Matt's arXiv selection: week ending 15 August 2008

From: Matthew Davis <>
Date: Fri, 12 Sep 2008 08:32:07 +1000

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

Hello again,

Wow, two mailings in a row! This week there were 18 new preprints and 14

Date: Fri, 8 Aug 2008 15:16:30 GMT (44kb,D)

Title: Range Corrections to Three-Body Observables near a Feshbach Resonance
Authors: Lucas Platter, Chen Ji, Daniel R. Phillips
Categories: cond-mat.other
Comments: 28 pages, 3 figures
   A non-relativistic system of three identical particles will display a rich
set of universal features known as Efimov physics if the scattering length a is
much larger than the range l of the underlying two-body interaction. An
appropriate effective theory facilitates the derivation of both results in the
|a| goes to infinity limit and finite-l/a corrections to observables of
interest. Here we use such an effective-theory treatment to consider the impact
of corrections linear in the two-body effective range, r_s on the three-boson
bound-state spectrum and recombination rate for |a| much greater than |r_s|. We
do this by first deriving results appropriate to the strict limit |a| goes to
infinity in coordinate space. We then extend these results to finite a using
once-subtracted momentum-space integral equations. We also discuss the
implications of our results for experiments that probe three-body recombination
in Bose-Einstein condensates near a Feshbach resonance.
\\ ( , 44kb)
Date: Fri, 8 Aug 2008 19:21:53 GMT (378kb)

Title: Spontaneous recoil effects of optical pumping on trapped atoms
Authors: S. Wallentowitz and P.E. Toschek
Categories: quant-ph
Comments: 21 pages, 6 figures
   The recoil effects of spontaneous photon emissions during optical pumping of
a trapped three-level atom are exactly calculated. Without resort to the
Lamb-Dicke approximation, and considering arbitrary detuning and saturation of
the pump laser, the density of recoil shifts in phase space is derived. It is
shown that this density is not of Gaussian shape, and that it becomes isotropic
in phase space only for a branching ratio corresponding to fluorescence
scattering but unfavorable for optical pumping. The dependence of its
anisotropy on the laser saturation is discussed in the resonant case, and the
mapping of moments of the atom's center-of-mass motion due to the pumping is
presented. Moreover, it is shown how optimum parameters for protecting the
center-of-mass quantum state from pump-induced disturbance depend on the
specific property to be protected.
\\ ( , 378kb)
Date: Fri, 8 Aug 2008 20:24:53 GMT (38kb)

Title: Topological Entropy of 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, the von Neumann entropy is
calculated for the Laughlin and Pfaffian quantum Hall states in rotating
interacting Bose gases at zero temperature in the lowest Landau level limit.
The particles comprising the states are indistinguishable, so the required
spatial bipartitioning is effected by tracing over a subset of single-particle
orbitals. The topological entropy is then extracted through a finite-size
scaling analysis. The results for the Laughlin and the Pfaffian states agree
with the expected values of $\ln\sqrt{2}$ and $\ln\sqrt{4}$, respectively.
\\ ( , 38kb)
Date: Fri, 8 Aug 2008 20:58:11 GMT (67kb,D)

Title: Stability of the fermionic gases close to a p-wave Feshbach resonance
Authors: J. Levinsen, N. R. Cooper, and V. Gurarie
Categories: cond-mat.supr-con cond-mat.other
   We study the stability of the paired fermionic p-wave superfluid made out of
identical atoms all in the same hyperfine state close to a p-wave Feshbach
resonance. First we reproduce known results concerning the lifetime of a 3D
superfluid, in particular, we show that it decays at the same rate as its
interaction energy, thus precluding its equilibration before it decays. Then we
proceed to study its stability in case when the superfluid is confined to 2D by
means of an optical harmonic potential. We find that the relative stability is
somewhat improved in 2D in the BCS regime, such that the decay rate is now
slower than the appropriate interaction energy scale. The improvement in
stability, however, is not dramatic and one probably needs to look for other
mechanisms to suppress decay to create a long lived 2D p-wave fermionic
\\ ( , 67kb)
Date: Sun, 10 Aug 2008 20:45:09 GMT (113kb)

Title: Topological quantum phase transitions of ultracold fermions in optical
Authors: R. W. Cherng, C. A. R. S\'a de Melo
Categories: cond-mat.str-el
Comments: 4 pages, 3 figures
   We consider the possibility of topological quantum phase transitions of
ultracold fermions in optical lattices, which can be studied as a function of
interaction strength or atomic filling factor (density). The phase transitions
are connected to the topology of the elementary excitation spectrum, and occur
only for non-zero angular momentum pairing (p-wave, d-wave and f-wave), while
they are absent for s-wave. We construct phase diagrams for the specific
example of highly anisotropic optical lattices, where the proposed topological
phase transitions are most pronounced. To characterize the existence of these
topological transitions, we calculate several measurable quantities including
momentum distribution, quasi-particle excitation spectrum, atomic
compressibility, superfluid density, and sound velocities.
\\ ( , 113kb)
Date: Mon, 11 Aug 2008 02:45:16 GMT (48kb)

Title: The Asymmetric Superfluid Local Density Approximation (ASLDA)
Authors: Aurel Bulgac, Michael McNeil Forbes
Categories: cond-mat.supr-con cond-mat.other
Comments: 8 pages, RevTeX4, 6 figures
   Here we describe the form of the Asymmetric Superfluid Local Density
Approximation (ASLDA), a Density Functional Theory (DFT) used to model the
two-component unitary Fermi gas. We give the rational behind the functional,
and describe explicitly how we determine the form of the DFT from the to the
available numerical and experimental data.
\\ ( , 48kb)
Date: Mon, 11 Aug 2008 12:14:07 GMT (46kb)

Title: Genuine phase diffusion of a Bose-Einstein condensate in the
   microcanonical ensemble: A classical field study
Authors: Alice Sinatra (LKB - Lhomond), Yvan Castin (LKB - Lhomond)
Categories: cond-mat.other
Comments: 9 pages, 6 figures
   Within the classical field model, we find that the phase of a Bose-Einstein
condensate undergoes a true diffusive motion in the microcanonical ensemble,
the variance of the condensate phase change between time zero and time $t$
growing linearly in $t$. The phase diffusion coefficient obeys a simple scaling
law in the double thermodynamic and Bogoliubov limit. We construct an
approximate calculation of the diffusion coefficient, in fair agreement with
the numerical results over the considered temperature range, and we extend this
approximate calculation to the quantum field.
\\ ( , 46kb)
Date: Mon, 11 Aug 2008 12:33:02 GMT (122kb)

Title: Magnetic dipolar interaction in an atomic Bose Einstein condensate
Authors: M. Fattori, G. Roati, B. Deissler, C. D'Errico, M. Zaccanti, M.
   Jona-Lasinio, L. Santos, M. Inguscio and G. Modugno
Categories: cond-mat.other
Comments: 4 pages, 3 figures
   We study the role played by the magnetic dipole interaction in an atomic
interferometer based on an alkali Bose-Einstein condensate with tunable
scattering length. We tune the s-wave interaction to zero using a magnetic
Feshbach resonance and measure the decoherence of the interferometer induced by
the weak residual interaction between the magnetic dipoles of the atoms. We
prove that with a proper choice of the scattering length it is possible to
compensate for the dipolar interaction and extend the coherence time of the
interferometer. We put in evidence the anisotropic character of the dipolar
interaction by working with two different experimental configurations for which
the minima of decoherence are achieved for a positive and a negative value of
the scattering length, respectively. Our results are supported by a theoretical
model we develop. This model indicates that the magnetic dipole interaction
should not represent a serious source of decoherence in atom interferometers
based on Bose-Einstein condensates.
\\ ( , 122kb)
Date: Mon, 11 Aug 2008 17:53:37 GMT (617kb)

Title: Vortices near the Mott phase of a trapped Bose-Einstein condensate
Authors: Daniel S. Goldbaum, Erich J. Mueller
Categories: cond-mat.other
Comments: Material from arXiv:0807.3609 formatted for journal submission
   We present a theoretical study of vortices within a harmonically trapped
Bose-Einstein condensate in a rotating optical lattice. We find that proximity
to the Mott insulating state dramatically effects the vortex structures. To
illustrate we give examples in which the vortices: (i) all sit at a fixed
distance from the center of the trap, forming a ring, or (ii) coalesce at the
center of the trap, forming a giant vortex. We model time-of-flight expansion
to demonstrate the experimental observability of our predictions.
\\ ( , 617kb)
Date: Tue, 12 Aug 2008 18:34:43 GMT (1531kb)

Title: Raman Coupling of Zeeman Sublevels in an Alkali Bose Condensate
Authors: K. C. Wright, L. S. Leslie, and N. P. Bigelow
Categories: cond-mat.other
Comments: 12 pages, 16 figures
   We investigate amplitude and phase control of the components of the spinor
order parameter of a 87Rb Bose-Einstein condensate. By modeling the interaction
of the multilevel atomic system with a pair of Raman-detuned laser pulses, we
show that it is possible to construct a pulse-sequence protocol for producing a
desired state change within a single Zeeman manifold. We present several
successful elementary tests of this protocol in both the F = 1 and F = 2 Zeeman
manifolds of 87Rb using the D1 transitions. We describe specific features of
the interaction which are important for multimode, spatially-varying field
configurations, including the role of state-dependent, light-induced
\\ ( , 1531kb)
Date: Tue, 12 Aug 2008 12:02:38 GMT (317kb)

Title: Radio-frequency-driven dipole-dipole interactions in spatially separated
Authors: Atreju Tauschinsky, C. S. E. van Ditzhuijzen, L. D. Noordam, H. B. van
   Linden van den Heuvell
Categories: quant-ph
   Radio-frequency (rf) fields in the MHz range are used to induce resonant
energy transfer between cold Rydberg atoms in spatially separated volumes.
After laser preparation of the Rydberg atoms, dipole-dipole coupling at 33 GHz
excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in
the second cylinder are transferred down to the 42p state. The external
rf-field brings this energy transfer into resonance. The strength of this
interaction has been investigated as a function of amplitude and frequency of
the rf-field and as a function of a static field offset. multi-photon
transitions up to fifth order as well as selection rules prohibiting the
process at certain fields have been observed. The width of the resonances has
been reduced compared to earlier results by switching off external magnetic
fields of the magneto-optical trap. All features are well reproduced by
theoretical calculations taking strong the strong ac-Stark shift due to the rf
field into account.
\\ ( , 317kb)
Date: Wed, 13 Aug 2008 05:27:47 GMT (565kb)

Title: Spin-Domain Formation in Antiferromagnetic Condensates
Authors: Michal Matuszewski, Tristram J. Alexander, Yuri S. Kivshar
Categories: cond-mat.other
   Antiferromagnetic condensates are generally believed not to display
modulational instability and subsequent spin-domain formation. Here we
demonstrate that in he presence of a homogeneous magnetic field
antiferromagnetic spin-1 Bose-Einstein condensates can undergo spatial
modulational instability followed by the subsequent generation of spin domains.
Employing numerical simulations for realistic conditions, we show how this
novel effect can be observed in sodium condensates confined in an optical trap.
Finally, we link this instability and spin-domain formation with stationary
modes of the condensate.
\\ ( , 565kb)
Date: Wed, 13 Aug 2008 19:19:09 GMT (240kb)

Title: Hartree-Fock-Bogoliubov Theory of Polarized Fermi Systems
Authors: George Bertsch, Jacek Dobaczewski, Witold Nazarewicz, Junchen Pei
Categories: cond-mat.supr-con nucl-th
Comments: 9 RevTeX pages, 3 figures, submitted to Physical Review A
   Condensed Fermi systems with an odd number of particles can be described by
means of polarizing external fields having a time-odd character. We illustrate
how this works for Fermi gases and atomic nuclei treated by density functional
theory or Hartree-Fock-Bogoliubov (HFB) theory. We demonstrate that by
introducing two chemical potentials for different superfluid components, one
can change the particle-number parity of the underlying quasiparticle vacuum.
Formally, this method is a variant of non-collective cranking, and the
procedure is equivalent to the so-called blocking. Relations between the
two-chemical-potential method and the cranking approximation for Fermi gases
and nuclei are discussed.
\\ ( , 240kb)
Date: Wed, 13 Aug 2008 21:29:06 GMT (37kb)

Title: Fermions with attractive interactions on optical lattices and what they
   imply for correlated systems
Authors: Chih-Chun Chien, Qijin Chen, and K. Levin
Categories: cond-mat.other cond-mat.str-el
Comments: 10 pages, 5 figures
   In this paper we address the behavior of the superfluid transition
temperature $T_c$ in the attractive Hubbard model. We study systematically the
effects of pairing fluctuations and address all filling fractions over the
entire range of attractive interaction strength. While the attractive Hubbard
model can be regarded as the generalization of BCS to Bose Einstein
condensation (BEC) crossover to a lattice, we find that the BEC limit of this
Hubbard model is very different from that of jellium, owing to the strong
inter-site repulsion between pairs, which becomes important near half filling
when the on-site attraction is strong. A central conclusion of our work is that
in a lattice, around half filling, the smooth evolution from the BCS to the BEC
limits is interrupted. For the attractive Hubbard model, $T_c$ vanishes when
the system approaches the bosonic regime with increasing interaction strength.
We suggest that the vanishing of $T_c$ at strong coupling strength may signal a
quantum critical transition to another form of superfluid not continuously
connected to a BCS-like phase. We present a simple variational ansatz for the
ground state in this more strongly coupled superfluid. We further generalize
the (s-wave) Hubbard model to d-wave pairing and address issues of potential
relevance to high temperature superconductors. For the d-wave case, we present
a phase diagram and show that here too, one observes a vanishing of $T_c$ when
the pairing onset temperature $T^*$ becomes sufficiently large. We suggest that
future experiments on ultracold fermions in optical lattices should not be
exclusively limited to the repulsive Hubbard model, but should address the
attractive model in order to elucidate features of high temperature
\\ ( , 37kb)
Date: Thu, 14 Aug 2008 07:58:58 GMT (247kb)

Title: Exact relation between spin squeezing and single-particle coherence in
   two-component Bose-Einstein condensates with Josephson coupling
Authors: G. R. Jin and C. K. Law
Categories: cond-mat.other
Comments: 4 figures, revtex4
   We investigate spin squeezing of a two-mode boson system with a Josephson
coupling. An exact relation between the squeezing and the single-particle
coherence is discovered, which provides an indirect way to measure the
squeezing by readout the coherence in atomic interference experiments. We prove
explicitly that the squeezing is just along the z axis, indicating the
appearance of number-squeezed state. Power laws of the strongest squeezing and
the optimal coupling with particle number $N$ are obtained based upon a wide
range of numerical simulations.
\\ ( , 247kb)
Date: Wed, 13 Aug 2008 20:54:06 GMT (331kb)

Title: Superconducting atom chips: advantages and challenges
Authors: Valery Dikovsky, Vladimir Sokolovsky, Bo Zhang, Carsten Henkel, Ron
Categories: quant-ph
Comments: submitted to Eur. Phys. J. D, latex article class (27 pages, 20 .eps
   figure files)
   Superconductors are considered in view of applications to atom chip devices.
The main features of magnetic traps based on superconducting wires in the
Meissner and mixed states are discussed. The former state may mainly be
interesting for improved atom optics, while in the latter, cold atoms may
provide a probe of superconductor phenomena. The properties of a magnetic side
guide based on a single superconducting strip wire placed in an external
magnetic field are calculated analytically and numerically. In the mixed state
of type II superconductors, inhomogeneous trapped magnetic flux, relaxation
processes and noise caused by vortex motion are posing specific challenges for
atom trapping.
\\ ( , 331kb)
Date: Thu, 14 Aug 2008 17:54:09 GMT (146kb)

Title: Phonon-induced artificial magnetic fields
Authors: Alexander Klein and Dieter Jaksch
Categories: quant-ph
Comments: 6 pages, 4 figures
   We investigate the effect of a rotating Bose-Einstein condensate on a system
of immersed impurity atoms trapped by an optical lattice. We analytically show
that for a one-dimensional, ring-shaped setup the coupling of the impurities to
the Bogoliubov phonons of the condensate leads to a non-trivial phase in the
impurity hopping. The presence of this phase can be tested by observing a drift
in the transport properties of the impurities. These results are quantitatively
confirmed by a numerically exact simulation of a two-mode Bose-Hubbard model.
We also give analytical expressions for the occurring phase terms for a
two-dimensional setup. The phase realises an artificial magnetic field and can
for instance be used for the simulation of the quantum Hall effect using atoms
in an optical lattice.
\\ ( , 146kb)
Date: Thu, 14 Aug 2008 06:36:59 GMT (61kb)

Title: Coherent population trapping in a dressed two-level atom via a
   bichromatic field
Authors: Peng Li, Qun Zhang, Xi-Jing Ning and J. Q. You
Categories: physics.optics physics.atom-ph
Comments: 14 pages, 6 figures
   We show theoretically that by applying a bichromatic electromagnetic field,
the dressed states of a monochromatically driven two-level atom can be pumped
into a coherent superposition termed as dressed-state coherent population
trapping. Such effect can be viewed as a new doorknob to manipulate a two-level
system via its control over dressed-state populations. Application of this
effect in the precision measurement of Rabi frequency, the unexpected
population inversion and lasing without inversion are discussed to demonstrate
such controllability.
\\ ( , 61kb)

The replacements:

replaced with revised version Fri, 8 Aug 2008 10:16:42 GMT (268kb)

Title: Reflection and Refraction of Bose-condensate Excitations
Authors: Shohei Watabe and Yusuke Kato
Categories: cond-mat.other
Comments: 23 pages, 5 figures
\\ ( , 268kb)
replaced with revised version Fri, 8 Aug 2008 14:37:30 GMT (2267kb,D)

Title: Quantum interface between light and atomic ensembles
Authors: K. Hammerer, A.S. Sorensen, E.S. Polzik
Categories: quant-ph cond-mat.other
Comments: 52 pages, 22 figures, submitted to Reviews of Modern Physics;
   corrected references
\\ ( , 2267kb)
replaced with revised version Tue, 5 Aug 2008 07:14:11 GMT (1514kb)

Title: The Physics of Maxwell's demon and information
Authors: Koji Maruyama, Franco Nori, Vlatko Vedral
Categories: physics.hist-ph quant-ph
Comments: 24 pages, 13 figures. v2: some refs added, figs improved
\\ ( , 1514kb)
replaced with revised version Sun, 10 Aug 2008 19:41:13 GMT (68kb)

Title: Proposed realization of itinerant ferromagnetism in optical lattices
Authors: Shizhong Zhang and Congjun Wu
Categories: cond-mat.str-el cond-mat.mtrl-sci
Comments: typos corrected
\\ ( , 68kb)
replaced with revised version Fri, 8 Aug 2008 20:40:55 GMT (108kb)

Title: P-band in a rotating optical lattice
Authors: R.O. Umucalilar, M.O. Oktel
Categories: cond-mat.other
Comments: 7 pages, 4 figures, new discussion of effective Hamiltonian,
   references added
\\ ( , 108kb)
replaced with revised version Sun, 10 Aug 2008 02:28:36 GMT (182kb)

Title: Collective Excitations of Rotating Dipolar Fermi Gases in the Fractional
   Quantum Hall Regime
Authors: Szu-Cheng Cheng
Categories: cond-mat.mes-hall
Comments: 13 pages, 3 figures
\\ ( , 182kb)
replaced with revised version Tue, 12 Aug 2008 13:36:42 GMT (994kb)

Title: The short-range three-body phase and other issues impacting the
   observation of Efimov physics in ultracold quantum gases
Authors: J. P. D'Incao, Chris H. Greene, and B. D. Esry
Categories: cond-mat.other
Comments: 9 pages, 4 figures
\\ ( , 994kb)
replaced with revised version Tue, 12 Aug 2008 02:42:04 GMT (108kb)

Title: Dynamical symmetry in spinor Bose-Einstein condensates
Authors: Shun Uchino, Takaharu Otsuka, Masahito Ueda
Categories: cond-mat.other nucl-th
Comments: 17 pages, 4 figures
Journal-ref: Physical Review A 78, 023609 (2008)
DOI: 10.1103/PhysRevA.78.023609
\\ ( , 108kb)
replaced with revised version Tue, 12 Aug 2008 06:09:25 GMT (760kb,D)

Title: Two-channel Feshbach physics in a structured continuum
Authors: N. Nygaard, R. Piil, and K. Molmer
Categories: cond-mat.other quant-ph
Comments: 18 pages, 9 embedded figures
Journal-ref: Phys. Rev. A 78, 023617 (2008)
DOI: 10.1103/PhysRevA.78.023617
\\ ( , 760kb)
replaced with revised version Tue, 12 Aug 2008 10:35:10 GMT (157kb)

Title: Cold Fermi atomic gases in a pumped optical resonator
Authors: Jonas Larson, Giovanna Morigi, Maciej Lewenstein
Categories: quant-ph cond-mat.other
Comments: Two column, three figures. Replaced with final version
Journal-ref: Phys. Rev. A 78, 023815 (2008)
DOI: 10.1103/PhysRevA.023815
\\ ( , 157kb)
replaced with revised version Wed, 13 Aug 2008 15:49:36 GMT (12kb)

Title: Phonon background versus analogue Hawking radiation in Bose-Einstein
Authors: S. Wuester
Categories: cond-mat.other gr-qc
Comments: 4 pages, no figures, revised version
Journal-ref: Phys. Rev. A 78 (2008) 021601(R)
DOI: 10.1103/PhysRevA.78.021601
\\ ( , 12kb)
replaced with revised version Wed, 13 Aug 2008 15:56:38 GMT (1224kb,D)

Title: Determination of the Superfluid Gap in Atomic Fermi Gases by
   Quasiparticle Spectroscopy
Authors: Andre Schirotzek, Yong-il Shin, Christian H. Schunck and Wolfgang
Categories: cond-mat.other
Comments: 5 pages, 4 figures (appendix: 3 pages, 5 figures)
\\ ( , 1224kb)
replaced with revised version Wed, 13 Aug 2008 02:25:48 GMT (27kb)

Title: Quantum phase transition using quantum walks in an optical lattice
Authors: C. M. Chandrashekar and Raymond Laflamme
Categories: quant-ph cond-mat.other physics.atom-ph
Comments: 7 pages, 8 figures
Journal-ref: Phys. Rev. A 78, 022314 (2008)
DOI: 10.1103/PhysRevA.78.022314
\\ ( , 27kb)
replaced with revised version Thu, 14 Aug 2008 15:17:27 GMT (327kb,D)

Title: Macroscopic superposition states in rotating ring lattices
Authors: Andreas Nunnenkamp and Ana Maria Rey
Categories: cond-mat.other
Comments: 8 pages, 4 figures; PQE-2008 conference proceedings; minor
\\ ( , 327kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Fri Sep 26 2008 - 08:41:08 EST

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