Matt's arXiv selection: week ending 28 November 2008

From: Matthew Davis <>
Date: Tue, 06 Jan 2009 09:40:38 +1000

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

Hi everyone,

I have spend the last month away from home, and despite the best of intentions I
didn't manage to complete any arXiv selection emails. I hope to quickly catch
up in the coming days.

I would like to wish all subscribers a happy new year!

There are 31 new preprints and 4 replacements in this post.

Date: Fri, 21 Nov 2008 02:19:24 GMT (203kb)

Title: LDA+Gutzwiller Method for Correlated Electron Systems: Formalism and Its
Authors: XiaoYu Deng, Lei Wang, Xi Dai, Zhong Fang
Categories: cond-mat.str-el
Comments: 20 pages, 11 figures
   We introduce in detail our newly developed \textit{ab initio}
   LDA+Gutzwiller method, in which the Gutzwiller variational approach is
naturally incorporated with the density functional theory (DFT) through the
"Gutzwiller density functional theory (GDFT)" (which is a generalization of
original Kohn-Sham formalism). This method can be used for ground state
determination of electron systems ranging from weakly correlated metal to
strongly correlated insulators with long-range ordering. We will show that its
quality for ground state is as high as that by dynamic mean field theory
(DMFT), and yet it is computationally much cheaper. In additions, the method is
fully variational, the charge-density self-consistency can be naturally
achieved, and the quantities, such as total energy, linear response, can be
accurately obtained similar to LDA-type calculations. Applications on several
typical systems are presented, and the characteristic aspects of this new
method are clarified. The obtained results using LDA+Gutzwiller are in better
agreement with existing experiments, suggesting significant improvements over
\\ ( , 203kb)
Date: Fri, 21 Nov 2008 16:45:53 GMT (38kb)

Title: Three-body Recombination of Fermionic Atoms with Large Scattering
Authors: Eric Braaten, H.-W. Hammer, Daekyoung Kang, Lucas Platter
Categories: cond-mat.other
Comments: 4 pages, 4 figures
Report-no: HISKP-TH-08/19
   The 3-body recombination rate at threshold for fermions with three spin
states and large scattering lengths is calculated in the zero-range
approximation. The only parameters in this limit are the three scattering
lengths and the Efimov parameter, which can be complex valued. Semi-analytic
results are obtained for the cases of negative scattering lengths, two of which
are equal. The general result is applied to the three lowest hyperfine states
of Lithium-6 atoms in regions of the magnetic field in which the three
scattering lengths are all large and negative. Comparisons with recent
experiments provide indications of loss features associated with Efimov trimers
near the 3-atom threshold.
\\ ( , 38kb)
Date: Fri, 21 Nov 2008 18:15:41 GMT (55kb)

Title: Solid 4He and the Supersolid Phase: from Theoretical Speculation to the
   Discovery of a New State of Matter? A Review of the Past and Present Status
   of Research
Authors: D.E. Galli and L. Reatto
Categories: cond-mat.stat-mech
Comments: Published on J. Phys. Soc. Jpn., Vol.77, No.11, p.111010
   The possibility of a supersolid state of matter, i.e., a crystalline solid
exhibiting superfluid properties, first appeared in theoretical studies about
forty years ago. After a long period of little interest due to the lack of
experimental evidence, it has attracted strong experimental and theoretical
attention in the last few years since Kim and Chan (Penn State, USA) reported
evidence for nonclassical rotational inertia effects, a typical signature of
superfluidity, in samples of solid 4He. Since this "first observation", other
experimental groups have observed such effects in the response to the rotation
of samples of crystalline helium, and it has become clear that the response of
the solid is extremely sensitive to growth conditions, annealing processes, and
3He impurities. A peak in the specific heat in the same range of temperatures
has been reported as well as anomalies in the elastic behaviour of solid 4He
with a strong resemblance to the phenomena revealed by torsional oscillator
experiments. Very recently, the observation of unusual mass transport in hcp
solid 4He has also been reported, suggesting superflow. From the theoretical
point of view, powerful simulation methods have been used to study solid 4He,
but the interpretation of the data is still rather difficult; dealing with the
question of supersolidity means that one has to face not only the problem of
the coexistence of quantum coherence phenomena and crystalline order, exploring
the realm of spontaneous symmetry breaking and quantum field theory, but also
the problem of the role of disorder, i.e., how defects, such as vacancies,
impurities, dislocations, and grain boundaries, participate in the phase
transition mechanism.
\\ ( , 55kb)
Date: Fri, 21 Nov 2008 19:56:48 GMT (65kb)

Title: Superfluid-density of the ultra-cold Fermi gas in optical lattices
Authors: T. Paananen
Categories: cond-mat.other
Comments: 20 pages, 7 figures
   In this paper we study the superfluid density of the two component Fermi gas
in optical lattices with population imbalance. Three different type of phases,
the BCS-state (Bardeen, Cooper, and Schieffer), the FFLO-state (Fulde, Ferrel,
Larkin, and Ovchinnikov), and Sarma state, are considered. We show that the
FFLO superfluid density differs crucially from the BCS/Sarma superfluid
density. Although there are dynamical instabilities in the FFLO phase, when the
interaction is strong or densities are high, on the weak coupling limit the
FFLO phase is stable.
\\ ( , 65kb)
Date: Fri, 21 Nov 2008 10:48:55 GMT (189kb,D)

Title: Negative specific heat from the partition function of a free damped
Authors: Gert-Ludwig Ingold, Peter H\"anggi, and Peter Talkner
Categories: quant-ph cond-mat.stat-mech
Comments: 7 pages, 6 figures, physeauth.cls and elsart.cls v2.18 included
   The definition of the specific heat for a damped quantum system is a subtle
issue. A possible approach is based on an effective partition function defined
as the ratio of the partition functions of system plus bath and of the bath
alone. For the free damped particle it has been shown, however, that the
ensuing specific heat may become negative for appropriately chosen
environments. We argue that this quantity should be interpreted as the change
of the specific heat of the heat bath when the system degrees of freedom are
coupled to it. While this difference may become negative, the involved specific
heats themselves are always positive and therefore thermodynamic stability is
always guaranteed. For a damped harmonic oscillator, instead of negative
values, under appropriate conditions one can observe a dip in the difference of
specific heats as a function of temperature. Minimal models containing a single
oscillator heat bath are employed to elucidate the temperature dependence of
the difference of specific heats. Finally, we comment on the consequences for
the interpretation of the density of states based on the effective partition
\\ ( , 189kb)
Date: Sat, 22 Nov 2008 12:16:45 GMT (155kb)

Title: STIRAP transport of Bose-Einstein condensate in triple-well trap
Authors: V.O. Nesterenko, A.N. Novikov, F.F. de Souza Cruz, and E.L. Lapolli
Categories: cond-mat.other
Comments: 9 pages, 6 figures. To be published in Laser Physics (v. 19, n.4,
   The irreversible transport of multi-component Bose-Einstein condensate (BEC)
is investigated within the Stimulated Adiabatic Raman Passage (STIRAP) scheme.
A general formalism for a single BEC in M-well trap is derived and analogy
between multi-photon and tunneling processes is demonstrated. STIRAP transport
of BEC in a cyclic triple-well trap is explored for various values of detuning
and interaction between BEC atoms. It is shown that STIRAP provides a complete
population transfer at zero detuning and interaction and persists at their
modest values. The detuning is found not to be obligatory. The possibility of
non-adiabatic transport with intuitive order of couplings is demonstrated.
Evolution of the condensate phases and generation of dynamical and geometric
phases are inspected. It is shown that STIRAP allows to generate the
unconventional geometrical phase which is now of a keen interest in quantum
\\ ( , 155kb)
Date: Sun, 23 Nov 2008 17:38:12 GMT (1291kb)

Title: The quantum optical Josephson interferometer
Authors: Dario Gerace, Hakan E. Tureci, A. Imamoglu, Vittorio Giovannetti and
   Rosario Fazio
Categories: cond-mat.mes-hall
Comments: 9 pages, 7 figures
   The interplay between coherent tunnel coupling and on-site interactions in
dissipation-free bosonic systems has lead to many spectacular observations,
ranging from the demonstration of number-phase uncertainty relation to quantum
phase transitions. To explore the effect of dissipation and coherent drive on
tunnel coupled interacting bosonic systems, we propose a device that is the
quantum optical analog of a Josephson interferometer. It consists of two
coherently driven linear optical cavities connected via a central cavity with a
single-photon nonlinearity. The Josephson-like oscillations in the light
emitted from the central cavity as a function of the phase difference between
two pumping fields can be suppressed by increasing the strength of the
nonlinear coupling. Remarkably, we find that in the limit of ultra-strong
interactions in the center-cavity, the coupled system maps on to an effective
Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling
strength. In the limit of a single nonlinear cavity coupled to two linear
waveguides, the degree of photon antibunching from the nonlinear cavity
provides an excellent measure of the transition to the nonlinear regime where
Josephson oscillations are suppressed.
\\ ( , 1291kb)
Date: Mon, 24 Nov 2008 14:07:24 GMT (413kb)

Title: Finite Temperature Phase Diagram in Rotating Bosonic Optical Lattice
Authors: Beibing Huang, Shaolong Wan
Categories: cond-mat.str-el
Comments: 10 pages, 2 figures
   Finite temperature phase boundary between superfluid phase and normal state
is analytically derived by studying the stability of normal state in rotating
bosonic optical lattice. We also prove that the oscillation behavior of
critical hopping matrix directly follows the upper boundary of Hofstadter
butterfly as the function of effective magnetic field.
\\ ( , 413kb)
Date: Mon, 24 Nov 2008 02:52:08 GMT (6kb)

Title: Oscillation of Pauli Paramagnetism in Rotating Two-Component Fermionic
   Atom Gases
Authors: Beibing Huang, Shaolong Wan
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 5 pages,
   By rotating two-component fermionic atom gases in uniform magnetic field, a
similar physical situation with de Haas-van Alphen effect is constructed. We
calculate magnetic moment of the system and find that owing to an existence of
effective magnetic field coming from the rotation, the magnetic moment also
shows the oscillatory behavior about magnetic field, but it is completely
different from the famous oscillation of de Haas-van Alphen effect. This
distinction is due to that in the atomic gases the orbital motion of atom only
couples to rotation and does not contribute to magnetic moment in the light of
atomic charge neutrality.
\\ ( , 6kb)
Date: Mon, 24 Nov 2008 14:34:37 GMT (60kb)

Title: Polaron Properties of an Impurity in Bose-Einstein-Condensation
Authors: Beibing Huang, Shaolong Wan
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 13 pages, 3 figures
   In this paper we study an impurity in Bose-Einstein-Condensate system at
$T=0K$ and suppose the contact forms for boson-boson and boson-impurity
interactions. Using Bogoliubov theory and a further approximation corresponding
to only think over the forward scattering of impurity by bosons, we derive a
reduced Hamiltonian whose form is the same as the Fr\"{o}hlich Hamiltonian for
large polaron. By using Lee-Low-Pines (LLP) theory for large polaron, we obtain
the effective mass of impurity, the phonon number carried by impurity and the
energy related to the existence of impurity. In addition, we also discuss the
valid range for forward-scattering approximation.
\\ ( , 60kb)
Date: Mon, 24 Nov 2008 17:37:51 GMT (26kb)

Title: Microwave Photon Detector in Circuit QED
Authors: G. Romero, J. J. Garcia-Ripoll, E. Solano
Categories: cond-mat.mes-hall
   Quantum optical photodetection has occupied a central role in understanding
radiation-matter interactions. It has also contributed to the development of
atomic physics and quantum optics, including applications to metrology,
spectroscopy, and quantum information processing. The quantum microwave regime,
originally explored using cavities and atoms, is seeing a novel boost with the
generation of nonclassical propagating fields in circuit quantum
electrodynamics (QED). This promising field, involving potential developments
in quantum information with microwave photons, suffers from the absence of
photodetectors. Here, we design a metamaterial composed of discrete
superconducting elements that implements a high-efficiency microwave photon
detector. Our design consists of a microwave guide coupled to an array of
metastable quantum circuits, whose internal states are irreversibly changed due
to the absorption of photons. This proposal can be widely applied to different
physical systems and can be generalized to implement a microwave photon
\\ ( , 26kb)
Date: Mon, 24 Nov 2008 20:58:55 GMT (1108kb,D)

Title: A practical scheme for a light-induced gauge field in an atomic Bose gas
Authors: Kenneth J. G\"{u}nter, Marc Cheneau, Tarik Yefsah, Steffen Patrick
   Rath, and Jean Dalibard
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: 4 pages, 3 figures
   We propose a scheme to generate an Abelian gauge field in an atomic gas using
two crossed laser beams. If the internal atomic state follows adiabatically the
eigenstates of the atom-laser interaction, Berry's phase gives rise to a vector
potential that can nucleate vortices in a Bose gas. The present scheme operates
even for a large detuning with respect to the atomic resonance, making it
applicable to alkali atoms without significant heating due to spontaneous
emission. We test the validity of the adiabatic approximation by integrating
the set of coupled Gross-Pitaevskii equations associated with the various
internal atomic states, and we show that the steady state of the interacting
gas indeed exhibits a vortex lattice, as expected from the adiabatic gauge
\\ ( , 1108kb)
Date: Fri, 21 Nov 2008 21:03:19 GMT (996kb,D)

Title: Accurate Microwave Control and Real-Time Diagnostics of Neutral Atom
Authors: W. Rakreungdet (1), J. H. Lee (1), K. F. Lee (2), B. E. Mischuck (3),
   Enrique Montano (1) and P. S. Jessen (1) ((1) College of Optical Sciences,
   University of Arizona, (2) Department of Physics, Michigan Technological
   University, (3) Department of Physics and Astronomy, University of New
Categories: quant-ph
Comments: 9 pages, 7 figures
   We demonstrate accurate single-qubit control in an ensemble of atomic qubits
trapped in an optical lattice. The qubits are driven with microwave radiation,
and their dynamics tracked by optical probe polarimetry. Real-time diagnostics
is crucial to minimize systematic errors and optimize the performance of
single-qubit gates, leading to fidelities of 0.99 for single-qubit pi
rotations. We show that increased robustness to large, deliberately introduced
errors can be achieved through the use of composite rotations. However, during
normal operation the combination of very small intrinsic errors and additional
decoherence during the longer pulse sequences precludes any significant
performance gain in our current experiment.
\\ ( , 996kb)
Date: Mon, 24 Nov 2008 12:17:11 GMT (33kb)

Title: Many-body theory for systems with particle conversion: Extending the
   multiconfigurational time-dependent Hartree method
Authors: Ofir E. Alon, Alexej I. Streltsov, and Lorenz S. Cederbaum
Categories: quant-ph
Comments: 46 pages
   We derive a multiconfigurational time-dependent Hartree theory for systems
with particle conversion. In such systems particles of one kind can convert to
another kind and the total number of particles varies in time. The theory thus
extends the scope of the available and successful multiconfigurational
time-dependent Hartree methods -- which were solely formulated for and applied
to systems with a fixed number of particles -- to new physical systems and
problems. As a guiding example we treat explicitly a system where bosonic atoms
can combine to form bosonic molecules and vise versa. In the theory for
particle conversion, the time-dependent many-particle wavefunction is written
as a sum of configurations made of a different number of particles, and
assembled from sets of atomic and molecular orbitals. Both the expansion
coefficients and the orbitals forming the configurations are time-dependent
quantities that are fully determined according to the Dirac-Frenkel
time-dependent variational principle. Particular attention is paid to the
reduced density matrices of the many-particle wavefunction that appear in the
theory and enter the equations of motion. There are two kinds of reduced
density matrices: particle-conserving reduced density matrices which directly
only couple configurations with the same number of atoms and molecules, and
particle non-conserving reduced density matrices which couple configurations
with a different number of atoms and molecules. Closed-form and compact
equations of motion are derived for contact as well as general two-body
interactions, and their properties are analyzed and discussed.
\\ ( , 33kb)
Date: Sun, 23 Nov 2008 22:42:53 GMT (370kb)

Title: Lattice Interferometer for Ultra-Cold Atoms
Authors: Mikkel F. Andersen, Tycho Sleator
Categories: physics.atom-ph
   We demonstrate an atomic interferometer based on ultra-cold atoms released
from an optical lattice. This technique yields a large improvement in signal to
noise over a related interferometer previously demonstrated. The interferometer
involves diffraction of the atoms using a pulsed optical lattice. For short
pulses a simple analytical theory predicts the expected signal. We investigate
the interferometer for both short pulses and longer pulses where the analytical
theory break down. Longer pulses can improve the precision and signal size. For
specific pulse lengths we observe a coherent signal at times that differs
greatly from what is expected from the short pulse model. The interferometric
signal also reveals information about the dynamics of the atoms in the lattice.
We investigate the application of the interferometer for a measurement of
$h/m_A$ that together with other well known constants constitutes a measurement
of the fine structure constant.
\\ ( , 370kb)
Date: Tue, 25 Nov 2008 08:53:21 GMT (428kb)

Title: Analysis and calibration of absorptive images of Bose-Einstein
   condensate at non-zero temperatures
Authors: J. Szczepkowski, R. Gartman, M. Witkowski, L. Tracewski, M. Zawada, W.
Categories: cond-mat.other
Comments: 17 pages, 8 figures
   We describe the method allowing quantitative interpretation of absorptive
images of mixtures of BEC and thermal atoms which reduces possible systematic
errors associated with evaluation of the contribution of each fraction. By
using known temperature dependence of the BEC fraction, the analysis allows
precise calibration of the fitting results. The developed method is verified in
two different measurements and compares well with theoretical calculations and
with measurements performed by another group.
\\ ( , 428kb)
Date: Tue, 25 Nov 2008 18:10:13 GMT (207kb)

Title: Coupling internal atomic states in a two-component Bose-Einstein
   condensate via an optical lattice: Extended Mott-superfluid transitions
Authors: Jonas Larson and Jani-Petri Martikainen
Categories: cond-mat.other
Comments: 9 pages, 7 figures
   An ultracold gas of coupled two-component atoms in an optical lattice is
studied. A systematic derivation of a Bose-Hubbard model is presented, and we
explicitly demonstrate that the hopping coefficient amongst neighboring sites
may be tuned between positive and negative values. This originates from the
interplay between atomic kinetic, atomic internal and atom-atom interaction
energies. As a consequence, the superfluid phase is divided into ferromagnetic
and antiferromagnetic like states. Furthermore, also the Mott phase is
separated into two distinguishable states. By means of the strong coupling
expansion, we find the full phase diagram of the four different phases.
\\ ( , 207kb)
Date: Mon, 24 Nov 2008 21:01:32 GMT (1143kb,D)

Title: Dynamical Coupling between a Bose-Einstein Condensate and a Cavity
   Optical Lattice
Authors: Stephan Ritter, Ferdinand Brennecke, Christine Guerlin, Kristian
   Baumann, Tobias Donner, Tilman Esslinger
Categories: quant-ph
Comments: 5 pages, 4 figures
   A Bose-Einstein condensate is dispersively coupled to a single mode of an
ultra-high finesse optical cavity. The system is governed by strong
interactions between the atomic motion and the light field even at the level of
single quanta. While coherently pumping the cavity mode the condensate is
subject to the cavity optical lattice potential whose depth depends nonlinearly
on the atomic density distribution. We observe bistability already below the
single photon level and strong back-action dynamics which tunes the system
periodically out of resonance.
\\ ( , 1143kb)
Date: Mon, 24 Nov 2008 21:06:30 GMT (122kb)

Title: Prospects for application of ultracold Sr$_2$ molecules in precision
Authors: S. Kotochigova, T. Zelevinsky, and Jun Ye
Categories: quant-ph
Comments: 8 pages, 10 figures
   Precision measurements with ultracold molecules require development of robust
and sensitive techniques to produce and interrogate the molecules. With this
goal, we theoretically analyze factors that affect frequency measurements
between rovibrational levels of the Sr$_2$ molecule in the electronic ground
state. This measurement can be used to constrain the possible time variation of
the proton-electron mass ratio. Sr$_2$ is expected to be a strong candidate for
achieving high precision due to the spinless nature and ease of cooling and
perturbation-free trapping of Sr \cite{Zelevinsky2008}. The analysis includes
calculations of two-photon transition dipole moments between deeply and weakly
bound vibrational levels, lifetimes of intermediate excited states, and Stark
shifts of the vibrational levels by the optical lattice field, including
possibilities of Stark-cancellation trapping.
\\ ( , 122kb)
Date: Mon, 24 Nov 2008 23:19:11 GMT (30kb)

Title: Bloch-Zener oscillations of atoms inside an optical cavity
Authors: B. Prasanna Venkatesh, M. Trupke, E.A. Hinds, D.H.J. O'Dell
Categories: quant-ph
Comments: 4 pages, 2 figures
   Cold atoms in an optical lattice execute Bloch-Zener oscillations when they
are accelerated. We investigate the corresponding behavior of the atoms and the
light when the optical lattice is provided by the intra-cavity field of a
driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we
find that their back-action modulates the phase and intensity of the light
transmitted through the cavity. We solve the coupled atom-light equations
self-consistently and show that, remarkably, the Bloch period is unaffected by
this back-action. The transmitted light provides a way to observe the atomic
oscillation continuously, allowing very high precision measurements to be
derived from a single cloud of atoms.
\\ ( , 30kb)
Date: Mon, 24 Nov 2008 23:07:23 GMT (1190kb)

Title: Variation of the Fine-Structure Constant and Laser Cooling of Atomic
Authors: N. A. Leefer, A. Cing\"oz, D. Budker, S. J. Ferrell, V. V. Yashchuk,
   A. Lapierre, A.-T Nguyen, S. K. Lamoreaux, J. R. Torgerson
Categories: physics.atom-ph
Comments: 10 pages, 6 figures
   Radio-frequency electric-dipole transitions between nearly degenerate,
opposite parity levels of atomic dysprosium (Dy) were monitored over an
eight-month period to search for a variation in the fine-structure constant,
$\alpha$. The data provide a rate of fractional temporal variation of $\alpha$
of $(-2.7\pm2.6)\times 10^{-15}$ yr$^{-1}$ or a value of $(-8.7 \pm 6.6) \times
10^{-6}$ for $k_\alpha$, the variation coefficient for $\alpha$ in a changing
gravitational potential. All results indicate the absence of significant
variation at the present level of sensitivity. We also present initial results
on laser cooling of an atomic beam of dysprosium.
\\ ( , 1190kb)
Date: Tue, 25 Nov 2008 03:37:56 GMT (258kb)

Title: Lifetime measurements of the 5d states of rubidium
Authors: D. Sheng and A. Perez Galvan and L. A. Orozco
Categories: physics.atom-ph
Comments: 9 pages, 6 figures
   We present lifetime measurements of the $5D_{3/2}$ and $5D_{5/2}$ states of
rubidium using the time correlated single photon counting method. We perform
the experiment in a magneto-optical trap of $^{87}$Rb atoms using a two-step
excitation with the trap laser at 780 nm as the first step. We record the 761.9
nm fluorescence from the decay of the $5D_{3/2}$ state to the $5P_{1/2}$ state,
and measure the lifetime of the $5D_{3/2}$ state $\tau=246.3(1.6)$ ns. We
record the 420.2 nm fluorescence from the cascade decay of the $5D_{5/2}$ state
to the $5S_{1/2}$ state through the $6P_{3/2}$ state, and extract the lifetime
of the $5D_{5/2}$ state ${\tau}=238.5(2.3)$ ns.
\\ ( , 258kb)
Date: Tue, 25 Nov 2008 14:19:25 GMT (320kb,D)

Title: A possible Efimov trimer state in 3-component lithium 6
Authors: Pascal Naidon and Masahito Ueda
Categories: physics.atom-ph
Comments: 4 pages, 2 figures
   We consider the Efimov trimer theory as a possible framework to explain
recently observed losses by inelastic three-body collisions in a
three-hyperfine-component ultracold mixture of lithium 6. Within this
framework, these losses would arise chiefly from the existence of an Efimov
trimer bound state below the continuum of free triplets of atoms, and the loss
maxima (at certain values of an applied magnetic field) would correspond to
zero-energy resonances where the trimer dissociates into three free atoms. Our
results show that such a trimer state is indeed possible given the two-body
scattering lengths in the three-component lithium mixture, and gives rise to
two zero-energy resonances. The locations of these resonances appear to be
consistent with observed losses.
\\ ( , 320kb)
Date: Tue, 25 Nov 2008 16:39:50 GMT (898kb,D)

Title: Nonadiabatic transitions in electrostatically trapped ammonia molecules
Authors: Moritz Kirste, Boris Saratakov, Melanie Schnell, Gerard Meijer
Categories: physics.atom-ph physics.chem-ph
   Nonadiabatic transitions are known to be major loss channels for atoms in
magnetic traps, but have thus far not been experimentally reported upon for
trapped molecules. We have observed and quantified losses due to nonadiabatic
transitions for three isotopologues of ammonia in electrostatic traps, by
comparing the trapping times in traps with a zero and a non-zero electric field
at the center. Nonadiabatic transitions are seen to dominate the overall loss
rate even for samples at relatively high temperatures of 10-50 mK.
\\ ( , 898kb)
Date: Wed, 26 Nov 2008 12:31:07 GMT (111kb,D)

Title: Scattering Resonances in a Degenerate Fermi Gas
Authors: K. J. Challis, N. Nygaard, K. M{\o}lmer
Categories: cond-mat.other
Comments: 8 pages, 5 figures
   We consider elastic single-particle scattering from a one-dimensional
two-component trapped superfluid Fermi gas when the incoming projectile
particle is identical to one of the confined species. Our theoretical treatment
is based on the Hartree-Fock ground state of the trapped gas and a
configuration-interaction description of the excitations. We determine the
scattering phase shifts for the system and predict Fano-type scattering
resonances that are a direct consequence of inter-atomic pairing. We describe
the main characteristics of the scattering resonances and make a comparison
with the results of BCS mean-field theory.
\\ ( , 111kb)
Date: Wed, 26 Nov 2008 15:01:59 GMT (15kb)

Title: Coherence properties of the microcavity polariton condensate
Authors: D. M. Whittaker and P. R. Eastham
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: 5 pages, 1 figure
   A theoretical model is presented which explains the dominant decoherence
process in a microcavity polariton condensate. The mechanism which is invoked
is the effect of self-phase modulation, whereby interactions transform
polariton number fluctuations into random energy variations. The model shows
that the phase coherence decay, g1(t), has a Kubo form, which can be Gaussian
or exponential, depending on whether the number fluctuations are slow or fast.
This fluctuation rate also determines the decay time of the intensity
correlation function, g2(t), so it can be directly determined experimentally.
The model explains recent experimental measurements of a relatively fast
Gaussian decay for g1(t), but also predicts a regime, further above threshold,
where the decay is much slower.
\\ ( , 15kb)
Date: Tue, 25 Nov 2008 23:42:05 GMT (562kb)

Title: Investigation of dephasing rates in an interacting Rydberg gas
Authors: U. Raitzsch, R. Heidemann, H. Weimer, V. Bendkowsky, B. Butscher, P.
   Kollmann, R. L\"ow, H. P. B\"uchler, T. Pfau
Categories: quant-ph
Comments: 13 pages, 5 figures
   We experimentally and theoretically investigate the dephasing rates of the
coherent evolution of a resonantly driven pseudo spin emersed in a reservoir of
pseudo spins. The pseudo spin is realized by optically exciting 87 Rb atoms to
a Rydberg state. Hence, the upper spin states are coupled via the strong van
der Waals interaction. Two different experimental techniques to measure the
dephasing rates are shown: the 'rotary echo' technique known from nuclear
magnetic resonance physics and electromagnetically induced transparency. The
experiments are performed in a dense frozen Rydberg gas, either confined in a
magnetic trap or in an optical dipole trap. Additionally, a numerical
simulation is used to analyse the dephasing in the rotary echo experiments.
\\ ( , 562kb)
Date: Wed, 26 Nov 2008 13:38:21 GMT (17kb)

Title: Nonequilibrium thermal Casimir-Polder forces
Authors: Stefan Yoshi Buhmann and Stefan Scheel
Categories: quant-ph
Comments: 5 pages
   We study the nonequilibrium Casimir-Polder force on an atom prepared in an
incoherent superposition of internal energy-eigenstates, which is placed in a
magnetoelectric environment of nonuniform temperature. After solving the
coupled atom--field dynamics within the framework of macroscopic quantum
electrodynamics, we derive a general expression for the thermal Casimir-Polder
\\ ( , 17kb)
Date: Wed, 26 Nov 2008 15:12:57 GMT (462kb)

Title: Nonlinear dynamics of a cigar-shaped Bose-Einstein condensate coupled
   with a single cavity mode
Authors: J. M. Zhang, F. C. Cui, D. L. Zhou, and W. M. Liu
Categories: quant-ph
Comments: 8 pages, 5 figures
   We investigate the nonlinear dynamics of a combined system which is composed
of a cigar-shaped Bose-Einstein condensate and an optical cavity. The two sides
couple dispersively. This system is characterized by its nonlinearity: after
integrating out the freedom of the cavity mode, the potential felt by the
condensate depends on the condensate itself. We develop a discrete-mode
approximation for the condensate. Based on this approximation, we map out the
steady configurations of the system. It is found that due to the nonlinearity
of the system, the nonlinear levels of the system can fold up in some parameter
regimes. That will lead to the breakdown of adiabaticity. Analysis of the
dynamical stability of the steady states indicates that the same level
structure also results in optical bistability.
\\ ( , 462kb)
Date: Wed, 26 Nov 2008 12:04:56 GMT (192kb)

Title: A Feshbach resonance in d-wave collisions
Authors: Q. Beaufils, A. Crubellier, T. Zanon, B. Laburthe-Tolra, E. Marechal,
   L. Vernac, and O. Gorceix
Categories: physics.atom-ph
Comments: 8 pages, 5 figures
   We analyse a narrow Feshbach resonance with ultra-cold chromium atoms
colliding in d-wave. The resonance is made possible by dipole-dipole
interactions, which couple an incoming $l=2$ collision channel with a bound
molecular state with $l=0$. We find that three-body losses associated to this
resonance increase with temperature, and that the loss feature width as a
function of magnetic field also increases linearly with temperature. The
analysis of our experimental data shows that the Feshbach coupling is small
compared both to the temperature and to the density limited lifetime of the
resonant bound molecular state. One consequence is that the three body losse
rate is proportionnal to the square of the number of atoms, and that we can
directly relate the amplitude of the losses to the Feshbach coupling parameter.
We compare our measurement to a calculation of the coupling between the
collisionnal channel and the molecular bound state by dipole-dipole
interactions, and find a good agreement, with no adjustable parameter. An
analysis of the loss lineshape is also performed, which enables to precisely
measure the position of the resonance.
\\ ( , 192kb)
arXiv:0705.1845 (*cross-listing*)
Date: Sun, 13 May 2007 18:33:50 GMT (883kb)

Title: Introduction to protein folding for physicists
Authors: Pablo Echenique
Categories: cond-mat.soft physics.chem-ph q-bio.BM
Comments: 53 pages, 18 figures, the figures are at a low resolution due to
   arXiv restrictions, for high-res figures, go to
Journal-ref: Contemporary Physics 48 (2007) 81-108
DOI: 10.1080/00107510701520843
   The prediction of the three-dimensional native structure of proteins from the
knowledge of their amino acid sequence, known as the protein folding problem,
is one of the most important yet unsolved issues of modern science. Since the
conformational behaviour of flexible molecules is nothing more than a complex
physical problem, increasingly more physicists are moving into the study of
protein systems, bringing with them powerful mathematical and computational
tools, as well as the sharp intuition and deep images inherent to the physics
discipline. This work attempts to facilitate the first steps of such a
transition. In order to achieve this goal, we provide an exhaustive account of
the reasons underlying the protein folding problem enormous relevance and
summarize the present-day status of the methods aimed to solving it. We also
provide an introduction to the particular structure of these biological
heteropolymers, and we physically define the problem stating the assumptions
behind this (commonly implicit) definition. Finally, we review the 'special
flavor' of statistical mechanics that is typically used to study the
astronomically large phase spaces of macromolecules. Throughout the whole work,
much material that is found scattered in the literature has been put together
here to improve comprehension and to serve as a handy reference.
\\ ( , 883kb)

The replacements:

replaced with revised version Fri, 21 Nov 2008 18:02:43 GMT (21kb)

Title: DC Josephson Effect with Fermi gases in the Bose-Einstein regime
Authors: F. Ancilotto, L. Salasnich, and F. Toigo
Categories: cond-mat.other cond-mat.supr-con
Comments: 9 pages, 6 figures. In the new version added one figure and some
\\ ( , 21kb)
replaced with revised version Tue, 25 Nov 2008 16:15:11 GMT (249kb)

Title: Collisional decoherence in trapped atom interferometers that use
   non-degenerate sources
Authors: James A. Stickney, Matthew B. Squires, James Scoville, Paul Baker, and
   Steven Miller
Categories: physics.atom-ph
Comments: (23 pages, 5 figures)
\\ ( , 249kb)
replaced with revised version Tue, 25 Nov 2008 21:55:28 GMT (363kb)

Title: Superfluidity of fermions with repulsive on-site interaction in an
   anisotropic optical lattice near a Feshbach resonance
Authors: B. Wang and L.-M. Duan
Categories: cond-mat.other cond-mat.str-el
Comments: updated with published version;
Journal-ref: New Journal of Physics 10, 073007 (2008)
\\ ( , 363kb)
replaced with revised version Wed, 26 Nov 2008 16:12:48 GMT (108kb)

Title: Single-photon cooling to the limit of trap dynamics: Maxwell's Demon
   near maximum efficiency
Authors: S. Travis Bannerman, Gabriel N. Price, Kirsten Viering, and Mark G.
Categories: physics.atom-ph
\\ ( , 108kb)

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
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 Tue Jan 06 2009 - 10:40:06 EST

This archive was generated by hypermail 2.2.0 : Wed Feb 25 2009 - 08:32:44 EST