent population trapping resonance for D1 line of alakli

atoms with nuclear spin $I=3/2$ by bichromatic linearly polarized light ({\em

lin}$||${\em lin} field) at the conditions of spectral resolution of the

excited state. The unique properties of this scheme result in a high contrast

of dark resonance for D1 line of $^{87}$Rb.

\\ ( http://arXiv.org/abs/quant-ph/0507090 , 147kb)

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Paper: cond-mat/0606743

Date: Thu, 29 Jun 2006 03:37:03 GMT (19kb)

Title: Predicted quantum stripe ordering in optical lattices

Authors: Congjun Wu, W. Vincent Liu, Joel Moore, and Sankar Das Sarma

Comments: 5 pages, two figures

Subj-class: Strongly Correlated Electrons; Superconductivity

\\

We predict the robust existence of a novel quantum orbital stripe order in

the $p$-band Bose-Hubbard model of two-dimensional triangular optical lattices

with cold bosonic atoms. An orbital angular momentum moment is formed on each

site exhibiting a stripe order both in the superfluid and Mott-insulating

phases. The stripe order spontaneously breaks time-reversal, lattice

translation and rotation symmetries. In addition, it induces staggered

plaquette bond currents in the superfluid phase. Possible signatures of this

stripe order in the time of flight experiment are discussed.

\\ ( http://arXiv.org/abs/cond-mat/0606743 , 19kb)

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Paper: cond-mat/0606755

Date: Thu, 29 Jun 2006 08:45:49 GMT (96kb)

Title: The Goldstone mode of planar optical parametric oscillators

Authors: Michiel Wouters and Iacopo Carusotto

Subj-class: Other

\\

We propose an experimental setup to probe the low-lying excitation modes of a

parametrically oscillating planar cavity, in particular the soft Goldstone mode

which appears as a consequence of the spontaneously broken U(1) symmetry of

signal/idler phase rotations. Differently from the case of thermodynamical

equilibrium, the Goldstone mode of such a driven-dissipative system is an

overdamped mode, whose linewidth goes to zero in the long-wavelength limit.

When the phase of the signal/idler emission is pinned by an additional laser

beam in the vicinity of the signal emission, the U(1) symmetry is explicitely

broken and a gap opens in the Goldstone mode dispersion. This results in a

dramatic broadening of the response to the probe. Quantitative predictions are

given for the case of semiconductor planar cavities in the strong

exciton-photon coupling regime.

\\ ( http://arXiv.org/abs/cond-mat/0606755 , 96kb)

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Paper: cond-mat/0606757

Date: Thu, 29 Jun 2006 09:16:41 GMT (64kb)

Title: Control of the interaction in a Fermi-Bose mixture

Authors: M. Zaccanti, C. D'Errico, F. Ferlaino, G.Roati, M. Inguscio, G.

Modugno

Comments: 5 Pages

Subj-class: Other

\\

We control the interspecies interaction in a two-species atomic quantum

mixture by tuning the magnetic field at a Feshbach resonance. The mixture is

composed by fermionic 40K and bosonic 87Rb. We observe effects of the large

attractive and repulsive interaction energy across the resonance, such as

collapse and spatial separation of the mixture, which we use to accurately

locate the resonance position. Understanding and controlling instabilities in

this mixture opens the way to a variety of applications, including formation of

heteronuclear molecular quantum gases.

\\ ( http://arXiv.org/abs/cond-mat/0606757 , 64kb)

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Paper: cond-mat/0606771

Date: Thu, 29 Jun 2006 14:48:20 GMT (2669kb)

Title: Ultracold atomic gases in optical lattices: Mimicking condensed matter

physics and beyond

Authors: Maciej Lewenstein, Anna Sanpera, Veronica Ahufinger, Bogdan Damski,

Aditi Sen De, Ujjwal Sen

Comments: Review article, submitted to Advances in Physics; 127 pages, 35

figures

Report-no: LAUR-06-4002

Subj-class: Other

\\

We review recent developments in the physics of ultracold atomic and

molecular gases in optical lattices. Such systems are nearly perfect

realisations of various kinds of Hubbard models, and as such may very well

serve to mimic condensed matter phenomena. We show how these systems may be

employed as quantum simulators to answer some challenging open questions of

condensed matter, and even high energy physics. After a short presentation of

the methods of treatment of such systems, we discuss in detail, which

challenges of condensed matter physics can be addressed with (i) disordered

ultracold lattice gases, (ii) frustrated ultracold gases, (iii) spinor lattice

gases, (iv) lattice gases in "artificial" magnetic fields, and, last but not

least, (v) quantum information processing in lattice gases.

\\ ( http://arXiv.org/abs/cond-mat/0606771 , 2669kb)

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Paper (*cross-listing*): math-ph/0606058

Date: Fri, 23 Jun 2006 10:25:44 GMT (24kb)

Title: Rapidly Rotating Bose-Einstein Condensates in Strongly Anharmonic Traps

Authors: M. Correggi, T. Rindler-Daller, J. Yngvason

Comments: LaTex2e,26 pages

Subj-class: Mathematical Physics; Statistical Mechanics

\\

We study a rotating Bose-Einstein Condensate in a strongly anharmonic trap

(flat trap with a finite radius) in the framework of 2D Gross-Pitaevskii

theory. We write the coupling constant for the interactions between the gas

atoms as $1/\epsilon^2$ and we are interested in the limit $\epsilon\to 0$ (TF

limit) with the angular velocity $\Omega$ depending on $\epsilon$. We derive

rigorously the leading asymptotics of the ground state energy and the density

profile when $\Omega$ tends to infinity as a power of $1/\epsilon$. If

$\Omega(\epsilon)=\Omega_0/\epsilon$ a ``hole'' (i.e., a region where the

density becomes exponentially small as $1/\epsilon\to\infty$) develops for

$\Omega_0$ above a certain critical value. If $\Omega(\epsilon)\gg 1/\epsilon$

the hole essentially exhausts the container and a ``giant vortex'' develops

with the density concentrated in a thin layer at the boundary.

\\ ( http://arXiv.org/abs/math-ph/0606058 , 24kb)

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Paper: cond-mat/0605143

replaced with revised version Thu, 29 Jun 2006 14:15:25 GMT (68kb)

Title: Classification of zero-energy resonances by dissociation of Feshbach

molecules

Authors: Thomas M. Hanna, Krzysztof Goral, Emilia Witkowska, Thorsten Koehler

Comments: 10 pages, 5 eps figures

Subj-class: Other

\\ ( http://arXiv.org/abs/cond-mat/0605143 , 68kb)

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Paper: physics/0606249

Date: Wed, 28 Jun 2006 21:05:50 GMT (8kb)

Title: Frequency shift of cesium clock transition due to blackbody radiation

Authors: E. J. Angstmann, V. A. Dzuba and V. V. Flambaum

Comments: Accepted for publication in Phys. Rev. Lett

Subj-class: Atomic Physics

\\

We have performed ab initio calculations of the frequency shift induced by a

static electric field on the cesium clock hyperfine transition. The

calculations are used to find the frequency shifts due to blackbody radiation.

Our result ($\delta \nu/E^2=-2.26(2)\times 10^{-10}$Hz/(V/m)$^2$) is in good

agreement with early measurements and ab initio calculations performed in other

groups. We present arguments against recent claims that the actual value of the

effect might be smaller. The difference ($\sim$ 10%) between ab initio and

semiempirical calculations is due to the contribution of the continuum spectrum

to the sum over intermediate states.

\\ ( http://arXiv.org/abs/physics/0606249 , 8kb)

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Paper: physics/0606214

replaced with revised version Thu, 29 Jun 2006 12:53:35 GMT (89kb)

Title: Optical Lattice Polarization Effects on Hyperpolarizability of Atomic

Clock Transitions

Authors: A. V. Taichenachev and V. I. Yudin, V. D. Ovsiannikov, V. G.

Pal'chikov

Comments: 4 pages, RevTeX4, 2 eps figs

Subj-class: Atomic Physics; Optics

\\ ( http://arXiv.org/abs/physics/0606214 , 89kb)

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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/ ========================================================================= 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 Mon Jul 03 2006 - 10:03:57 EST

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