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

Date: Sun, 27 Jan 2008 22:13:27 +1000

Date: Sun, 27 Jan 2008 22:13:27 +1000

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

Hi everyone,

A large email this week, with 32 new preprints and 16 replacements.

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arXiv:0801.1732

Date: Fri, 11 Jan 2008 08:37:46 GMT (109kb)

Title: Three-Body Recombination of Identical Bosons with a Large Positive

Scattering Length at Nonzero Temperature

Authors: Eric Braaten, H.-W. Hammer, Daekyoung Kang, Lucas Platter

Categories: cond-mat.other

Comments: 34 pages, 10 figures

Report-no: HISKP-TH-08-01

\\

For identical bosons with a large scattering length, the dependence of the

3-body recombination rate on the collision energy is determined by universal

functions of a single scaling variable. There are six scaling functions for

angular momentum zero and one scaling function for each higher partial wave. We

calculate these universal functions by solving the Skorniakov--Ter-Martirosian

equation. The results for the 3-body recombination as a function of the

collision energy are in good agreement with previous results from solving the

3-body Schroedinger equation for He-4 atoms. The universal scaling functions

can be used to calculate the 3-body recombination rate at nonzero temperature.

We obtain an excellent fit to the data from the Innsbruck group for Cs-133

atoms with a large positive scattering length.

\\ ( http://arxiv.org/abs/0801.1732 , 109kb)

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arXiv:0801.1743

Date: Fri, 11 Jan 2008 19:00:34 GMT (497kb)

Title: Temperature Effects in a Fermi Gas with Population Imbalance

Authors: Heron Caldas, and A. L. Mota

Categories: cond-mat.str-el cond-mat.supr-con

Comments: 6 pages, 10 figures

\\

We investigate temperature effects in a Fermi gas with imbalanced spin

populations. From the general expression of the thermal gap equation we find,

in {\it weak coupling limit}, an analytical expression for the transition

temperature $T_c$ as a function of various possibilities of chemical potential

and mass asymmetries between the two particle species. For a range of asymmetry

between certain specific values, this equation always has two solutions for

$T_c$ which has been interpreted as a reentrant phenomena or a pairing induced

by temperature effect. We show that the lower $T_c$ is never related to a

stable solution. The same results are obtained in {\it strong coupling limit}.

The thermodynamical potential is carefully analyzed to avoid the consideration

of the unstable solutions.

\\ ( http://arxiv.org/abs/0801.1743 , 497kb)

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arXiv:0801.1753

Date: Fri, 11 Jan 2008 10:57:49 GMT (269kb)

Title: Path Integral Ground State study of 2D solid 4He

Authors: E. Vitali, M. Rossi, F. Tramonto, D.E. Galli, L. Reatto

Categories: cond-mat.other cond-mat.stat-mech

Comments: 4 pages, 4 figures

\\

We have studied a two-dimensional triangular commensurate crystal of 4He with

the exact T=0 K Path Integral Ground State (PIGS) Monte Carlo method. We have

projected onto the true ground state both a Jastrow-Nosanow wave function, in

which equilibrium positions are explicitly given and no Bose-Einstein (BEC) is

present, and a translationally invariant shadow wave function, in which the

solid phase emerges through a spontaneously broken symmetry process and it has

BEC. We find a remarkable convergence to the same properties, both the diagonal

ones as well as the off-diagonal one-body density matrix rho_1. This supplies a

strong evidence that no variational bias are present in the PIGS method. We

find no BEC in the commensurate 2D 4He crystal at T=0 K, rho_1 shows an

exponential decay in the large distance range. The structure found in rho_1 is

due to virtual vacancy--interstitial pairs and this shows up in the momentum

distribution.

\\ ( http://arxiv.org/abs/0801.1753 , 269kb)

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arXiv:0801.1765

Date: Fri, 11 Jan 2008 12:18:09 GMT (74kb)

Title: The ALPS project release 1.3: open source software for strongly

correlated systems

Authors: A.F. Albuquerque, F. Alet, P. Corboz, P. Dayal, A. Feiguin, S. Fuchs,

L. Gamper, E. Gull, S. Guertler, A. Honecker, R. Igarashi, M. Koerner, A.

Kozhevnikov, A. Laeuchli, S.R. Manmana, M. Matsumoto, I.P. McCulloch, F.

Michel, R.M. Noack, G. Pawlowski, L. Pollet, T. Pruschke, U. Schollwock, S.

Todo, S. Trebst, M. Troyer, P. Werner, S. Wessel (for the ALPS collaboration)

Categories: cond-mat.str-el cond-mat.stat-mech

Journal-ref: Journal of Magnetism and Magnetic Materials 310, 1187 (2007)

DOI: 10.1016/j.jmmm.2006.10.304

\\

We present release 1.3 of the ALPS (Algorithms and Libraries for Physics

Simulations) project, an international open source software project to develop

libraries and application programs for the simulation of strongly correlated

quantum lattice models such as quantum magnets, lattice bosons, and strongly

correlated fermion systems. Development is centered on common XML and binary

data formats, on libraries to simplify and speed up code development, and on

full-featured simulation programs. The programs enable non-experts to start

carrying out numerical simulations by providing basic implementations of the

important algorithms for quantum lattice models: classical and quantum Monte

Carlo (QMC) using non-local updates, extended ensemble simulations, exact and

full diagonalization (ED), as well as the density matrix renormalization group

(DMRG). Changes in the new release include a DMRG program for interacting

models, support for translation symmetries in the diagonalization programs, the

ability to define custom measurement operators, and support for inhomogeneous

systems, such as lattice models with traps. The software is available from our

web server at http://alps.comp-phys.org/ .

\\ ( http://arxiv.org/abs/0801.1765 , 74kb)

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arXiv:0801.1815

Date: Fri, 11 Jan 2008 18:06:13 GMT (38kb)

Title: Superfluid pairing between fermions with unequal masses

Authors: M.A. Baranov, C. Lobo, and G.V. Shlyapnikov

Categories: cond-mat.other cond-mat.supr-con

Comments: 20 pages, 9 figures

\\

We consider a superfluid state in a two-component gas of fermionic atoms with

equal densities and unequal masses in the BCS limit. We develop a perturbation

theory along the lines proposed by Gorkov and Melik-Barkhudarov and find that

for a large difference in the masses of heavy ($M$) and light ($m$) atoms one

has to take into account both the second-order and third-order contributions.

The result for the critical temperature and order parameter is then quite

different from the prediction of the simple BCS approach. Moreover, the small

parameter of the theory turns out to be $(p_{F}|a|)/\hbar)\sqrt{M/m}\ll1$,

where $p_{F}$ is the Fermi momentum, and $a$ the scattering length. Thus, for a

large mass ratio $M/m$ the conventional perturbation theory requires

significantly smaller Fermi momenta (densities) or scattering lengths than in

the case of $M\sim m$, where the small parameter is $(p_{F}|a|)/\hbar)\ll1$. We

show that 3-body scattering resonances appearing at a large mass ratio due to

the presence of 3-body bound Efimov states do not influence the result, which

in this sense becomes universal.

\\ ( http://arxiv.org/abs/0801.1815 , 38kb)

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arXiv:0801.1837

Date: Fri, 11 Jan 2008 20:53:44 GMT (10kb)

Title: A test of the g-ology model for one-dimensional interacting Fermi

systems

Authors: Andrey V. Chubukov, Dmitrii L. Maslov, and Fabian H.L. Essler

Categories: cond-mat.str-el

Comments: 4 pp, 1 fig, submitted to PRB RC

\\

Bosonization predicts that the specific heat, C(T), of a one-dimensional

interacting Fermi system is a sum of the specific heats of free collective

charge and spin excitations, plus the term with the running backscattering

amplitude which flows to zero logarithmically with decreasing T. We verify

whether this result is reproduced in the g-ology model. Of specific interest

are the anomalous terms in C(T) that depend on the bare backscattering

amplitude. We show that these terms can be incorporated into a renormalized

spin velocity. We do this by proving the equivalence of the results for C(T)

obtained within the g-ology model and by bosonization with velocities obtained

by the numerical solution of the Bethe-ansatz equations for the Hubbard model.

\\ ( http://arxiv.org/abs/0801.1837 , 10kb)

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arXiv:0801.1887

Date: Mon, 14 Jan 2008 19:25:48 GMT (120kb)

Title: Temperature changes when adiabatically ramping up an optical lattice

Authors: Lode Pollet, Corinna Kollath, Kris Van Houcke, Matthias Troyer

Categories: cond-mat.stat-mech

Comments: 18 pages, 24 figure

\\

When atoms are loaded into an optical lattice, the process of gradually

turning on the lattice is almost adiabatic. In this paper we investigate how

the temperature changes when going from the gapless superfluid phase to the

gapped Mott phase along isentropic lines. To do so we calculate the entropy in

the single-band Bose-Hubbard model for various densities, interaction strengths

and temperatures in one and two dimensions for homogeneous and trapped systems.

Our theory is able to reproduce the experimentally observed visibilities and

therefore strongly supports that current experiments remain in the quantum

regime for all considered lattice depths with low temperatures and minimal

heating.

\\ ( http://arxiv.org/abs/0801.1887 , 120kb)

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arXiv:0801.1916

Date: Sat, 12 Jan 2008 19:14:41 GMT (438kb)

Title: Quantised Vortices in an Exciton-Polariton Fluid

Authors: K. G. Lagoudakis, M. Wouters, M. Richard, A. Baas, I. Carusotto, R.

Andre, Le Si Dang, B. Deveaud-Pledran

Categories: cond-mat.other

Comments: 14 pages, 4 figures

\\

One of the most striking quantum effects in a low temperature interacting

Bose gas is superfluidity. First observed in liquid 4He, this phenomenon has

been intensively studied in a variety of systems for its amazing features such

as the persistence of superflows and the quantization of the angular momentum

of vortices. The achievement of Bose-Einstein condensation (BEC) in dilute

atomic gases provided an exceptional opportunity to observe and study

superfluidity in an extremely clean and controlled environment. In the solid

state, Bose-Einstein condensation of exciton polaritons has now been reported

several times. Polaritons are strongly interacting light-matter

quasi-particles, naturally occurring in semiconductor microcavities in the

strong coupling regime and constitute a very interesting example of composite

bosons. Even though pioneering experiments have recently addressed the

propagation of a fluid of coherent polaritons, still no conclusive evidence is

yet available of its superfluid nature. In the present Letter, we report the

observation of spontaneous formation of pinned quantised vortices in the

Bose-condensed phase of a polariton fluid by means of phase and amplitude

imaging. Theoretical insight into the possible origin of such vortices is

presented in terms of a generalised Gross-Pitaevskii equation. The implications

of our observations concerning the superfluid nature of the non-equilibrium

polariton fluid are finally discussed.

\\ ( http://arxiv.org/abs/0801.1916 , 438kb)

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arXiv:0801.1947

Date: Sun, 13 Jan 2008 11:08:46 GMT (431kb)

Title: Improved Scaling for Periodic Matrix Product State Algorithms

Authors: Peter Pippan, Steven R. White, and Hans Gerd Evertz

Categories: cond-mat.str-el

\\

Recently, Verstraete et. al. proposed a matrix product state (MPS)

variational method for one dimensional systems with periodic boundary

conditions, for which the density matrix renormalization group (DMRG) does not

converge well. However, as Verstraete et. al. pointed out, while the dimension

m of the matrices could be made much smaller than in DMRG, the calculation time

scaled as m5 rather than m3. We modify the MPS method and we introduce a

factorization procedure which reduces the calculation time to m3, making MPS

calculations with periodic boundary conditions comparable in efficiency to DMRG

with open boundaries. We test the method on the S=1/2 and S=1 Heisenberg

chains. It is also applicable to non-translationally invariant cases.

\\ ( http://arxiv.org/abs/0801.1947 , 431kb)

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arXiv:0801.2002

Date: Mon, 14 Jan 2008 02:25:13 GMT (609kb)

Title: Efimov states embedded in the three-body continuum

Authors: N. P. Mehta, Seth T. Rittenhouse, J. P. D'Incao, Chris H. Greene

Categories: cond-mat.other

Comments: 4 pages 3 figures

\\

We consider a multichannel generalization of the Fermi pseudopotential to

model low-energy atom-atom interactions near a magnetically tunable Feshbach

resonance, and calculate the adiabatic hyperspherical potential curves for a

system of three such interacting atoms. In particular, our model suggests the

existence of a series of quasi-bound Efimov states attached to excited

three-body thresholds, far above open channel collision energies. We discuss

the conditions under which such states may be supported, and identify which

interaction parameters limit the lifetime of these states. We speculate that it

may be possible to observe these states using spectroscopic methods, perhaps

allowing for the measurement of multiple Efimov resonances for the first time.

\\ ( http://arxiv.org/abs/0801.2002 , 609kb)

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arXiv:0801.2056

Date: Mon, 14 Jan 2008 12:06:09 GMT (205kb)

Title: Double and negative reflection of cold atoms in non-Abelian gauge

potentials

Authors: Gediminas Juzeliunas, Julius Ruseckas, Andreas Jacob, Luis Santos,

Patrik Ohberg

Categories: cond-mat.other

Comments: 5 figures

\\

Atom reflection is studied in the presence of a non-Abelian vector potential

proportional to a spin-1/2 operator. The potential is produced by a relatively

simple laser configuration for atoms with a tripod level scheme. We show that

the atomic motion is described by two different dispersion branches with

positive or negative chirality. As a consequence of that, atom reflection shows

unusual features, since an incident wave may split into two reflected ones at a

barrier, an ordinary specular reflection, and an additional non-specular one.

Remarkably, the latter wave can exhibit negative reflection and may become

evanescent if the angle of incidence exceeds a critical value. These reflection

properties are crucial for future designs in non-Abelian atom optics.

\\ ( http://arxiv.org/abs/0801.2056 , 205kb)

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arXiv:0801.2078

Date: Mon, 14 Jan 2008 14:02:33 GMT (11kb)

Title: On entropy growth and the hardness of simulating time evolution

Authors: Norbert Schuch, Michael M. Wolf, Karl Gerd H. Vollbrecht, J. Ignacio

Cirac

Categories: quant-ph

Comments: 14 pages

\\

The simulation of quantum systems is a task for which quantum computers are

believed to give an exponential speedup as compared to classical ones. While

ground states of one-dimensional systems can be efficiently approximated using

Matrix Product States (MPS), their time evolution can encode quantum

computations, so that simulating the latter should be hard classically.

However, one might believe that for systems with high enough symmetry, and thus

insufficient parameters to encode a quantum computation, efficient classical

simulation is possible. We discuss supporting evidence to the contrary: We

provide a rigorous proof of the observation that a time independent local

Hamiltonian can yield a linear increase of the entropy when acting on a product

state in a translational invariant framework. This challenges every classical

simulation method and it implies in particular that every global approximation

of the evolution requires exponential resources for any MPS based method.

\\ ( http://arxiv.org/abs/0801.2078 , 11kb)

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arXiv:0801.2324

Date: Tue, 15 Jan 2008 15:18:27 GMT (248kb)

Title: Spin-drag relaxation time in one-dimensional spin-polarized Fermi gases

Authors: Diego Rainis, Marco Polini, M.P. Tosi, and G. Vignale

Categories: cond-mat.str-el

Comments: 7 pages, 5 figures

Journal-ref: Phys. Rev. B 77, 035113 (2008)

DOI: 10.1103/PhysRevB.77.035113

\\

Spin propagation in systems of one-dimensional interacting fermions at finite

temperature is intrinsically diffusive. The spreading rate of a spin packet is

controlled by a transport coefficient termed "spin drag" relaxation time

$\tau_{\rm sd}$. In this paper we present both numerical and analytical

calculations of $\tau_{\rm sd}$ for a two-component spin-polarized cold Fermi

gas trapped inside a tight atomic waveguide. At low temperatures we find an

activation law for $\tau_{\rm sd}$, in agreement with earlier calculations of

Coulomb drag between slightly asymmetric quantum wires, but with a different

and much stronger temperature dependence of the prefactor. Our results provide

a fundamental input for microscopic time-dependent spin-density functional

theory calculations of spin transport in 1D inhomogeneous systems of

interacting fermions.

\\ ( http://arxiv.org/abs/0801.2324 , 248kb)

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arXiv:0801.2337

Date: Tue, 15 Jan 2008 16:58:18 GMT (48kb)

Title: Symbiotic gap and semi-gap solitons in Bose-Einstein condensates

Authors: Sadhan K. Adhikari and Boris A. Malomed

Categories: cond-mat.other

Comments: 5 pages, 9 figures

\\

Using the variational approximation (VA) and numerical simulations, we study

one-dimensional gap solitons in a binary Bose-Einstein condensate trapped in an

optical-lattice potential. We consider the case of inter-species repulsion,

while the intra-species interaction may be either repulsive or attractive.

Several types of gap solitons are found: symmetric or asymmetric; %depending on

numbers of unsplit or split, if centers of the components coincide or separate;

intra-gap (with both chemical potentials falling into a single bandgap) or

inter-gap, otherwise. %We identify In the case of the intra-species attraction,

a smooth transition takes place between solitons in the semi-infinite gap, the

ones in the first finite bandgap, and \textit{semi-gap} solitons (with one

component in a bandgap and the other in the semi-infinite gap).

\\ ( http://arxiv.org/abs/0801.2337 , 48kb)

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arXiv:0801.2343

Date: Tue, 15 Jan 2008 17:21:14 GMT (301kb)

Title: Ultracold bosons in lattices with binary disorder

Authors: K.V.Krutitsky, M.Thorwart, R.Egger, R.Graham

Categories: cond-mat.dis-nn cond-mat.other

\\

Quantum phases of ultracold bosons with repulsive interactions in lattices in

the presence of quenched disorder are investigated. The disorder is assumed to

be caused by the interaction of the bosons with impurity atoms having a large

effective mass. The system is described by the Bose-Hubbard Hamiltonian with

random on-site energies which have a discrete binary probability distribution.

The phase diagram at zero temperature is calculated using several methods like

a strong-coupling expansion, an exact numerical diagonalization, and a

Bose-Fermi mapping valid in the hard-core limit. It is shown that the

Mott-insulator phase exists for any strength of disorder in contrast to the

case of continuous probablity distribution. We find that the compressibility of

the Bose glass phase varies in a wide range and can be extremely low.

Furthermore, we evaluate experimentally accessible quantities like the momentum

distribution, the static and dynamic structure factors and the density of

excited states. The influence of finite temperature is discussed as well.

\\ ( http://arxiv.org/abs/0801.2343 , 301kb)

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arXiv:0801.2364

Date: Tue, 15 Jan 2008 19:08:43 GMT (236kb)

Title: Bright solitary waves in a Bose-Einstein condensate and their

interactions

Authors: K. Karkkainen, A. D. Jackson, G. M. Kavoulakis

Categories: cond-mat.other

Comments: 6 pages, 14 figures

\\

We examine the dynamics of two bright solitary waves with a negative

nonlinear term. The observed repulsion between two solitary waves -- when these

are in an antisymmetric combination -- is attributed to conservation laws.

Slight breaking of parity, in combination with weak relaxation of energy, leads

the two solitary waves to merge. The effective repulsion between solitary waves

requires certain nearly ideal conditions and is thus fragile.

\\ ( http://arxiv.org/abs/0801.2364 , 236kb)

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arXiv:0801.2240

Date: Tue, 15 Jan 2008 09:50:12 GMT (218kb)

Title: High momentum entanglement of cold atoms generated by a single photon

scattering

Authors: Rui Guo, Xiaoji Zhou, Xuzong Chen

Categories: quant-ph

Comments: 4 pages, 5 figures

\\

With the mechanism of pairwise scattering of photons between two atoms, we

propose a novel scheme to highly entangle the motional state between two

ultracold neutral atoms by a single photon scattering and detection. Under

certain conditions, it is shown that an arbitrary amount of entanglement can be

obtained with this scheme.

\\ ( http://arxiv.org/abs/0801.2240 , 218kb)

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arXiv:0801.2223

Date: Tue, 15 Jan 2008 07:13:15 GMT (200kb)

Title: Cloaking of Matter Waves

Authors: Shuang Zhang, Dentcho A. Genov, Cheng Sun and Xiang Zhang

Categories: physics.optics physics.gen-ph

Comments: 14 pages, 3 figs

\\

Invariant transformation for quantum mechanical systems is proposed. A

cloaking of matter wave can be realized at given energy by designing the

potential and effective mass of the matter waves in the cloaking region. The

general conditions required for such a cloaking are determined and confirmed by

both the wave and particle (classical) approaches. We show that it may be

possible to construct such a cloaking system for cold atoms using optical

lattices.

\\ ( http://arxiv.org/abs/0801.2223 , 200kb)

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arXiv:0801.2500

Date: Wed, 16 Jan 2008 05:48:49 GMT (5513kb)

Title: Making, probing and understanding ultracold Fermi gases

Authors: Wolfgang Ketterle and Martin W. Zwierlein

Categories: cond-mat.other cond-mat.str-el

Comments: Long review article, 206 pages, 74 figures, to appear in Ultracold

Fermi Gases, Proceedings of the International School of Physics "Enrico

Fermi", Course CLXIV, Varenna, 20 - 30 June 2006, edited by M. Inguscio, W.

Ketterle, and C. Salomon (IOS Press, Amsterdam) 2008

\\

A review on superfluidity and the BEC-BCS crossover in ultracold Fermi gases.

\\ ( http://arxiv.org/abs/0801.2500 , 5513kb)

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arXiv:0801.2396

Date: Tue, 15 Jan 2008 22:08:40 GMT (25kb)

Title: Many-body dynamics of Rydberg excitation using the $\Omega$-expansion

Authors: J. Stanojevic and R. C\^ot\'e

Categories: quant-ph

Comments: 9 pages, 3 figures, 1 table

\\

We investigate the excitation dynamics of Rydberg atoms in ultracold atomic

samples by expanding the excitation probability and the correlation function

between excited atoms in powers of the isolated atom Rabi frequency $\Omega$.

In the Heisenberg picture, we give recurrence relations to calculate any order

of the expansions, which ere expected to be well-behaved for arbitrarily strong

interactions. For homogeneous large samples, we give the explicit form of the

expansions, up to $\Omega^4$, averaged over all possible random spatial

distributions of atoms, for the most important cases of excitation pulses and

interactions.

\\ ( http://arxiv.org/abs/0801.2396 , 25kb)

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arXiv:0801.2406

Date: Tue, 15 Jan 2008 22:50:12 GMT (21kb)

Title: Many-body Rabi oscillations of Rydberg excitation in small mesoscopic

samples

Authors: J. Stanojevic and R. C\^ot\'e

Categories: quant-ph

Comments: 8 pages, 5 figures

\\

We investigate the collective aspects of Rydberg excitation in ultracold

mesoscopic systems. Strong interactions between Rydberg atoms influence the

excitation process and impose correlations between excited atoms. The

manifestations of the collective behavior of Rydberg excitation are the

many-body Rabi oscillations, spatial correlations between atoms as well as the

fluctuations of the number of excited atoms. We study these phenomena in detail

by numerically solving the many-body Schr\"edinger equation.

\\ ( http://arxiv.org/abs/0801.2406 , 21kb)

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arXiv:0801.2440

Date: Wed, 16 Jan 2008 07:19:21 GMT (216kb)

Title: Subluminal to superluminal propagation of an optical pulse in an

f-deformed Bose- Einstein condensate

Authors: Z. Haghshenasfard, M. H. Naderi and M. Soltanolkotabi

Categories: quant-ph

Comments: 37 pages, 15 figures

\\

In this paper, we investigate the propagation of a weak optical probe pulse

in an f-deformed Bose- Einstein condensate (BEC) of a gas with the -type three-

level atoms in the electromagnetically induced transparency (EIT) regime. We

use an f- deformed generalization of an effective two- level quantum model of

the three- level configuration in which the Gardiner phonon operators for BEC

are deformed by an operator- valued function, f(n), of the particle- number

operator n. With making use of the quantum approach of the angular momentum

theory we obtain the eigenvalues and eigenfunctions of the system up to first

order approximation. We consider the collisions between the atoms as a special

kind of f- deformation. The collision rate k is regarded as the deformation

parameter and light propagation in the deformed BEC is analyzed. In particular,

we show that the absorptive and dispersive properties of the deformed

condensate can be controlled effectively by changing the deformation parameter

k and the total number of atoms. We find that by increasing the value of k the

group velocity of the probe pulse changes, through deformed condensate, from

subluminal to superluminal.

\\ ( http://arxiv.org/abs/0801.2440 , 216kb)

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arXiv:0801.2448

Date: Wed, 16 Jan 2008 08:32:21 GMT (256kb)

Title: Atom cooling with an atom-optical diode on a ring

Authors: A. Ruschhaupt, J. G. Muga

Categories: quant-ph

Comments: 4 pages, 4 figures

\\

We propose a method to cool atoms on a ring by combining an atom diode -a

laser valve for one-way atomic motion which induces robust internal state

excitation- and a trap. We demonstrate numerically that the atom is efficiently

slowed down at each diode crossing, and it is finally trapped when its velocity

is below the trap threshold.

\\ ( http://arxiv.org/abs/0801.2448 , 256kb)

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arXiv:0801.2449

Date: Wed, 16 Jan 2008 08:22:06 GMT (775kb)

Title: Entanglement renormalization in free bosonic systems: real-space versus

momentum-space renormalization group transforms

Authors: G. Evenbly, G. Vidal

Categories: quant-ph

Comments: 13 pages, 9 figures

\\

The ability of entanglement renormalization (ER) to generate a proper

real-space renormalization group (RG) flow in harmonic lattice systems of D=1

and D=2 spatial dimensions is analyzed. A conceptual overview of the steps

involved in momentum-space RG is provided and contrasted against the equivalent

steps in the real-space setting. The real-space RG flow, as generated by ER, is

compared with exact results from momentum space including an investigation of a

critical fixed points and examples with relevant/irrelevant perturbations.

\\ ( http://arxiv.org/abs/0801.2449 , 775kb)

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arXiv:0801.2514

Date: Wed, 16 Jan 2008 16:09:36 GMT (159kb)

Title: Trapping cold Atoms by Quantum Reflection

Authors: Alexander Jurisch, Jan-Michael Rost

Categories: quant-ph

Comments: 10 pages, 7 figures

\\

We examine the properties of a quantum reflection trap when

particle-interaction is included. We explore the influence of the

particle-interaction on the trapping for different regimes: repulsive

particle-interaction and attractive particle-interaction in its stable and

unstable limit. With variational techniques, we calculate the phase-diagram of

the quatum reflection trap and determine the stable and unstable regimes of the

system.

\\ ( http://arxiv.org/abs/0801.2514 , 159kb)

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arXiv:0801.2386

Date: Tue, 15 Jan 2008 21:15:38 GMT (178kb)

Title: Long-range potentials and $(n-1)d+ns$ molecular resonances in an

ultracold rydberg gas

Authors: J. Stanojevic, R. C\^ot\'e, D. Tong, E.E. Eyler, and P.L. Gould

Categories: physics.atom-ph

Comments: 11 pages, 7 figures

\\

We have calculated long-range molecular potentials of the $0_g^{+}$,

$0_u^{-}$ and $1_u$ symmetries between highly-excited rubidium atoms. Strong

$np+np$ potentials characterized by these symmetries are important in

describing interaction-induced phenomena in the excitation spectra of high $np$

Rydberg states. Long-range molecular resonances are such phenomena and they

were first reported in S.M. Farooqi {\it et al.}, Phys. Rev. Lett. {\bf 91}

183002. One class of these resonances occurs at energies corresponding to

excited atom pairs $(n-1)d+ns$. Such resonances are attributed to $\ell$-mixing

due to Rydberg-Rydberg interactions so that otherwise forbidden molecular

transitions become allowed. We calculate molecular potentials in Hund's case

(c), use them to find the resonance lineshape and compare to experimental

results.

\\ ( http://arxiv.org/abs/0801.2386 , 178kb)

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arXiv:0801.2580

Date: Wed, 16 Jan 2008 22:29:12 GMT (434kb,D)

Title: Mean-field stationary state of a Bose gas at a Feshbach resonance

Authors: Andrew Carmichael and Juha Javanainen

Categories: cond-mat.other

\\

We study the steady state of a zero-temperature Bose gas near a Feshbach or

photoassociation resonance using a two-channel mean-field model that

incorporates atomic and molecular condensates, as well as correlated atom pairs

originating from dissociation of molecules into pairs of atoms. We start from a

many-body Hamiltonian for atom-molecule conversion, and derive the time

dependent version of the mean-field theory. The stationary solution of the time

dependent model is rendered unique with an approximation that entails that all

noncondensate atoms are correlated, as if emerging from dissociation of

molecules. The steady state is solved numerically, but limiting cases are also

found analytically. The system has a phase transition in which the atomic

condensate emerges in a nonanalytic fashion. We quantify the scaling of the

observable quantities, such as fractions of atomic and molecular condensates,

with the detuning and the atom-molecule conversion strength. Qualitatively, the

dependence on detuning rounds out with increasing coupling strength. A study of

the thermodynamics shows that the pressure of the atom-molecule system is

negative, even on the molecule side of the resonance. This indicates the

possibility of mechanical instability.

\\ ( http://arxiv.org/abs/0801.2580 , 434kb)

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\\

arXiv:0801.2640

Date: Thu, 17 Jan 2008 10:29:16 GMT (19kb)

Title: Two-component repulsive Fermi gases with population imbalance in

elongated harmonic traps

Authors: M. Colom\'e-Tatch\'e

Categories: cond-mat.str-el

Comments: 4 pages, 3 figures

\\

We study the two-component repulsive Fermi gas with imbalanced populations in

one dimension. Starting from the Bethe Ansatz solution we calculate

analytically the phase diagram for the homogeneous system. We show that two

phases appear: the fully polarised phase and the partially polarised phase. By

means of the local density approximation and the equation of state for the

homogeneous system we calculate the density profile for the harmonically

confined case. We show that a two-shell structure appears: at the center of the

cloud we find the partially polarised phase and at the edges the fully

polarised one. The radii of the inner and outer shells are calculated for

different values of the polarisation and the coupling strength. We calculate

the dependence of the magnetisation on the polarisation for different values of

the coupling strength and we show that the susceptibility is always finite.

\\ ( http://arxiv.org/abs/0801.2640 , 19kb)

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\\

arXiv:0801.2747

Date: Thu, 17 Jan 2008 18:36:49 GMT (218kb)

Title: Energetics and Structural Properties of Trapped Two-Component Fermi

Gases

Authors: J. von Stecher, Chris H. Greene, D. Blume

Categories: cond-mat.other

Comments: 22 pages, 21 figures

\\

Using two different numerical methods, we study the behavior of two-component

Fermi gases interacting through short-range s-wave interactions in a harmonic

trap. A correlated Gaussian basis-set expansion technique is used to determine

the energies and structural properties, i.e., the radial one-body densities and

pair distribution functions, for small systems with either even or odd $N$, as

functions of the s-wave scattering length and the mass ratio $\kappa$ of the

two species. Particular emphasis is put on a discussion of the angular momentum

of the system in the BEC-BCS crossover regime. At unitarity, the excitation

spectrum of the four-particle system with total angular momentum L=0 is

calculated as a function of the mass ratio $\kappa$. The results are analyzed

from a hyperspherical perspective, which offers new insights into the problem.

Additionally, fixed-node diffusion Monte Carlo calculations are performed for

equal-mass Fermi gases with up to N=30 atoms. We focus on the odd-even

oscillations of the ground state energy of the equal-mass unitary system having

up to N=30 particles, which are related to the excitation gap of the system.

Furthermore, we present a detailed analysis of the structural properties of

these systems.

\\ ( http://arxiv.org/abs/0801.2747 , 218kb)

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\\

arXiv:0801.2758

Date: Thu, 17 Jan 2008 20:20:33 GMT (600kb)

Title: Semiclassical theory of the quasi two-dimensional trapped Bose gas

Authors: Markus Holzmann, Maguelonne Chevallier, Werner Krauth

Categories: cond-mat.stat-mech

Comments: 5 pages, 3 figures

\\

We discuss the quasi two-dimensional trapped Bose gas where the thermal

occupation of excited states in the tightly confined direction is small but

remains finite in the thermodynamic limit. We show that the semiclassical

theory describes very accurately the density profile obtained by Quantum Monte

Carlo calculations in the normal phase above the Kosterlitz--Thouless

temperature T_KT, but differs strongly from the predictions of strictly

two-dimensional mean-field theory, even at relatively high temperature. We

discuss the relevance of our findings for analyzing ultra-cold-atom experiments

in quasi two-dimensional traps.

\\ ( http://arxiv.org/abs/0801.2758 , 600kb)

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\\

arXiv:0801.2653

Date: Thu, 17 Jan 2008 11:45:51 GMT (306kb)

Title: Quantum Noise in the Coherent Matter-Wave Displacement Reaction

A+B2->AB+B

Authors: H. Jing, J. Cheng, and P. Meystre

Categories: quant-ph

Comments: 4 pages, 3 figures, submitted

\\

We demonstrate theoretically that the displacement reaction A+B2 ! AB+B

reaction can be realized efficiently with ultracold bosonic or fermionic matter

waves by using a generalized dark-state technique. We show that this reaction

is fundamentally different from the more familiar coherent atom-molecule

conversion (combination/decomposition reaction) in that quantum fluctuations

are critical in triggering its initial stages, with the appearacne of

non-classical correlations of the atomic and molecular fields as a result. This

study opens up a promising new research regime of ultracold matter-wave

superchemistry.

\\ ( http://arxiv.org/abs/0801.2653 , 306kb)

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The replacements:

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\\

arXiv:cond-mat/0703220

replaced with revised version Fri, 11 Jan 2008 11:13:46 GMT (385kb)

Title: Density and Stability in Ultracold Dilute Boson-Fermion Mixtures

Authors: Steffen Roethel and Axel Pelster

Categories: cond-mat.stat-mech

Comments: Author Information under

http://www.theo-phys.uni-essen.de/tp/ags/pelster_dir/

Journal-ref: European Physical Journal B 59, 343 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0703220 , 385kb)

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\\

arXiv:0711.3102

replaced with revised version Fri, 11 Jan 2008 16:29:08 GMT (202kb)

Title: Atom laser dynamics in a tight-waveguide

Authors: A. del Campo, I. Lizuain, M. Pons, J. G. Muga, M. Moshinsky

Categories: cond-mat.other cond-mat.soft

Comments: 6 pages, 5 figures, to be published in the Proceedings of the 395th

WE-Heraeus Seminar on "Time Dependent Phenomena in Quantum Mechanics ",

organized by T. Kramer and M. Kleber (Blaubeuren, Germany, September 2007)

\\ ( http://arxiv.org/abs/0711.3102 , 202kb)

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\\

arXiv:0711.4065

replaced with revised version Fri, 11 Jan 2008 12:47:57 GMT (613kb)

Title: FFLO state in 1, 2, and 3 dimensional optical lattices combined with a

non-uniform background potential

Authors: T.K. Koponen, T. Paananen, J.-P. Martikainen, M.R. Bakhtiari, and P.

Torma

Categories: cond-mat.supr-con cond-mat.str-el

Comments: v2: minor revision, 18 pages, 10 figures

\\ ( http://arxiv.org/abs/0711.4065 , 613kb)

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\\

arXiv:0712.4081

replaced with revised version Fri, 11 Jan 2008 18:29:36 GMT (13kb)

Title: Isospin excitations of a trapped 1D gas of attractively interacting

fermions

Authors: M. Colom\'e-Tatch\'e, G. V. Shlyapnikov and A. M. Tsvelik

Categories: cond-mat.str-el

Comments: 4 pages, 1 figure; minor corrections

\\ ( http://arxiv.org/abs/0712.4081 , 13kb)

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\\

arXiv:0706.3360

replaced with revised version Mon, 14 Jan 2008 14:07:18 GMT (2141kb)

Title: Theory of ultracold Fermi gases

Authors: Stefano Giorgini, Lev P. Pitaevskii, Sandro Stringari

Categories: cond-mat.other

Comments: Revised and abridged version accepted for publication in Rev. Mod.

Phys.: 63 pages, 36 figures

\\ ( http://arxiv.org/abs/0706.3360 , 2141kb)

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\\

arXiv:0708.2667

replaced with revised version Mon, 14 Jan 2008 15:07:46 GMT (196kb)

Title: Migration of bosonic particles across a Mott insulator to superfluid

phase interface

Authors: Michael J. Hartmann and Martin B. Plenio

Categories: cond-mat.str-el cond-mat.stat-mech quant-ph

Comments: 5 pages, 6 figures, to appear in Phys. Rev. Lett

\\ ( http://arxiv.org/abs/0708.2667 , 196kb)

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\\

arXiv:0710.0521

replaced with revised version Mon, 14 Jan 2008 08:39:01 GMT (8kb)

Title: Kinetic Equationins in the Theory of Normal Fermi Liquid

Authors: I. Siddique, A.S. Kondratyev

Categories: cond-mat.stat-mech

\\ ( http://arxiv.org/abs/0710.0521 , 8kb)

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\\

arXiv:0712.2495

replaced with revised version Sat, 12 Jan 2008 01:04:34 GMT (89kb)

Title: On the Quantum Instability of Attractive Bose Systems

Authors: George E. Cragg and Arthur K. Kerman

Categories: cond-mat.other cond-mat.stat-mech

Comments: 60 pages, 6 figures, modified content, added references, corrected

typos

\\ ( http://arxiv.org/abs/0712.2495 , 89kb)

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\\

arXiv:0801.0589

replaced with revised version Fri, 11 Jan 2008 22:31:55 GMT (39kb)

Title: Orbital order in Mott insulators of spinless p-band fermions

Authors: Erhai Zhao and W. Vincent Liu

Categories: cond-mat.str-el cond-mat.other

Comments: added references, corrected Fig.3

\\ ( http://arxiv.org/abs/0801.0589 , 39kb)

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\\

arXiv:0801.1387

replaced with revised version Sat, 12 Jan 2008 13:27:01 GMT (53kb)

Title: Stability of the homogeneous Bose-Einstein condensate at large gas

parameter

Authors: Abdulla Rakhimov, Chul Koo Kim, Sang-Hoon Kim, and Jae Hyung Yee

Categories: cond-mat.stat-mech nucl-th physics.atom-ph

Comments: 9 pages, 3 figures, Revtex

\\ ( http://arxiv.org/abs/0801.1387 , 53kb)

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\\

arXiv:0711.3116

replaced with revised version Mon, 14 Jan 2008 10:03:32 GMT (771kb)

Title: Seeking better times: atomic clocks in the generalized Tonks-Girardeau

regime

Authors: S. V. Mousavi, A. del Campo, I. Lizuain, M. Pons, J. G. Muga

Categories: quant-ph

Comments: Revised manuscript, 8 pages, 8 figures, proceedings of the 395th

WE-Heraeus Seminar on "Time Dependent Phenomena in Quantum Mechanics ",

Blaubeuren, Germany, September 2007

\\ ( http://arxiv.org/abs/0711.3116 , 771kb)

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\\

arXiv:0710.2220

replaced with revised version Tue, 15 Jan 2008 08:39:07 GMT (69kb)

Title: Quantum phases of mixtures of atoms and molecules on optical lattices

Authors: V.G. Rousseau and P.J.H. Denteneer

Categories: cond-mat.stat-mech

Comments: 7 pages, 10 figures

Journal-ref: PRA 77, 013609 (2008)

DOI: 10.1103/PhysRevA.77.013609

\\ ( http://arxiv.org/abs/0710.2220 , 69kb)

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\\

arXiv:0712.2978

replaced with revised version Tue, 15 Jan 2008 13:55:07 GMT (2kb)

Title: Comment on "Atom Interferometers"

Authors: V. A. Kuz'menko

Categories: physics.optics

Comments: 2 pages, other case discussed

\\ ( http://arxiv.org/abs/0712.2978 , 2kb)

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\\

arXiv:0708.0894

replaced with revised version Wed, 16 Jan 2008 07:20:18 GMT (874kb)

Title: Density-Matrix Renormalization Group Study of Trapped Imbalanced Fermi

Condensates

Authors: Masaki Tezuka and Masahito Ueda

Categories: cond-mat.str-el

Comments: 4 pages, 3 figures; revised text; added figures and references

\\ ( http://arxiv.org/abs/0708.0894 , 874kb)

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\\

arXiv:0710.3852

replaced with revised version Wed, 16 Jan 2008 03:59:35 GMT (191kb)

Title: Quantum Antiferromagnetism of Fermions in Optical Lattices with

Half-filled p-band

Authors: Kai Wu and Hui Zhai

Categories: cond-mat.str-el cond-mat.supr-con

Comments: 4 pages,2 figures; Revised version; Discussion on the Neel

temperature expanded

\\ ( http://arxiv.org/abs/0710.3852 , 191kb)

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\\

arXiv:0711.0653

replaced with revised version Wed, 16 Jan 2008 16:48:45 GMT (336kb)

Title: Destroying superfluidity by rotating a Fermi gas at unitarity

Authors: I. Bausmerth, A. Recati, S. Stringari

Categories: cond-mat.soft cond-mat.supr-con

Comments: 5 pages, 4 figures;comments added; 2 figures changed according to new

results; accepted for publication in Physical Review Letters

\\ ( http://arxiv.org/abs/0711.0653 , 336kb)

------------------------------------------------------------------------------

And seeing as you made it this far, have a look at this one for a bit of fun:

------------------------------------------------------------------------------

\\

arXiv:0801.1694

Date: Thu, 10 Jan 2008 23:23:53 GMT (835kb)

Title: Cheap Method for Shielding a City from Rocket and Nuclear Warhead

Impacts

Authors: Alexander Bolonkin

Categories: physics.gen-ph physics.soc-ph

Comments: 31 pages, 11 figures, 4 tables

\\

The author suggests a cheap closed AB-Dome which protects the densely

populated cities from nuclear, chemical, biological weapon (bombs) delivered by

warheads, strategic missiles, rockets, and various incarnations of aviation

technology. The offered AB-Dome is also very useful in peacetime because it

shields a city from exterior weather and creates a fine climate within the

AB-Dome. The hemispherical AB-Dome is the inflatable, thin transparent film,

located at altitude up to as much as 15 km, which converts the city into a

closed-loop system. The film may be armored the stones which destroy the

rockets and nuclear warhead. AB-Dome protects the city in case the World

nuclear war and total poisoning the Earth atmosphere by radioactive fallout

(gases and dust). Construction of the AB-Dome is easy; the enclosure film is

spread upon the ground, the air pump is turned on, and the cover rises to its

planned altitude and supported by a small air over-pressure. The offered method

is cheaper by thousand times than protection of city by current anti-rocket

systems. The AB-Dome may be also used (height up to 15 and more kilometers) for

TV, communication, telescope, long distance location, tourism, high placed

windmills (energy), illumination and entertainments. The author developed

theory of AB-Dome, made estimation, computation and computed a typical project.

Discussion and results are in the end of article.

\\ ( http://arxiv.org/abs/0801.1694 , 835kb)

------------------------------------------------------------------------------

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 Fri Feb 01 2008 - 10:16:26 EST

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