[Matts-arxiv] Matt's arXiv selection: week ending 18 June 2010

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Thu, 15 Jul 2010 14:06:53 +1000

Dear subscribers,

This week's selection was compiled by Geoff Lee, and contains 38 new
abstracts and 9 replacements.

arXiv:0912.1305 (*cross-listing*)
Date: Mon, 7 Dec 2009 18:53:47 GMT (242kb)
Date (revised v2): Fri, 11 Jun 2010 08:23:19 GMT (619kb,D)

Title: Vortex entanglement in Bose-Einstein condensates coupled to
   Laguerre-Gauss beams
Authors: N. Lo Gullo, S. McEndoo, Th. Busch, M. Paternostro
Categories: cond-mat.quant-gas quant-ph
Comments: 10 pages, 7 figures, RevTex4
Journal-ref: Phys. Rev. A 81, 053625 (2010)
   We study the establishment of vortex entanglement in remote and weakly
interacting Bose Einstein condensates. We consider a two-mode photonic resource
entangled in its orbital angular momentum (OAM) degree of freedom and, by
exploiting the process of light-to-BEC OAM transfer, demonstrate that such
entanglement can be efficiently passed to the matter-like systems. Our proposal
thus represents a building block for novel low-dissipation and long-memory
communication channels based on OAM. We discuss issues of practical
realizability, stressing the feasibility of our scheme and present an operative
technique for the indirect inference of the set vortex entanglement.
\\ ( http://arxiv.org/abs/0912.1305 , 619kb)
arXiv:1006.2160 (*cross-listing*)
Date: Thu, 10 Jun 2010 22:00:44 GMT (188kb,D)

Title: Many-Body Rate Limit on Photoassociation of a Bose-Einstein Condensate
Authors: Matt Mackie and Pierre Phou
Categories: cond-mat.quant-gas physics.atom-ph quant-ph
Comments: 4 pages, 3 figures, 58 references, submitted to PRA as Brief Report
   We briefly report on zero-temperature photoassociation of a Bose-Einstein
condensate, focusing on the many-body rate limit for atom-molecule conversion.
An upgraded model that explicitly includes spontaneous radiative decay leads to
an unanticipated shift in the position of the photoassociation resonance, which
affects whether the rate (constant) maximizes or saturates, as well as the
limiting value itself. A simple analytical model agrees with numerical
experiments, but only for high density. Finally, an explicit comparison with
the two-body unitary limit, set by the size of the condensate, finds that the
many-body rate limit is generally more strict.
\\ ( http://arxiv.org/abs/1006.2160 , 188kb)
Date: Thu, 10 Jun 2010 22:15:57 GMT (346kb)

Title: Exact results on the two-particle Green's function of a Bose-Einstein
Authors: Takafumi Kita
Categories: cond-mat.quant-gas cond-mat.stat-mech cond-mat.supr-con nucl-th
Comments: 5 pages, 2 figures, to appear in Phys. Rev. B
   Starting from the Dyson-Beliaev and generalized Gross-Pitaevskii equations
with an extra nonlocal potential, we derive an exact expression of the
two-particle Green's function K for an interacting Bose-Einstein condensate in
terms of unambiguously defined self-energies and vertices. The formula can be a
convenient basis for approximate calculations of K. It also tells us that poles
of K are not shared with (i.e. shifted from) those of the single-particle
Green's function, contrary to the conclusion of previous studies.
\\ ( http://arxiv.org/abs/1006.2161 , 346kb)
Date: Fri, 11 Jun 2010 09:44:32 GMT (127kb,D)

Title: Radio Frequency Association of Efimov Trimers
Authors: Thomas Lompe, Timo B. Ottenstein, Friedhelm Serwane, Andre N. Wenz,
   Gerhard Z\"urn and Selim Jochim
Categories: cond-mat.quant-gas
Comments: 14 pages, 6 figures
   The quantum-mechanical three-body problem is one of the fundamental
challenges of few-body physics. It becomes particularly interesting if the
two-body interactions between the particles become resonant. In 1970 V. Efimov
predicted that such systems can exhibit an infinite series of universal
three-body bound states whose properties are determined by the strength of the
two-body interactions. Here we report on the direct observation of such an
Efimov state with radio frequency (RF) association spectroscopy. We have
measured its binding energy as a function of interaction strength and found
good agreement with theoretical predictions. With this work both precision
studies and coherent manipulation of Efimov trimers have come into experimental
\\ ( http://arxiv.org/abs/1006.2241 , 127kb)
Date: Fri, 11 Jun 2010 11:21:43 GMT (2528kb)

Title: Magnetic Richtmyer-Meshkov instability in a two-component Bose-Einstein
Authors: A. Bezett, V. Bychkov, E. Lundh, D. Kobyakov, M. Marklund
Categories: cond-mat.quant-gas
Comments: 8 pages, 9 figures
   The magnetically induced Richtmyer-Meshkov instability in a two-component
Bose-Einstein condensate is investigated. We construct and study analytical
models describing the development of the instability at both the linear and
nonlinear stages. The models indicate new features of the instability: the
influence of quantum capillary waves and the separation of droplets, which are
qualitatively different from the classical case. We perform numerical
simulations of the instability in a trapped Bose-Einstein condensate using the
Gross-Pitaevskii equation and compare the simulation results to the model
\\ ( http://arxiv.org/abs/1006.2261 , 2528kb)
Date: Fri, 11 Jun 2010 11:42:44 GMT (40kb)

Title: Nielsen-Olesen string field theory and the Abelian-Higgs duality in 3+1
   and higher dimensions
Authors: A.J. Beekman, D. Sadri and J. Zaanen
Categories: cond-mat.str-el hep-th
Comments: RevTeX, 12 pages, 4 figures
   The Abelian-Higgs (or vortex, XY) duality in 2+1 dimensions demonstrates that
the quantum disordered superfluid is equivalent to an ordered superconductor
and the other way around. Such a duality structure should be ubiquitous but in
3+1 (and higher) dimensions a precise formulation of the duality is lacking.
The problem is that the topological defects become extended objects, strings in
3+1D. We argue how the condensate of such vortex strings must behave from the
known physics of the disordered superfluid, namely the Bose-Mott insulator. A
flaw in earlier proposals is repaired, and a more direct viewpoint, avoiding
gauge fields, in terms of the physical supercurrent is laid out, that also
easily generalizes to higher-dimensional and more complicated systems.
\\ ( http://arxiv.org/abs/1006.2267 , 40kb)
Date: Fri, 11 Jun 2010 14:43:22 GMT (229kb)

Title: Self-localization of a small number of Bose particles in a superfluid
   Fermi system
Authors: Krzysztof Sacha, Katarzyna Targo\'nska
Categories: cond-mat.quant-gas
Comments: 7 pages, 7 fiqures
   We consider self-localization of a small number of Bose particles immersed in
a large homogeneous superfluid mixture of fermions in three and one dimensional
spaces. Bosons the distort density of surrounding fermions and create a
potential well where they can form a bound state analogous to a small polaron
state. In the three dimensional volume we observe the self-localization for
repulsive interactions between bosons and fermions. In the one dimensional case
bosons self-localize as well as for attractive interactions forming, together
with a pair of fermions at the bottom of the Fermi sea, a vector soliton. We
analyze also thermal effects and show that small non-zero temperature affects
the pairing function of the Fermi-subsystem and has little influence on the
self-localization phenomena.
\\ ( http://arxiv.org/abs/1006.2324 , 229kb)
Date: Fri, 11 Jun 2010 18:10:41 GMT (227kb)

Title: Atomic Bloch-Zener Oscillations and St\"uckelberg Interferometry in
   Optical Lattices
Authors: Sebastian Kling, Tobias Salger, Christopher Grossert, and Martin Weitz
Categories: cond-mat.quant-gas
   We report on experiments investigating quantum transport and band
interferometry of an atomic Bose-Einstein condensate in an optical lattice with
a two-band miniband structure, realized with a Fourier-synthesized optical
lattice potential. Bloch-Zener oscillations, the coherent superposition of
Bloch oscillations and Landau-Zener tunneling between the two bands are
observed. When the relative phase between paths in different bands is varied,
an interference signal is observed, demonstrating the coherence of the dynamics
in the miniband system. Measured fringe patterns of this St\"uckelberg
interferometer allow to interferometrically map out the band structure of the
optical lattice over the full Brillouin zone.
\\ ( http://arxiv.org/abs/1006.2358 , 227kb)
Date: Fri, 11 Jun 2010 20:12:28 GMT (81kb,D)

Title: Efimov Physics in Atom-Dimer Scattering of Lithium-6 Atoms
Authors: H.-W. Hammer, Daekyoung Kang and Lucas Platter
Categories: cond-mat.quant-gas nucl-th
Comments: 13 pages, 5 figures
Report-no: HISKP-TH-10-14, INT-PUB-10-024
   Lithium-6 atoms in the three lowest hyperfine states display universal
properties when the S-wave scattering length between each pair of states is
large. Recent experiments reported four pronounced features arising from Efimov
physics in the atom-dimer relaxation rate, namely two resonances and two local
minima. We use the universal effective field theory to calculate the atom-dimer
relaxation rate at zero temperature. Our results describe the four features
qualitatively and imply there is a hidden local minimum. In the vicinity of the
resonance at 685 G, we perform a finite temperature calculation which improves
the agreement of theory and experiment. We conclude that finite temperature
effects cannot be neglected in the analysis of the experimental data.
\\ ( http://arxiv.org/abs/1006.2393 , 81kb)
arXiv:1006.2548 (*cross-listing*)
Date: Sun, 13 Jun 2010 17:17:15 GMT (274kb)

Title: Fermion Condensate and Vacuum Current Density Induced by Homogeneous and
   Inhomogeneous Magnetic Fields in (2+1)-Dimensions
Authors: Alfredo Raya and Edward Reyes
Categories: hep-ph cond-mat.supr-con hep-th math-ph math.MP
Comments: 8 pages, 2 figures. Accepted for publication in Phys. Rev. D
   We calculate the condensate and the vacuum current density induced by
external static magnetic fields in (2+1)-dimensions. At the perturbative level,
we consider an exponentially decaying magnetic field along one cartesian
coordinate. Non-perturbatively, we obtain the fermion propagator in the
presence of a uniform magnetic field by solving the Schwinger-Dyson equation in
the rainbow-ladder approximation. In the large flux limit, we observe that both
these quantities, either perturbative (inhomogeneous) and non-perturbative
(homogeneous), are proportional to the external field, in agreement with early
\\ ( http://arxiv.org/abs/1006.2548 , 274kb)
arXiv:1006.2556 (*cross-listing*)
Date: Sun, 13 Jun 2010 19:33:44 GMT (326kb)

Title: Dynamical studies of macroscopic superposition states: Phase engineering
   of novel controlled entangled number states of the gaseous atomic
   Bose-Einstein condensate in multiple wells
Authors: Mary Ann Leung, Khan W. Mahmud, William P. Reinhardt
Categories: cond-mat.quant-gas quant-ph
Comments: 9 pages, 11 figures
   We provide a scheme for the generation of entangled number states of
Bose-Einstein condensates in multiple wells with cyclic pairwise connectivity.
The condensate ground state in a multiple well trap can self-evolve, when phase
engineered with specific initial phase differences between the neighboring
wells, to a state with controllable entanglement. We demonstrate through
numerical simulations the creation of entangled states in three and four wells
and then explore the creation of "larger" entangled states where there are
either a larger number of particles in each well or a larger number of wells.
The type of entanglement produced as the particle numbers, or interaction
strength, increases changes in a novel and initially unexpected manner.
\\ ( http://arxiv.org/abs/1006.2556 , 326kb)
Date: Mon, 14 Jun 2010 09:22:35 GMT (4329kb)

Title: Macroscopic Rabi-Like Oscillations of Ultracold Atoms in an Asymmetrical
   Two-Dimensional Magnetic Lattice
Authors: A. Abdelrahman, M. Vasiliev and K. Alameh
Categories: quant-ph cond-mat.quant-gas
   We investigate the existence of the $macroscopic$ $quantum$ $phase$ in
trapped ultracold quantum degenerate gases, such as Bose-Einstein condensate,
in an asymmetrical two-dimensional magnetic lattice. We show the key to
adiabatically control the tunneling in the new two-dimensional magnetic lattice
by means of external magnetic bias fields. The macroscopic quantum phase
signature is identified as a Rabi-like oscillation when solving the system of
coupled time-dependent differential equations, described here by the Boson
Josephson Junctions (BJJs). In solving the system of the BJJs we used an order
parameter that includes both time-dependent variational parameters which are
the fractional population at each lattice site and the phase difference. The
BJJs solution presents a clear evidence for the macroscopic quantum coherence.
\\ ( http://arxiv.org/abs/1006.2645 , 4329kb)
arXiv:1006.2646 (*cross-listing*)
Date: Mon, 14 Jun 2010 09:24:21 GMT (81kb)

Title: Crossover in the Efimov spectrum
Authors: Ludovic Pricoupenko (LPTMC)
Categories: cond-mat.quant-gas quant-ph
   A filtering method is introduced for solving the zero-range three-boson
problem. This scheme allows one to solve the original Skorniakov and Ter
Martirosian integral equation for an arbitrary large Ultra-Violet cut-off and
to avoid the Thomas collapse of the three particles. The method is applied to a
more general zero-range model including a finite background two-body scattering
length and the effective range. A cross-over in the Efimov spectrum is found in
such systems and a specific regime emerges where Efimov states are long-lived.
\\ ( http://arxiv.org/abs/1006.2646 , 81kb)
Date: Mon, 14 Jun 2010 10:14:45 GMT (5kb)

Title: Weak Equivalence Principle and Propagation of the Wave Function in
   Quantum Mechanics
Authors: Clovis Jacinto de Matos
Categories: physics.gen-ph quant-ph
Comments: 3 pages
   The propagation of the wave function of a particle is characterised by a
group and a phase velocity. The group velocity is associated with the
particle's classical velocity, which is always smaller than the speed of light,
and the phase velocity is associated with the propagation speed of the wave
function phase and is treated as being unphysical, since its value is always
greater than the speed of light. Here we show, using Sciama's Machian
formulation of rest mass energy, that this physical interpretation, for the
group and the phase velocity of the wave function, is only valid if the weak
equivalence principle strictly holds for the propagating particle, except for
the photon. In case this constraint is released the phase velocity of the wave
function could acquire a physical meaning in quantum condensates.
\\ ( http://arxiv.org/abs/1006.2657 , 5kb)
arXiv:1006.2716 (*cross-listing*)
Date: Mon, 14 Jun 2010 14:04:45 GMT (861kb)

Title: Quantum Monte Carlo simulations of antiferromagnetism in ultracold
   fermions on optical lattices within real-space dynamical mean-field theory
Authors: N. Bl\"umer and E. V. Gorelik
Categories: cond-mat.quant-gas physics.comp-ph
Comments: 4 pages, 4 figures; proceedings of the Conference on Computational
   Physics 2009
   We present a massively parallel quantum Monte Carlo based implementation of
real-space dynamical mean-field theory for general inhomogeneous correlated
fermionic lattice systems. As a first application, we study magnetic order in a
binary mixture of repulsively interacting fermionic atoms harmonically trapped
in an optical lattice. We explore temperature effects and establish signatures
of the N\'{e}el transition in observables directly accessible in cold-atom
experiments; entropy estimates are also provided. We demonstrate that the local
density approximation (LDA) fails for ordered phases. In contrast, a "slab"
approximation allows us to reach experimental system sizes with O(10^5) atoms
without significant loss of accuracy.
\\ ( http://arxiv.org/abs/1006.2716 , 861kb)
Date: Tue, 15 Jun 2010 08:38:31 GMT (596kb)

Title: Dynamics of Vortices and Solitons in a Bose-Einstein Condensate by an
   Oscillating Potential
Authors: Kazuya Fujimoto and Makoto Tsubota
Categories: cond-mat.quant-gas
Comments: 8 pages, 6 figure
   We study numerically the dynamics of quantized vortices and solitons induced
by an oscillating potential inside a trapped Bose-Einstein condensate. The
dynamics of the topological defects is much different from the case for a
linear uniform object; the metamorphosis between vortices and solitons is
characteristic of the dynamics. We discuss how vortices are nucleated by an
oscillating potential.
\\ ( http://arxiv.org/abs/1006.2922 , 596kb)
Date: Tue, 15 Jun 2010 09:30:20 GMT (344kb)

Title: Fractalization and emission of vortex rings in the Kelvin waves cascade
Authors: Andrew W. Baggaley, Carlo F. Barenghi
Categories: cond-mat.stat-mech physics.flu-dyn
Comments: 18 pages, 12 figures
   We report results of numerical simulations of the time evolution of quantized
vortex filaments following a vortex reconnection. We study the resulting Kelvin
waves cascade and compare the amplitude spectrum with existing theories and
numerical calculations. We show that the vortex filaments become fractal, and
that large-amplitude twisting of the filaments leads to secondary reconnections
and the emission of small vortex rings.
\\ ( http://arxiv.org/abs/1006.2934 , 344kb)
arXiv:1006.2954 (*cross-listing*)
Date: Tue, 15 Jun 2010 10:46:21 GMT (960kb)

Title: Particle-Localized Ground State of Atom-Molecule Bose-Einstein
   Condensates in a Double-Well Potential
Authors: Atsushi Motohashi and Tetsuro Nikuni
Categories: cond-mat.quant-gas quant-ph
Comments: 34 pages,10 figures
   We study the effect of atom-molecule internal tunneling on the ground state
of atom-molecule Bose-Einstein condensates in a double-well potential. In the
absence of internal tunneling between atomic and molecular states, the ground
state is symmetric, which has equal-particle populations in two wells. From the
linear stability analysis, we show that the symmetric stationary state becomes
dynamically unstable at a certain value of the atom-molecule internal tunneling
strength. Above the critical value of the internal tunneling strength, the
ground state bifurcates to the particle-localized ground states. The origin of
this transition can be attributed to the effective attractive inter-atomic
interaction induced by the atom-molecule internal tunneling. This effective
interaction is similar to that familiar in the context of BCS-BEC crossover in
a Fermi gas with Feshbach resonance. Furthermore, we point out the possibility
of reentrant transition in the case of the large detuning between the atomic
and molecular states.
\\ ( http://arxiv.org/abs/1006.2954 , 960kb)
Date: Tue, 15 Jun 2010 11:21:41 GMT (1325kb)

Title: Rotonlike instability and pattern formation in spinor Bose-Einstein
Authors: Michal Matuszewski
Categories: cond-mat.quant-gas
   We show that metastable phases of an antiferromagnetic spin-1 condensate in a
simple model with pure contact interactions can exhibit a rotonlike minimum in
the excitation spectrum. The introduction of magnetic field gives rise to the
instability of roton modes, which can lead to spontaneous emergence of regular
periodic, polygonal, polyhedral or crystalline patterns, as shown in numerical
simulations within the truncated Wigner approximation. An explanation of the
occurrence of rotonlike instability is given based on the energy and spin
conservation laws.
\\ ( http://arxiv.org/abs/1006.2962 , 1325kb)
arXiv:1006.2975 (*cross-listing*)
Date: Tue, 15 Jun 2010 12:40:56 GMT (241kb,D)

Title: Cold atom simulation of interacting relativistic quantum field theories
Authors: J. Ignacio Cirac, Paolo Maraner and Jiannis K. Pachos
Categories: cond-mat.str-el hep-lat quant-ph
Comments: 4 pages, 3 figues
   We demonstrate that Dirac fermions self-interacting or coupled to dynamic
scalar fields can emerge in the low energy sector of designed bosonic and
fermionic cold atom systems. We illustrate this with two examples defined in
two spacetime dimensions. The first one is the self-interacting Thirring model.
The second one is a model of Dirac fermions coupled to a dynamic scalar field
that gives rise to the Gross-Neveu model. The proposed cold atom experiments
can be used to probe spectral or correlation properties of interacting quantum
field theories thereby presenting an alternative to lattice gauge theory
\\ ( http://arxiv.org/abs/1006.2975 , 241kb)
Date: Tue, 15 Jun 2010 14:21:54 GMT (86kb)

Title: Dynamical Density Fluctuation of Superfluids near Critical Velocities
Authors: Yusuke Kato and Shohei Watabe
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 4 pages, 1figure
   We propose a stability criterion of superfluids in condensed Bose-Einstein
systems, which incorporates the spectral function or the autocorrelation
function of the local density. Within the Gross-Pitaevskii-Bogoliubov theory,
we demonstrate the validity of our criterion for the soliton-emission
instability, with use of explicit forms of zero modes of the Bogoliubov
equation and a dynamical scaling near the saddle-node bifurcation. We also show
that the criterion is applicable to the Landau phonon instability and the
Landau roton instability within the single-mode approximation.
\\ ( http://arxiv.org/abs/1006.2999 , 86kb)
Date: Tue, 15 Jun 2010 14:42:52 GMT (267kb)

Title: The approach to vortex reconnection
Authors: Richard Tebbs, Anthony J. Youd, and Carlo F. Barenghi
Categories: cond-mat.quant-gas
Comments: 11 pages, 9 figures
   We present numerical solutions of the Gross--Pitaevskii equation
corresponding to reconnecting vortex lines. We determine the separation of
vortices as a function of time during the approach to reconnection, and study
the formation of pyramidal vortex structures. Results are compared with
analytical work and numerical studies based on the vortex filament method.
\\ ( http://arxiv.org/abs/1006.3004 , 267kb)
Date: Tue, 15 Jun 2010 15:05:25 GMT (38kb)

Title: Ultracold RbSr molecules can be formed by magnetoassociation
Authors: Piotr S. Zuchowski, J. Aldegunde and Jeremy M. Hutson
Categories: physics.atom-ph
Comments: 5 pages, 2 figures
   We investigate the interactions between ultracold alkali metal atoms and
closed-shell atoms using electronic structure calculations on the prototype
system Rb+Sr. There are molecular bound states that can be tuned across atomic
thresholds with magnetic field, and there are previously neglected terms in the
collision Hamiltonian that can produce zero-energy Feshbach resonances with
significant widths. The largest effect comes from the interaction-induced
variation of the Rb hyperfine coupling. The resonances may be used to form
paramagnetic polar molecules if the magnetic field can be controlled precisely
\\ ( http://arxiv.org/abs/1006.3006 , 38kb)
Date: Tue, 15 Jun 2010 16:27:07 GMT (200kb)

Title: Josephson tunneling of dark solitons in a double-well potential
Authors: H. Susanto, J. Cuevas, P. Kruger
Categories: cond-mat.quant-gas nlin.PS
Comments: 4 pages, submitted
   The dynamics of a quasi one-dimensional Bose-Einstein condensate in a double
well potential, modelled by an effectively one-dimensional nonlinear
Schrodinger equation, is studied. When a dark soliton is loaded into one of the
wells, it is shown that the soliton can tunnel between them experiencing the
physics known for electrons in a Josephson junction, or be self-trapped. A
coupled-mode approximation is derived to explain the observations. As dark
solitons are non-ground state excitations, numerical stability analysis based
on the full equation is necessary, where it is shown that such tunneling when
occurs can be stable. Through path following methods, unstable tunnelings are
also obtained. Finally, we outline an experimental scheme designed to explore
such dark soliton dynamics in the laboratory.
\\ ( http://arxiv.org/abs/1006.3024 , 200kb)
Date: Tue, 15 Jun 2010 17:30:53 GMT (158kb)

Title: Creation of NOON states by double Fock-state/Bose-Einstein condensates
Authors: W. J. Mullin \and F. Lalo\"{e}
Categories: quant-ph
Comments: 8 pages 5 figures
   NOON states (states of the form $|N>_{a}|0>_{b}+|0>_{a}|N>_{b}$ where $a$ and
$b$ are single particle states) have been used for predicting violations of
hidden-variable theories (Greenberger-Horne-Zeilinger violations) and are
valuable in metrology for precision measurements of phase at the Heisenberg
limit. We show theoretically how the use of two Fock state/Bose-Einstein
condensates as sources in a modified Mach Zender interferometer can lead to the
creation of the NOON state in which $a$ and $b$ refer to arms of the
interferometer and $N$ is the total number of particles in the two condensates.
The modification of the interferometer involves making conditional ``side''
measurements of a few particles near the sources. These measurements put the
remaining particles in a superposition of two phase states, which are converted
into NOON states by a beam splitter. The result is equivalent to the quantum
experiment in which a large molecule passes through two slits. The NOON states
are combined in a final beam splitter and show interference. Attempts to detect
through which ``slit'' the condensates passed destroys the interference.
\\ ( http://arxiv.org/abs/1006.3038 , 158kb)
Date: Tue, 15 Jun 2010 19:49:25 GMT (258kb)

Title: Non-classical Rotational Inertia in a Two-dimensional Bosonic Solid
   Containing Grain Boundaries
Authors: Chandan Dasgupta and Oriol T. Valls
Categories: cond-mat.quant-gas
Comments: Ten pages, including figures
   We study the occurrence of non-classical rotational inertia (NCRI) arising
from superfluidity along grain boundaries in a two-dimensional bosonic system.
We make use of a standard mapping between the zero-temperature properties of
this system and the statistical mechanics of interacting vortex lines in the
mixed phase of a type-II superconductor. In the mapping, the liquid phase of
the vortex system corresponds to the superfluid bosonic phase. We consider
numerically obtained polycrystalline configurations of the vortex lines in
which the microcrystals are separated by liquid-like grain boundary regions
which widen as the vortex system temperature increases. The NCRI of the
corresponding zero-temperature bosonic systems can then be numerically
evaluated by solving the equations of superfluid hydrodynamics in the channels
near the grain boundaries. We find that the NCRI increases very abruptly as the
liquid regions in the vortex system (equivalently, superfluid regions in the
bosonic system) form a connected, system-spannig structure with one or more
closed loops. The implications of these results for experimentally observed
supersolid phenomena are discussed.
\\ ( http://arxiv.org/abs/1006.3063 , 258kb)
Date: Tue, 15 Jun 2010 19:57:16 GMT (76kb)

Title: Exact dynamics of two cold bosons in a harmonic trap
Authors: Tomasz Sowinski, Miroslaw Brewczyk, Mariusz Gajda, Kazimierz Rzazewski
Categories: quant-ph cond-mat.quant-gas
Comments: 9 figures
   We study dynamics of two interacting ultra cold Bose atoms in a harmonic
oscillator potential in one spatial dimension. Making use of the exact solution
of the eigenvalue problem of a particle in the delta-like potential we study a
time evolution of some particularly chosen initial states, all being a two-fold
product of identical states of both particles. The corresponding time dependent
single particle density matrix is obtained and diagonalized and single particle
orbitals are found. The evolution of the orbital corresponding to the largest
eigenvalue is then compared to the evolution given by the Gross-Pitaevskii
equation. We show that if initially the center of mass and relative degrees of
freedom are entangled then the Gross-Pitaevskii equation fails to reproduce the
exact dynamics. We stress that predictions of our study can be verified
experimentally in an optical lattice in the low-tunneling limit when two atoms
occupy each lattice site.
\\ ( http://arxiv.org/abs/1006.3067 , 76kb)
Date: Wed, 16 Jun 2010 11:18:09 GMT (161kb)

Title: Turbulent superfluid profiles in a counterflow channel
Authors: L. Galantucci, C.F. Barenghi, M. Sciacca, M. Quadrio, and P. Luchini
Categories: cond-mat.other
Comments: 3 double figures, 9 pages
   We have developed a two-dimensional model of quantised vortices in helium II
moving under the influence of applied normal fluid and superfluid in a
counterflow channel. We predict superfluid and vortex-line density profiles
which could be experimentally tested using recently developed visualization
\\ ( http://arxiv.org/abs/1006.3183 , 161kb)
Date: Wed, 16 Jun 2010 13:24:46 GMT (155kb)

Title: Effective merging dynamics of two and three fluid vortices: Application
   to two-dimensional decaying turbulence
Authors: Cl\'ement Sire, Pierre-Henri Chavanis, and Julien Sopik
Categories: cond-mat.stat-mech physics.flu-dyn
Comments: 4 pages; 3 figures
   We present a kinetic theory of two-dimensional decaying turbulence in the
context of two-body and three-body vortex merging processes. By introducing the
equations of motion for two or three vortices in the effective noise due to all
the other vortices, we demonstrate analytically that a two-body mechanism
becomes inefficient at low vortex density $n\ll 1$. When the more efficient
three-body vortex mergings are considered, we show that $n\sim t^{-\xi}$, with
$\xi=1$. We generalize this argument to three-dimensional geostrophic
turbulence, finding $\xi=5/4$, in excellent agreement with direct Navier-Stokes
simulations [J.\,C. McWilliams \emph{et al.}, J. Fluid Mech. {\bf 401}, 1
\\ ( http://arxiv.org/abs/1006.3206 , 155kb)
Date: Wed, 16 Jun 2010 13:44:15 GMT (254kb,D)

Title: Interactions Between Rydberg-Dressed Atoms
Authors: J. E. Johnson and S. L. Rolston
Categories: physics.atom-ph quant-ph
Comments: 5 pages, 7 figures
   We examine interactions between atoms continuously and coherently driven
between the ground state and a Rydberg state, producing "Rydberg-dressed
atoms." Because of the large dipolar coupling between two Rydberg atoms, a
small admixture of Rydberg character into a ground state can produce an atom
with a dipole moment of a few Debye, the appropriate size to observe
interesting dipolar physics effects in cold atom systems. We have calculated
the interaction energies for atoms that interact via the dipole-dipole
interaction and find that due to blockade effects, the R-dependent two-atom
interaction terms are limited in size, and can be R-independent up until the
dipolar energy is equal to the detuning. This produces R-dependent interactions
different from the expected 1/R^3 dipolar form, which have no direct analogy in
condensed matter physics, and could lead to new quantum phases in trapped
Rydberg systems.
\\ ( http://arxiv.org/abs/1006.3212 , 254kb)
Date: Wed, 16 Jun 2010 14:48:36 GMT (124kb)

Title: Hysteresis effects in Bose-Einstein condensates
Authors: Andrea Sacchetti
Categories: quant-ph cond-mat.quant-gas
Comments: 10 pages, 2 figures
   Here, we consider damped two-components Bose-Einstein condensates with
many-body interactions. We show that, when the external trapping potential has
a double-well shape and when the nonlinear coupling factors are modulated in
time, hysteresis effects may appear under some circumstances. Such hysteresis
phenomena are a result of the joint contribution between the appearance of
saddle node bifurcations and damping effect.
\\ ( http://arxiv.org/abs/1006.3240 , 124kb)
Date: Wed, 16 Jun 2010 16:08:36 GMT (336kb)

Title: Ultracold atoms in a cavity mediated double-well system
Authors: Jonas Larson and Jani-Petri Martikainen
Categories: quant-ph cond-mat.quant-gas
Comments: 11 pages, 10 figures
   We study ground state properties and dynamics of a dilute ultracold atomic
gas in a double well potential. The Gaussian barrier separating the two wells
derives from the interaction between the atoms and a quantized field of a
driven Fabry-Perot cavity. Due to intrinsic atom-field nonlinearity, several
novel phenomena arise being the focus of this work. For the ground state, there
is a critical pumping amplitude in which the atoms self-organize and the intra
cavity field amplitude drastically increases. In the dynamical analysis, we
show that the Josephson oscillations depend strongly on the atomic density and
may be greatly suppressed within certain regimes, reminiscent of self-trapping
of Bose-Einstein condensates in double-well setups. This pseudo self-trapping
effect is studied within a mean-field treatment valid for large atom numbers.
For small numbers of atoms, we consider the analogous many-body problem and
demonstrate a collapse-revival structure in the Josephson oscillations.
\\ ( http://arxiv.org/abs/1006.3258 , 336kb)
Date: Wed, 16 Jun 2010 21:28:41 GMT (161kb)

Title: Non-thermal equilibration of a one-dimensional Fermi gas
Authors: Matthias Kronenwett and Thomas Gasenzer
Categories: cond-mat.quant-gas cond-mat.stat-mech hep-ph
Comments: 4 pages, 4 figures
   Equilibration of an isolated Fermi gas in one spatial dimension after an
interaction quench is studied. Evaluating Kadanoff-Beym dynamic equations for
correlation functions obtained from the two-particle-irreducible effective
action in nonperturbative approximation, the gas is seen to evolve to states
characterized by thermal as well as nonthermal momentum distributions,
depending on the assumed initial conditions. For total energies near the Fermi
temperature, stationary power laws emerge for the high-momentum tails while at
lower momenta the distributions are of Fermi-Dirac type. The relation found
between fluctuations and dissipation exhibits nonthermal final states.
\\ ( http://arxiv.org/abs/1006.3330 , 161kb)
Date: Thu, 17 Jun 2010 08:46:18 GMT (40kb)

Title: Pseudogap Phase and Remnant Fermi Surface in Ultracold Fermi Gases
Authors: A. Perali, P. Pieri, F. Palestini, G. C. Strinati, J. T. Stewart, J.
   P. Gaebler, T. E. Drake, D. S. Jin
Categories: cond-mat.quant-gas
Comments: 6 pages, 6 figures
   Wave-vector resolved radio frequency (rf) spectroscopy data for an ultracold
trapped Fermi gas are reported for several couplings at Tc, and extensively
analyzed in terms of a pairing-fluctuation theory. This combined analysis shows
that the strongly non-Fermi-liquid behavior associated with the presence of a
pseudogap coexists with a robust remnant Fermi surface over a wide coupling
range, which in turn sets the boundary of the pseudogap phase.
\\ ( http://arxiv.org/abs/1006.3406 , 40kb)
Date: Thu, 17 Jun 2010 13:29:57 GMT (22kb,D)

Title: On the bosonic behavior of mean-field fluctuations in atomic ensembles
Authors: Michael Keyl and Dirk-Michael Schlingemann and Zoltan Zimboras
Categories: quant-ph
Comments: 19 pages
   The mean field fluctuations of large atomic ensembles can behave like bosonic
modes, i.e. they induce a state on an appropriate system of bosonic modes. The
most prominent example is that, if the atomic ensemble is in a homogenous
product state, then the mean-field fluctuations are inducing a Gaussian state
on a system of bosonic modes. In the present paper we show that for atomic
ensemble states with exponentially decaying correlations (e.g. with respect to
the distance of atoms) the mean-field fluctuations are inducing (possibly
non-Gaussian) states on the on a system of bosonic modes. This result is true
for a general lattice of atomic systems that is equipped with a reasonable
distance function.
\\ ( http://arxiv.org/abs/1006.3461 , 22kb)
arXiv:1006.3466 (*cross-listing*)
Date: Thu, 17 Jun 2010 13:44:30 GMT (67kb)

Title: Collective atomic recoil motion in short-pulse multi-matter-optical wave
Authors: L. Deng and E.W. Hagley
Categories: cond-mat.quant-gas quant-ph
Comments: This manuscript was submitted for publication in Nov., 2009
   An analytical perturbation theory of short-pulse, matter-wave superradiant
scatterings is presented. We show that Bragg resonant enhancement is
incapacitated and both positive and negative order scatterings contribute
equally. We further show that propagation gain is small and scattering events
primarily occur at the end of the condensate where the generated field has
maximum strength, thereby explaining the apparent ``asymmetry" in the scattered
components with respect to the condensate center. In addition, the generated
field travels near the speed of light in a vacuum, resulting in significant
spontaneous emission when the one-photon detuning is not sufficiently large.
Finally, we show that when the excitation rate increases, the generated-field
front-edge-steepening and peak forward-shifting effects are due to depletion of
the ground state matter wave.
\\ ( http://arxiv.org/abs/1006.3466 , 67kb)
Date: Thu, 17 Jun 2010 18:26:13 GMT (743kb)

Title: Femtosecond Quasiparticle and Phonon Dynamics in Superconducting
   YBa2Cu3O7 Studied by Wideband Terahertz Spectroscopy
Authors: A. Pashkin, M. Porer, M. Beyer, K. W. Kim, A. Dubroka, C. Bernhard, X.
   Yao, Y. Dagan, R. Hackl, A. Erb, J. Demsar, R. Huber, and A. Leitenstorfer
Categories: cond-mat.supr-con
Comments: 4 pages, 4 figures
   We measure the anisotropic mid-infrared response of electrons and phonons in
bulk YBa2Cu3O7 after femtosecond photoexcitation. A line shape analysis of
specific lattice modes reveals their transient occupation and coupling to the
superconducting condensate. The apex oxygen vibration is strongly excited
within 150\,fs demonstrating that the lattice absorbs a major portion of the
pump energy before the quasiparticles are thermalized. Our results attest to
substantial electron-phonon scattering and introduce a powerful concept probing
electron-lattice interactions in a variety of complex materials.
\\ ( http://arxiv.org/abs/1006.3539 , 743kb)
Date: Thu, 17 Jun 2010 19:17:11 GMT (1500kb,D)

Title: Dynamics of a tunable superfluid junction
Authors: L. J. LeBlanc, A. B. Bardon, J. McKeever, M. H. T. Extavour, D.
   Jervis, J. H. Thywissen, F. Piazza and A. Smerzi
Categories: cond-mat.quant-gas
Comments: 7 pages, 6 figures
   We study the population dynamics of a Bose-Einstein condensate in a
double-well potential with tunable barrier height. In the regime of weak
inter-well coupling, we observe Josephson plasma oscillations as expected.
However, in the strong-coupling regime, a second frequency enters the dynamics.
We explain the amplitude, frequency, and nature of these two modes by with
Gross-Pitaevskii calculations throughout the weak- to strong-coupling
crossover. Our results interpolate between two standard paradigms of
superfluidity: hydrodynamics and Josephson dynamics.
\\ ( http://arxiv.org/abs/1006.3550 , 1500kb)

The replacements:

replaced with revised version Fri, 11 Jun 2010 03:51:54 GMT (90kb,D)

Title: Semiclassical dynamics of quasi-one-dimensional, attractive
   Bose-Einstein condensates
Authors: Alexander Tovbis and Mark A. Hoefer
Categories: cond-mat.quant-gas
Comments: 8 pages, 2 figures
\\ ( http://arxiv.org/abs/1006.1438 , 90kb)
replaced with revised version Fri, 11 Jun 2010 09:52:04 GMT (34kb)

Title: The Universality and stability for a dilute Bose gas with a Feshbach
Authors: Yu-Li Lee and Yu-Wen Lee
Categories: cond-mat.quant-gas cond-mat.other
Comments: 6 pages, 4 figures
Journal-ref: Phys. Rev. A 81, 063613 (2010)
\\ ( http://arxiv.org/abs/1001.2592 , 34kb)
replaced with revised version Mon, 14 Jun 2010 10:02:04 GMT (1464kb,D)

Title: Fermionic Projected Entangled Pair States
Authors: Christina V. Kraus, Norbert Schuch, Frank Verstraete, J. Ignacio Cirac
Categories: quant-ph cond-mat.other
Comments: 7 pages, 3 figures
Journal-ref: Phys. Rev. A 81, 052338 (2010)
DOI: 10.1103/PhysRevA.81.052338
\\ ( http://arxiv.org/abs/0904.4667 , 1464kb)
replaced with revised version Tue, 15 Jun 2010 09:03:40 GMT (2075kb)

Title: Population and mass imbalance in atomic Fermi gases
Authors: J.E. Baarsma, K.B. Gubbels, H.T.C. Stoof
Categories: cond-mat.quant-gas
Comments: 17 pages, 17 figures
\\ ( http://arxiv.org/abs/0912.4205 , 2075kb)
replaced with revised version Tue, 15 Jun 2010 11:35:38 GMT (69kb,D)

Title: Ground-state properties of few dipolar bosons in a quasi-one-dimensional
   harmonic trap
Authors: Frank Deuretzbacher, Jonas C. Cremon, Stephanie M. Reimann
Categories: cond-mat.quant-gas cond-mat.other
Journal-ref: Phys. Rev. A 81, 063616 (2010)
DOI: 10.1103/PhysRevA.81.063616
\\ ( http://arxiv.org/abs/0909.1192 , 69kb)
replaced with revised version Wed, 16 Jun 2010 10:43:15 GMT (94kb,D)

Title: Decay of polarons and molecules in a strongly polarized Fermi gas
Authors: G. M. Bruun, P. Massignan
Categories: cond-mat.quant-gas
Comments: Version accepted in PRL. Added discussion of three-body losses to
   deeply bound molecular states
\\ ( http://arxiv.org/abs/1003.5667 , 94kb)
replaced with revised version Thu, 17 Jun 2010 01:35:12 GMT (1147kb,D)

Title: Topological quantum phase transitions of attractive spinless fermions in
   a honeycomb lattice
Authors: Dario Poletti, Christian Miniatura and Benoit Gremaud
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/1006.3179 , 1147kb)
replaced with revised version Thu, 17 Jun 2010 03:45:28 GMT (42kb)

Title: Universal four-component Fermi gas in one dimension
Authors: Yusuke Nishida and Dam T. Son
Categories: cond-mat.quant-gas nucl-th
Comments: 6 pages, 2 figures; (v2) Efimov effect for 5 bosons in 1D is
Report-no: MIT-CTP 4055, INT-PUB-09-038
\\ ( http://arxiv.org/abs/0908.2159 , 42kb)
arXiv:1006.3250 (*cross-listing*)
replaced with revised version Thu, 17 Jun 2010 14:44:39 GMT (836kb)

Title: Observation of collective atomic recoil motion in a momentum-squeezed,
   ultra-cold, degenerate fermion gas
Authors: Pengjun Wang, L. Deng, E.W. Hagley, Zhengkun Fu, and Shijie Chai, Jing
Categories: cond-mat.quant-gas quant-ph
\\ ( http://arxiv.org/abs/1006.3250 , 836kb)

Till next time,

Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           www.physics.uq.edu.au/people/mdavis/
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