Matt's arXiv selection: week ending 8 February 2008

From: Matthew Davis <>
Date: Mon, 11 Feb 2008 08:32:16 +1000

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

Hi everyone,

This email list gained its 400th subscriber this week. I wonder what proportion
of researchers in the field that is?

We have 19 new preprints and 7 replacements this week:

Date: Fri, 1 Feb 2008 09:44:30 GMT (917kb)

Title: Dynamics of matter-wave solitons in a ratchet potential
Authors: Dario Poletti, Tristram J. Alexander, Elena A. Ostrovskaya, Baowen Li,
   Yuri S. Kivshar
Categories: cond-mat.other
Comments: 4 pages, 5 figures
   We study the dynamics of bright solitons formed in a Bose-Einstein condensate
with attractive atomic interactions perturbed by a weak bichromatic optical
lattice potential. The lattice depth is a biperiodic function of time with a
zero mean, which realises a flashing ratchet for matter-wave solitons. The
average velocity of a soliton and the directed soliton current induced by the
ratchet depend on the number of atoms in the soliton. We employ this feature to
study collisions between ratchet-driven solitons and find that soliton
transport can be induced through their interactions. In the regime when
matter-wave solitons are narrow compared to the lattice period the ratchet
dynamics is well described by the effective Hamiltonian theory.
\\ ( , 917kb)
Date: Fri, 1 Feb 2008 15:09:05 GMT (25kb)

Title: Phases in optical lattices vs. Coulomb frustrated HTc cuprates
Authors: Henning Heiselberg
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 8 pages, 3 figures
   Fermionic atoms in 2D optical lattices and electrons in HTc cuprates may both
be described by the Hubbard model. However, if Coulomb frustration is
responsible for the striped phases in 2D cuprates the phase diagrams will
differ markedly. Two representative scenarios are described by a simple stripe
model without phase separation and a mean field model with phase separation in
the absence of Coulomb frustration. When Coulomb frustrated both models display
antiferromagnetism (AF) and stripe phases with d-wave superfluidity, whereas
neutral atoms in optical lattices will only do so in the stripe model. Radii
and densities of the various phases in harmonically confined optical lattices
are calculated for the two models and have very different Mott plateaus and
density discontinuities. We discuss observation of antiferromagnetic, stripe
and superfluid phases in density and momentum distributions and correlations
from time-of-flight experiments.
\\ ( , 25kb)
Date: Wed, 30 Jan 2008 21:37:41 GMT (126kb,D)

Title: Self-organization of a Bose-Einstein condensate in an optical cavity
Authors: D. Nagy, G. Szirmai, P. Domokos
Categories: quant-ph cond-mat.other
Comments: 11 pages
   The spatial self-organization of a Bose-Einstein condensate (BEC) in a
high-finesse linear optical cavity is discussed. The condensate atoms are
laser-driven from the side and scatter photons into the cavity. Above a
critical pump intensity the homogeneous condensate evolves into a stable
pattern bound by the cavity field. The transition point is determined
analytically from a mean-field theory. We calculate the lowest lying Bogoliubov
excitations of the coupled BEC-cavity system and the quantum depletion due to
the atom-field coupling.
\\ ( , 126kb)

Date: Mon, 4 Feb 2008 07:51:01 GMT (970kb)

Title: Determination of the Fermion Pair Size in a Resonantly Interacting
Authors: Christian H. Schunck, Yong-il Shin, Andre Schirotzek, and Wolfgang
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 8 pages, 6 figures
   Fermionic superfluidity requires the formation of pairs. The actual size of
these fermion pairs varies by orders of magnitude from the femtometer scale in
neutron stars and nuclei to the micrometer range in conventional
superconductors. Many properties of the superfluid depend on the pair size
relative to the interparticle spacing. This is expressed in BCS-BEC crossover
theories, describing the crossover from a Bardeen-Cooper-Schrieffer (BCS) type
superfluid of loosely bound and large Cooper pairs to Bose-Einstein
condensation (BEC) of tightly bound molecules. Such a crossover superfluid has
been realized in ultracold atomic gases where high temperature superfluidity
has been observed. We probe the microscopic properties of the fermion pairs
with radio-frequency (rf) spectroscopy. Previous work was difficult to
interpret due to strong and not well understood final state interactions. Here
we realize a new superfluid spin mixture where such interactions have
negligible influence and present fermion-pair dissociation spectra that reveal
the underlying pairing correlations. This allows us to determine the fermion
pair size in the resonantly interacting gas to be 1.4(2)/kF, smaller than the
interparticle spacing and the smallest pairs observed in fermionic superfluids
(kF is the Fermi wave number). This finding highlights the importance of small
fermion pairs for superfluidity at high critical temperature. We have also
identified transitions from fermion pairs into bound molecular states and into
many-body bound states in the case of strong final state interactions.
\\ ( , 970kb)

Date: Mon, 4 Feb 2008 09:42:28 GMT (340kb)

Title: Three-dimensional character of atom-chip-based rf-dressed potentials
Authors: J. J. P. van Es, S. Whitlock, T. Fernholz, A. H. van Amerongen, N. J.
   van Druten
Categories: cond-mat.other
Comments: 9 pages, 7 figures
   We experimentally investigate the properties of radio-frequency-dressed
potentials for Bose-Einstein condensates on atom chips. The three-dimensional
potential forms a connected pair of parallel waveguides. We show that
rf-dressed potentials are robust against the effect of small magnetic-field
variations on the trap potential. Long-lived dipole oscillations of condensates
induced in the rf-dressed potentials can be tuned to a remarkably low damping
rate. We study a beam-splitter for Bose-Einstein condensates and show that a
propagating condensate can be dynamically split in two vertically separated
parts and guided along two paths. The effect of gravity on the potential can be
tuned and compensated for using a rf-field gradient.
\\ ( , 340kb)

Date: Mon, 4 Feb 2008 05:11:34 GMT (173kb)

Title: Magneto-Optical Stern-Gerlach Effect in Atomic Ensemble
Authors: Yu Guo, Lan Zhou, Le-Man Kuang, C.P. Sun
Categories: quant-ph
Comments: 4 pages, 3 figures
   We study the birefringence of the quantized polarized light in a
magneto-optically manipulated atomic ensemble as a generalized Stern-Gerlach
Effect of light. To explain this engineered birefringence microscopically, we
derive an effective Shr\"odinger equation for the spatial motion of two
orthogonally polarized components, which behave as a spin with an effective
magnetic moment leading to a Stern-Gerlach split in an nonuniform magnetic
field. We show that electromagnetic induced transparency (EIT) mechanism can
enhance the magneto-optical Stern-Gerlach effect of light in the presence of a
control field with a transverse spatial profile and a inhomogeneous magnetic
\\ ( , 173kb)

Date: Fri, 1 Feb 2008 23:31:55 GMT (30kb)

Title: Optical Lattice Induced Light Shifts in an Yb Atomic Clock
Authors: Z. W. Barber, J. E. Stalnaker, N. D. Lemke, N. Poli, C. W. Oates, T.
   M. Fortier, S. A. Diddams, L. Hollberg, C. W. Hoyt
Categories: physics.atom-ph
Comments: Accepted to PRL
   We present an experimental study of the lattice induced light shifts on the
1S_0-3P_0 optical clock transition (v_clock~518 THz) in neutral ytterbium. The
``magic'' frequency, v_magic, for the 174Yb isotope was determined to be 394
799 475(35)MHz, which leads to a first order light shift uncertainty of 0.38 Hz
on the 518 THz clock transition. Also investigated were the hyperpolarizability
shifts due to the nearby 6s6p 3P_0 - 6s8p 3P_0, 6s8p 3P_2, and 6s5f 3F_2
two-photon resonances at 759.708 nm, 754.23 nm, and 764.95 nm respectively. By
tuning the lattice frequency over the two-photon resonances and measuring the
corresponding clock transition shifts, the hyperpolarizability shift was
estimated to be 170(33) mHz for a linear polarized, 50 uK deep, lattice at the
magic wavelength. In addition, we have confirmed that a circularly polarized
lattice eliminates the J=0 - J=0 two-photon resonance. These results indicate
that the differential polarizability and hyperpolarizability frequency shift
uncertainties in a Yb lattice clock could be held to well below 10-17.
\\ ( , 30kb)

Date: Mon, 4 Feb 2008 17:30:48 GMT (237kb)

Title: Inelastic Collisions in Optically Trapped Ultracold Metastable Ytterbium
Authors: A. Yamaguchi, S. Uetake, D. Hashimoto, J. M. Doyle, Y. Takahashi
Categories: physics.atom-ph
Comments: 4 pages, 4 figures
   We report measurement of inelastic loss in dense and cold metastable
ytterbium (Yb[$^3P_2$]). Use of an optical far-off-resonance trap enables us to
trap atoms in all magnetic sublevels, removing multichannel collisional trap
loss from the system. Trapped samples of Yb[$^3P_2$] are produced at a density
of 2$\times10^{13}$ cm$^{-3}$ and temperature of 2 $\mu$K. We observe rapid
two-body trap loss of Yb[$^3P_2$] and measure the inelastic collision rate
constant 1.0(3)$\times10^{-11}$ cm$^3$s$^{-1}$. The existence of the
fine-structure changing collisions between atoms in the $^3P_2$ state is
strongly suggested.
\\ ( , 237kb)

Date: Tue, 5 Feb 2008 18:01:42 GMT (230kb)

Title: Single-Photon Atomic Cooling
Authors: Gabriel N. Price, S. Travis Bannerman, Kirsten Viering, Edvardas
   Narevicius and Mark G. Raizen
Categories: physics.atom-ph
Comments: 4 pages and 3 figures
   We report the cooling of an atomic ensemble with light, where each atom
scatters only a single photon on average. This is a general method that does
not require a cycling transition and can be applied to atoms or molecules which
are magnetically trapped. We discuss the application of this new approach to
the cooling of hydrogenic atoms for the purpose of precision spectroscopy and
fundamental tests.
\\ ( , 230kb)
Date: Tue, 5 Feb 2008 21:33:02 GMT (391kb)

Title: Characteristics of Bose-Einstein condensation in an optical lattice
Authors: G.-D. Lin, Wei Zhang, and L.-M. Duan
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 12 pages, 11 figures
   We discuss several possible experimental signatures of the Bose-Einstein
condensation (BEC) transition for an ultracold Bose gas in an inhomogeneous
optical lattice. Based on the commonly used time-of-flight imaging technique,
we show that the momentum-space density profile in the first Brillouin zone,
supplemented by the visibility of interference patterns, provides valuable
information about the system. In particular, by crossing the BEC transition
temperature, the appearance of a clear bimodal structure sets a qualitative and
universal signature of this phase transition. Furthermore, the momentum
distribution can also be applied to extract the condensate fraction, which may
serve as a promising thermometer in such a system.
\\ ( , 391kb)
Date: Wed, 6 Feb 2008 01:43:32 GMT (150kb)

Title: Quasi-particle Tunneling in a Bose-Einstein Condensate
Authors: S. Tsuchiya, Y. Ohashi
Categories: cond-mat.other cond-mat.supr-con
Comments: 4 pages, 3 figures
   We investigate tunneling properties of Bogoliubov phonons in a Bose-Einstein
condensate. Including spatial variation of the condensate near a tunneling
barrier, we calculate the transmission probability of Bogoliubov phonon as well
as quasi-particle current by numerically solving the Bogoliubov equations. We
show that the quasi-particle current $J_{\rm q}$ is enhanced near the potential
barrier due to the supply of the excess current from the condensate. This
effect leads to the increase of quasi-particle transmission probability in the
low energy region. We also show that the quasi-particle current twists the
phase of the condensate wavefunction near the barrier, leading to a finite
Josephson supercurrent $J_{\rm s}$ across the barrier. This induced
supercurrent flows in the opposite direction to the quasi-particle current so
as to cancel out the enhancement of $J_{\rm q}$. The resulting total current
$J=J_{\rm q}+J_{\rm s}$ is conserved over the entire system.
\\ ( , 150kb)
Date: Wed, 6 Feb 2008 11:48:52 GMT (22kb)

Title: Variational wave functions for homogenous Bose systems
Authors: Andras Suto and Peter Szepfalusy
Categories: cond-mat.stat-mech
Journal-ref: Phys. Rev. A 77, 023606 (2008)
DOI: 10.1103/PhysRevA.77.023606
   We study variational wave functions of the product form, factorizing
according to the wave vectors k, for the ground state of a system of bosons
interacting via positive pair interactions with a positive Fourier transform.
Our trial functions are members of different orthonormal bases in Fock space.
Each basis contains a quasiparticle vacuum state and states with an arbitrary
finite number of quasiparticles. One of the bases is that of Valatin and Butler
(VB), introduced fifty years ago and parametrized by an infinite set of
variables determining Bogoliubov's canonical transformation for each k. In
another case, inspired by Nozi\`eres and Saint James the canonical
transformation for k=0 is replaced by a shift in the creation/annihilation
operators. For the VB basis we prove that the lowest energy is obtained in a
state with ~sqrt{volume} quasiparticles in the zero mode. The number of k=0
physical particles is of the order of the volume and its fluctuation is
anomalously large, resulting in an excess energy. The same fluctuation is
normal in the second type of optimized bases, the minimum energy is smaller and
is attained in a vacuum state. Associated quasiparticle theories and questions
about the gap in their spectrum are also discussed.
\\ ( , 22kb)
Date: Wed, 6 Feb 2008 15:29:16 GMT (544kb)

Title: Effect of magnetic fields on the spin evolution of non-polarized 87Rb
   Bose-Einstein condensates
Authors: Zhifeng Chen, C.G. Bao, Zhibing Li
Categories: cond-mat.other
Comments: 9 pages, 7 figures
   The spin mixing dynamics of spin-1 Bose-Einstein condensates with zero
magnetization and under an external magnetic field is investigated in a
systematic way. Beyond the mean field theory, the time-dependent solutions
under the single mode approximation are obtained via a procedure of
diagonalization of the Hamiltonian. Thereby the time-dependent populations of
atoms in spin component 0 starting from various initial states are obtained and
analyzed. The features of evolution are compared in detail with those with the
field removed so as to emphasize the effect of the field. Since the solutions
are exact for our Hamiltonian, we can study the long-term behavior of the
evolution. In particular, some special cases are found in which the evolution
is highly sensitive to the field, very strong oscillation in population can be
thereby induced. A new modes of oscillation of the population characterized by
having two frequencies, one is high and one is low, is found when the field is
sufficiently strong.
\\ ( , 544kb)
Date: Wed, 6 Feb 2008 15:16:17 GMT (50kb)

Title: The inherent fluctuations of pulsed atom laser produced in the F=2
Authors: Lin Xia, Fan Yang, Xiaoji Zhou and Xuzong Chen
Categories: physics.atom-ph
Comments: 4 pages, 5 figures
   The obvious fluctuations of pulsed atom laser beams are experimentally
observed under the condition that the back-coupling noise mechanics can be
neglected. The one-dimensional Gross-Pitaevskii model for atom lasers is used,
and the simulation fits the experiments. By analyzing the model, the noise is
induced due to the existence of the middle state between the initial state and
the output state. The fluctuations do not decrease by decreasing the coupling
strength, which is different from continuously outcoupled atom laser. It also
shows that the interference of outcoupled matter wave is a new noise mechanics
leading to severe fluctuations.
\\ ( , 50kb)
Date: Wed, 6 Feb 2008 16:32:40 GMT (782kb)

Title: Sub-Doppler laser cooling and magnetic trapping of erbium
Authors: Andrew J. Berglund, Siu Au Lee, Jabez J. McClelland
Categories: physics.atom-ph
Journal-ref: Phys. Rev. A 76, 053418 (2007)
DOI: 10.1103/PhysRevA.76.053418
   We investigate cooling mechanisms in magneto-optically and magnetically
trapped erbium. We find efficient sub-Doppler cooling in our trap, which can
persist even in large magnetic fields due to the near degeneracy of two Lande g
factors. Furthermore, a continuously loaded magnetic trap is demonstrated where
we observe temperatures below 25 microkelvin. These favorable cooling and
trapping properties suggest a number of scientific possibilities for rare-earth
atomic physics, including narrow linewidth laser cooling and spectroscopy,
unique collision studies, and degenerate bosonic and fermionic gases with
long-range magnetic dipole coupling.
\\ ( , 782kb)
Date: Wed, 6 Feb 2008 18:58:26 GMT (620kb)

Title: Narrow-line magneto-optical cooling and trapping of strongly magnetic
Authors: Andrew J. Berglund, James L. Hanssen, Jabez J. McClelland
Categories: physics.atom-ph
Comments: To appear in Phys. Rev. Lett. 4 pages, 5 figures
   Laser cooling on weak transitions is a useful technique for reaching
ultracold temperatures in atoms with multiple valence electrons. However, for
strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT)
is destabilized by competition between optical and magnetic forces. We overcome
this difficulty in Er by developing an unusual narrow-line MOT that balances
optical and magnetic forces using laser light tuned to the blue side of a
narrow (8 kHz) transition. The trap population is spin-polarized with
temperatures reaching below 2 microkelvin. Our results constitute an
alternative method for laser cooling on weak transitions, applicable to
rare-earth-metal and metastable alkaline earth elements.
\\ ( , 620kb)

Date: Thu, 7 Feb 2008 20:48:11 GMT (1712kb)

Title: Angle resolved power spectrum, squeezing spectrum and photon statistics
   from exciton condensate in Electron-Hole Bilayer Systems
Authors: T. Shi, Jinwu Ye and C. P. Sun
Categories: cond-mat.mtrl-sci cond-mat.mes-hall
Comments: REVTEX4, 2 columns, 14 pages, 16 colour figures
   We study quantum nature of photons emitted from the excitonic superfluid
phase in semiconductor electron-hole bilayer systems. We determine angle
resolved power spectrum, squeezing spectrum, one and two point correlation
functions along all the directions. We show that due to the non-vanishing order
parameter in the ESF phase, the emitted photons along the direction
perpendicular to the layer are in a coherent state. We also show that the
anomalous Green function of the exciton lead to a squeezed state of the emitted
photon along tilted directions. From the two point correlation function, we
find there are photon bunching, the photo-count statistics is super-Poissonian.
We comment on present experimental data and also suggest that all the
predictions can be measured by future angle resolved power spectrum, phase
sensitive homodyne measurements, and HanburyBrown-Twiss type of experiments. We
demonstrate explicitly that the photoluminescence from the exciton in EHBL
systems is a very natural, feasible and unambiguous internal probe of the
nature of quantum phases of excitons in EHBL such as the ground state and the
Bogoliubov excitations above the ground state even at zero temperature.
\\ ( , 1712kb)

Date: Thu, 7 Feb 2008 14:30:10 GMT (451kb)

Title: Progress in atom chips and the integration of optical microcavities
Authors: E. A. Hinds, M. Trupke, B. Darqui\'e, J. Goldwin, G. Dutier
Categories: quant-ph
Comments: 12 pages, 6 figures, proceedings of the ICOLS07 conference
   We review recent progress at the Centre for Cold Matter in developing atom
chips. An important advantage of miniaturizing atom traps on a chip is the
possibility of obtaining very tight trapping structures with the capability of
manipulating atoms on the micron length scale. We recall some of the pros and
cons of bringing atoms close to the chip surface, as is required in order to
make small static structures, and we discuss the relative merits of metallic,
dielectric and superconducting chip surfaces. We point out that the addition of
integrated optical devices on the chip can enhance its capability through
single atom detection and controlled photon production. Finally, we review the
status of integrated microcavities that have recently been demonstrated at our
Centre and discuss their prospects for future development.
\\ ( , 451kb)

... and this one is just for fun : I must admit, I've often considered this
problem as I silently fume over fellow passengers ignoring boarding instructions!

Date: Wed, 6 Feb 2008 04:20:41 GMT (104kb)

Title: Optimal boarding method for airline passengers
Authors: Jason H. Steffen
Categories: physics.soc-ph physics.pop-ph
Comments: 15 pages, 7 figures. Submitted to the Journal of Air Transportation
   Management. This study was motivated by an experience that occurred while
   traveling to a conference
   Using a Markov Chain Monte Carlo optimization algorithm and a computer
simulation, I find the passenger ordering which minimizes the time required to
board the passengers onto an airplane. The model that I employ assumes that the
time that a passenger requires to load his or her luggage is the dominant
contribution to the time needed to completely fill the aircraft. The optimal
boarding strategy may reduce the time required to board and airplane by over a
factor of four and possibly more depending upon the dimensions of the aircraft.
I explore some features of the optimal boarding method and discuss practical
modifications to the optimal. Finally, I mention some of the benefits that
could come from implementing and improved passenger boarding scheme.
\\ ( , 104kb)

The replacements:

replaced with revised version Fri, 1 Feb 2008 13:05:49 GMT (827kb,D)

Title: Exploring an ultracold Fermi-Fermi mixture: Interspecies Feshbach
   resonances and scattering properties of 6Li and 40K
Authors: E. Wille, F.M. Spiegelhalder, G. Kerner, D. Naik, A. Trenkwalder, G.
   Hendl, F. Schreck, R. Grimm, T.G. Tiecke, J.T.M. Walraven, S.J.J.M.F.
   Kokkelmans, E. Tiesinga, P.S. Julienne
Categories: cond-mat.other
Comments: 4 pages, 4 figures, 1 table
\\ ( , 827kb)
replaced with revised version Fri, 1 Feb 2008 05:35:34 GMT (83kb)

Title: Many-body quantum coherence and interaction blockade in Josephson-linked
   Bose-Einstein condensates
Authors: Chaohong Lee, Libin Fu, Yuri S. Kivshar
Categories: quant-ph
Comments: 6 pages, 5 figures, accepted for publication in EPL (Europhysics
\\ ( , 83kb)
replaced with revised version Sat, 2 Feb 2008 03:27:32 GMT (842kb)

Title: Quantum Entangled Dark Solitons Formed by Ultracold Atoms in Optical
Authors: R. V. Mishmash, L. D. Carr
Categories: cond-mat.mes-hall nlin.PS quant-ph
Comments: 4 pages, 4 figures
\\ ( , 842kb)
arXiv:0802.0446 (*cross-listing*)
Date: Mon, 4 Feb 2008 15:44:04 GMT (18kb)

Title: Spectral properties of the BCS gap equation of superfluidity
Authors: Christian Hainzl, Robert Seiringer
Categories: math-ph cond-mat.supr-con math.MP
Comments: Plenary talk given by C. Hainzl at QMath10, Moeciu, Romania,
   September 10-15, 2007
   We present a review of recent work on the mathematical aspects of the BCS gap
equation, covering our results of [arXiv:0801.4159] as well our recent joint
work with Hamza and Solovej [arXiv:math-ph/0703086] and with Frank and Naboko
[arXiv:0704.3564], respectively. In addition, we mention some related new
\\ ( , 18kb)
replaced with revised version Tue, 5 Feb 2008 07:45:13 GMT (419kb,D)

Title: Feshbach Molecules in a One-dimensional Optical Lattice
Authors: N. Nygaard, R. Piil and K. Molmer
Categories: cond-mat.other quant-ph
Comments: 4 pages, 3 figures
Journal-ref: Phys. Rev. A 77, 021601(R) (2008)
DOI: 10.1103/PhysRevA.77.021601
\\ ( , 419kb)
replaced with revised version Tue, 5 Feb 2008 09:33:30 GMT (306kb)

Title: Quantum Noise in the Coherent Matter-Wave Displacement Reaction
Authors: H. Jing, J. Cheng, and P. Meystre
Categories: quant-ph
Comments: 4 pages, 3 figures, submitted
\\ ( , 306kb)
replaced with revised version Thu, 7 Feb 2008 05:39:00 GMT (601kb)

Title: Density-Matrix Renormalization Group Study of Trapped Imbalanced Fermi
Authors: Masaki Tezuka and Masahito Ueda
Categories: cond-mat.str-el
Comments: 4 pages, 3 figures; added references; accepted for publication in
   Phys. Rev. Lett
\\ ( , 601kb)

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 Mon Feb 11 2008 - 11:03:08 EST

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