210 research outputs found
Feshbach resonances in mixtures of ultracold Li and Rb gases
We report on the observation of two Feshbach resonances in collisions between
ultracold Li and Rb atoms in their respective hyperfine ground
states and . The resonances show up as trap losses
for the Li cloud induced by inelastic Li-Rb-Rb three-body collisions. The
magnetic field values where they occur represent important benchmarks for an
accurate determination of the interspecies interaction potentials. A broad
Feshbach resonance located at 1066.92 G opens interesting prospects for the
creation of ultracold heteronuclear molecules. We furthermore observe a strong
enhancement of the narrow p-wave Feshbach resonance in collisions of Li
atoms at 158.55 G in the presence of a dense Rb cloud. The effect of the
Rb cloud is to introduce Li-Li-Rb three-body collisions occurring at a
higher rate than Li-Li-Li collisions.Comment: 4 pages, 3 figure
Radiofrequency spectroscopy of Li p-wave molecules: towards photoemission spectroscopy of a p-wave superfluid
Understanding superfluidity with higher order partial waves is crucial for
the understanding of high- superconductivity. For the realization of a
superfluid with anisotropic order parameter, spin-polarized fermionic lithium
atoms with strong p-wave interaction are the most promising candidates to date.
We apply rf-spectroscopy techniques that do not suffer from severe final-state
effects \cite{Perali08} with the goal to perform photoemission spectroscopy on
a strongly interacting p-wave Fermi gas similar to that recently applied for
s-wave interactions \cite{Stewart08}. Radiofrequency spectra of both quasibound
p-wave molecules and free atoms in the vicinity of the p-wave Feshbach
resonance located at 159.15\,G \cite{Schunck05} are presented. The observed
relative tunings of the molecular and atomic signals in the spectra with
magnetic field confirm earlier measurements realized with direct rf-association
\cite{Fuchs08}. Furthermore, evidence of bound molecule production using
adiabatic ramps is shown. A scheme to observe anisotropic superfluid gaps, the
most direct proof of p-wave superfluidity, with 1d-optical lattices is
proposed.Comment: 5 pages, 3 figure
The Atomic Lighthouse Effect
We investigate the deflection of light by a cold atomic cloud when the
light-matter interaction is locally tuned via the Zeeman effect using magnetic
field gradients. This "lighthouse" effect is strongest in the single-scattering
regime, where deviation of the incident field is largest. For optically dense
samples, the deviation is reduced by collective effects, as the increase in
linewidth leads to a decrease of the magnetic field efficiency
Quantum-degenerate mixture of fermionic lithium and bosonic rubidium gases
We report on the observation of sympathetic cooling of a cloud of fermionic
6-Li atoms which are thermally coupled to evaporatively cooled bosonic 87-Rb.
Using this technique we obtain a mixture of quantum-degenerate gases, where the
Rb cloud is colder than the critical temperature for Bose-Einstein condensation
and the Li cloud colder than the Fermi temperature. From measurements of the
thermalization velocity we estimate the interspecies s-wave triplet scattering
length |a_s|=20_{-6}^{+9} a_B. We found that the presence of residual rubidium
atoms in the |2,1> and the |1,-1> Zeeman substates gives rise to important
losses due to inelastic collisions.Comment: 4 pages, 3 figure
Observation of Lasing Mediated by Collective Atomic Recoil
We observe the buildup of a frequency-shifted reverse light field in a
unidirectionally pumped high- optical ring cavity serving as a dipole trap
for cold atoms. This effect is enhanced and a steady state is reached, if via
an optical molasses an additional friction force is applied to the atoms. We
observe the displacement of the atoms accelerated by momentum transfer in the
backscattering process and interpret our observations in terms of the
collective atomic recoil laser. Numerical simulations are in good agreement
with the experimental results.Comment: 4 pages, 3 figure
Phase-sensitive detection of Bragg scattering at 1D optical lattices
We report on the observation of Bragg scattering at 1D atomic lattices. Cold
atoms are confined by optical dipole forces at the antinodes of a standing wave
generated by the two counter-propagating modes of a laser-driven high-finesse
ring cavity. By heterodyning the Bragg-scattered light with a reference beam,
we obtain detailed information on phase shifts imparted by the Bragg scattering
process. Being deep in the Lamb-Dicke regime, the scattered light is not
broadened by the motion of individual atoms. In contrast, we have detected
signatures of global translatory motion of the atomic grating.Comment: 4 pages, 4 figure
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