742 research outputs found
Feshbach resonances in 3He*-4He* mixtures
We discuss the stability of homonuclear and heteronuclear mixtures of 3He and
4He atoms in the metastable 2^3S_1 state (He*) and predict positions and widths
of Feshbach resonances by using the Asymptotic Bound-state Model (ABM). All
calculations are performed without fit parameters, using \emph{ab-initio}
calculations of molecular potentials. One promising very broad Feshbach
resonance (\Delta B=72.9^{+18.3}_{-19.3} mT) is found that allows for tuning of
the inter-isotope scattering length.Comment: 12 pages, 7 figure
Asymptotic Bound-state Model for Feshbach Resonances
We present an Asymptotic Bound-state Model which can be used to accurately
describe all Feshbach resonance positions and widths in a two-body system. With
this model we determine the coupled bound states of a particular two-body
system. The model is based on analytic properties of the two-body Hamiltonian,
and on asymptotic properties of uncoupled bound states in the interaction
potentials. In its most simple version, the only necessary parameters are the
least bound state energies and actual potentials are not used. The complexity
of the model can be stepwise increased by introducing threshold effects,
multiple vibrational levels and additional potential parameters. The model is
extensively tested on the 6Li-40K system and additional calculations on the
40K-87Rb system are presented.Comment: 13 pages, 8 figure
Broad Feshbach resonance in the 6Li-40K mixture
We study the widths of interspecies Feshbach resonances in a mixture of the
fermionic quantum gases 6Li and 40K. We develop a model to calculate the width
and position of all available Feshbach resonances for a system. Using the model
we select the optimal resonance to study the 6Li/40K mixture. Experimentally,
we obtain the asymmetric Fano lineshape of the interspecies elastic cross
section by measuring the distillation rate of 6Li atoms from a potassium-rich
6Li/40K mixture as a function of magnetic field. This provides us with the
first experimental determination of the width of a resonance in this mixture,
Delta B=1.5(5) G. Our results offer good perspectives for the observation of
universal crossover physics using this mass-imbalanced fermionic mixture.Comment: 4 pages, 2 figure
Nanoplasmonic Lattices for Ultracold atoms
We propose to use sub-wavelength confinement of light associated with the
near field of plasmonic systems to create nanoscale optical lattices for
ultracold atoms. Our approach combines the unique coherence properties of
isolated atoms with the sub-wavelength manipulation and strong light-matter
interaction associated with nano-plasmonic systems. It allows one to
considerably increase the energy scales in the realization of Hubbard models
and to engineer effective long-range interactions in coherent and dissipative
many-body dynamics. Realistic imperfections and potential applications are
discussed.Comment: 5 pages, 3 figures, V2: minor changes, V3: minor changes, added
supplemental materia
Large atom number dual-species magneto-optical trap for fermionic 6Li and 40K atoms
We present the design, implementation and characterization of a dual-species
magneto-optical trap (MOT) for fermionic 6Li and 40K atoms with large atom
numbers. The MOT simultaneously contains 5.2x10^9 6Li-atoms and 8.0x10^9
40K-atoms, which are continuously loaded by a Zeeman slower for 6Li and a
2D-MOT for 40K. The atom sources induce capture rates of 1.2x10^9 6Li-atoms/s
and 1.4x10^9 40K-atoms/s. Trap losses due to light-induced interspecies
collisions of ~65% were observed and could be minimized to ~10% by using low
magnetic field gradients and low light powers in the repumping light of both
atomic species. The described system represents the starting point for the
production of a large-atom number quantum degenerate Fermi-Fermi mixture
Critical number of atoms in an attractive Bose-Einstein condensate on an optical plus harmonic traps
The stability of an attractive Bose-Einstein condensate on a joint
one-dimensional optical lattice and an axially-symmetric harmonic trap is
studied using the numerical solution of the time-dependent mean-field
Gross-Pitaevskii equation and the critical number of atoms for a stable
condensate is calculated. We also calculate this critical number of atoms in a
double-well potential which is always greater than that in an axially-symmetric
harmonic trap. The critical number of atoms in an optical trap can be made
smaller or larger than the corresponding number in the absence of the optical
trap by moving a node of the optical lattice potential along the axial
direction of the harmonic trap. This variation of the critical number of atoms
can be observed experimentally and compared with the present calculation.Comment: Latex with 7 eps figures, Accepted in Journal of Physics
Liberating Efimov physics from three dimensions
When two particles attract via a resonant short-range interaction, three
particles always form an infinite tower of bound states characterized by a
discrete scaling symmetry. It has been considered that this Efimov effect
exists only in three dimensions. Here we review how the Efimov physics can be
liberated from three dimensions by considering two-body and three-body
interactions in mixed dimensions and four-body interaction in one dimension. In
such new systems, intriguing phenomena appear, such as confinement-induced
Efimov effect, Bose-Fermi crossover in Efimov spectrum, and formation of
interlayer Efimov trimers. Some of them are observable in ultracold atom
experiments and we believe that this study significantly broadens our horizons
of universal Efimov physics.Comment: 17 pages, 5 figures, contribution to a special issue of Few-Body
Systems devoted to Efimov Physic
Exploring an ultracold Fermi-Fermi mixture: Interspecies Feshbach resonances and scattering properties of 6Li and 40K
We report on the observation of Feshbach resonances in an ultracold mixture
of two fermionic species, 6Li and 40K. The experimental data are interpreted
using a simple asymptotic bound state model and full coupled channels
calculations. This unambiguously assigns the observed resonances in terms of
various s- and p-wave molecular states and fully characterizes the ground-state
scattering properties in any combination of spin states.Comment: 4 pages, 4 figures, 1 tabl
Beam Test of Silicon Strip Sensors for the ZEUS Micro Vertex Detector
For the HERA upgrade, the ZEUS experiment has designed and installed a high
precision Micro Vertex Detector (MVD) using single sided micro-strip sensors
with capacitive charge division. The sensors have a readout pitch of 120
microns, with five intermediate strips (20 micron strip pitch). An extensive
test program has been carried out at the DESY-II testbeam facility. In this
paper we describe the setup developed to test the ZEUS MVD sensors and the
results obtained on both irradiated and non-irradiated single sided micro-strip
detectors with rectangular and trapezoidal geometries. The performances of the
sensors coupled to the readout electronics (HELIX chip, version 2.2) have been
studied in detail, achieving a good description by a Monte Carlo simulation.
Measurements of the position resolution as a function of the angle of incidence
are presented, focusing in particular on the comparison between standard and
newly developed reconstruction algorithms.Comment: 41 pages, 21 figures, 2 tables, accepted for publication in NIM
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