16 research outputs found
Structural phase transitions of vortex matter in an optical lattice
We consider the vortex structure of a rapidly rotating trapped atomic
Bose-Einstein condensate in the presence of a co-rotating periodic optical
lattice potential. We observe a rich variety of structural phases which reflect
the interplay of the vortex-vortex and vortex-lattice interactions. The lattice
structure is very sensitive to the ratio of vortices to pinning sites and we
observe structural phase transitions and domain formation as this ratio is
varied.Comment: 4 pages, 3 figure
Excitation spectroscopy of vortex lattices in a rotating Bose-Einstein condensate
Excitation spectroscopy of vortex lattices in rotating Bose-Einstein
condensates is described. We numerically obtain the Bogoliubov-deGenne
quasiparticle excitations for a broad range of energies and analyze them in the
context of the complex dynamics of the system. Our work is carried out in a
regime in which standard hydrodynamic assumptions do not hold, and includes
features not readily contained within existing treatments.Comment: 4 pages, 4 figures. Submitted for publicatio
Single Impurity In Ultracold Fermi Superfluids
The role of impurities as experimental probes in the detection of quantum
material properties is well appreciated. Here we study the effect of a single
classical magnetic impurity in trapped ultracold Fermi superfluids. Depending
on its shape and strength, a magnetic impurity can induce single or multiple
mid-gap bound states in a superfluid Fermi gas. The multiple mid-gap states
could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) phase within the superfluid. As an analog of the Scanning Tunneling
Microscope, we propose a modified RF spectroscopic method to measure the local
density of states which can be employed to detect these states and other
quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de
Gennes calculations is that a magnetic impurity can controllably induce an FFLO
state at currently accessible experimental parameters.Comment: 5 pages, 3 figures; added calculations for 3
Bogoliubov-de Gennes study of trapped spin-imbalanced unitary Fermi gases
It is quite common that several different phases exist simultaneously in a
system of trapped quantum gases of ultra-cold atoms. One such example is the
strongly-interacting Fermi gas with two imbalanced spin species, which has
received a great amount of attention due to the possible presence of exotic
superfluid phases. By employing novel numerical techniques and algorithms, we
self-consistently solve the Bogoliubov de-Gennes equations, which describe
Fermi superfluids in the mean-field framework. From this study, we investigate
the novel phases of spin-imbalanced Fermi gases and examine the validity of the
local density approximation (LDA), which is often invoked in the extraction of
bulk properties from experimental measurements within trapped systems. We show
how the validity of the LDA is affected by the trapping geometry, number of
atoms and spin imbalance.Comment: 15 pages, 5 figures, to be published in New J. Phys. (focus issue on
"Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to QCD
Plasmas"
Shape oscillation of a rotating Bose-Einstein condensate
We present a theoretical and experimental analysis of the transverse monopole
mode of a fast rotating Bose-Einstein condensate. The condensate's rotation
frequency is similar to the trapping frequency and the effective confinement is
only ensured by a weak quartic potential. We show that the non-harmonic
character of the potential has a clear influence on the mode frequency, thus
making the monopole mode a precise tool for the investigation of the fast
rotation regime
Excitation spectrum of vortex lattices in rotating Bose-Einstein condensates
Using the coarse grain averaged hydrodynamic approach, we calculate the
excitation spectrum of vortex lattices sustained in rotating Bose-Einstein
condensates. The spectrum gives the frequencies of the common-mode longitudinal
waves in the hydrodynamic regime, including those of the higher-order
compressional modes. Reasonable agreement with the measurements taken in a
recent JILA experiment is found, suggesting that one of the longitudinal modes
reported in the experiment is likely to be the , mode.Comment: 2 figures. Submitted to Physical Review A. v2 contains more
references. No change in the main resul
Feshbach resonances in
We describe s-wave collisions between ultracold
23Na and 87Rb atoms in the presence of a magnetic field.
For any collision input channel knowledge of the singlet and
triplet intermolecular potentials [CITE] enables us to
predict the variation in scattering lengths as a function of the
magnetic field. We employ the Born-Oppenheimer approximation to
predict several Feshbach resonances for 23Na87Rb. We
also include a discussion of why these resonances are expected to
be narrow as observed in the case of 87Rb2