1,230 research outputs found
Expansion of a Fermi gas interacting with a Bose-Einstein condensate
We study the expansion of an atomic Fermi gas interacting attractively with a
Bose-Einstein condensate. We find that the interspecies interaction affects
dramatically both the expansion of the Fermi gas and the spatial distribution
of the cloud in trap. We observe indeed a slower evolution of the
radial-to-axial aspect ratio which reveals the importance of the mutual
attraction between the two samples during the first phase of the expansion. For
large atom numbers, we also observe a bimodal momentum distribution of the
Fermi gas, which reflects directly the distribution of the mixture in trap.
This effect allows us to extract information on the dynamics of the system at
the collapse.Comment: 4 pages, 4 figure
Dynamical instability and dispersion management of an attractive condensate in an optical lattice
We investigate the stability of an attractive Bose-Einstein condensate in a
moving 1D optical lattice in the presence of transverse confinement. By means
of a Bogoliubov linear stability analysis we find that the system is
dynamically unstable for low quasimomenta and becomes stable near the band
edge, in a specular fashion with respect to the repulsive case. For low
interactions the instability occurs via long wavelength excitations that are
not sufficient for spoiling the condensate coherence, producing instead an
oscillating density pattern both in real and momentum space. This behaviour is
illustrated by simulations for the expansion of the condensate in a moving
lattice.Comment: 5 pages, 4 figure
39-K Bose-Einstein condensate with tunable interactions
We produce a Bose-Einstein condensate of 39-K atoms. Condensation of this
species with naturally small and negative scattering length is achieved by a
combination of sympathetic cooling with 87-Rb and direct evaporation,
exploiting the magnetic tuning of both inter- and intra-species interactions at
Feshbach resonances. We explore tunability of the self-interactions by studying
the expansion and the stability of the condensate. We find that a 39-K
condensate is interesting for future experiments requiring a weakly interacting
Bose gas.Comment: 5 page
Control of the interaction in a Fermi-Bose mixture
We control the interspecies interaction in a two-species atomic quantum
mixture by tuning the magnetic field at a Feshbach resonance. The mixture is
composed by fermionic 40K and bosonic 87Rb. We observe effects of the large
attractive and repulsive interaction energy across the resonance, such as
collapse or a reduced spatial overlap of the mixture, and we accurately locate
the resonance position and width. Understanding and controlling instabilities
in this mixture opens the way to a variety of applications, including formation
of heteronuclear molecular quantum gases.Comment: 5 Page
Enhancement of the scissors mode of an expanding Bose-Einstein condensate
We study the time-evolution of the scissors mode of a Bose-Einstein
condensate during the ballistic expansion after release from the magnetic trap.
We show that despite the nontrivial character of the superfluid expansion, the
sinusoidal behavior of the scissor oscillations is recovered after an
asymptotic expansion, with an enhancement of the final amplitude. We
investigate this phenomenon with a condensate held in an elongated
magnetostatic potential, whose particular shape allows for the excitation of
the scissors mode.Comment: RevTeX, 5 figure
Observation of subdiffusion of a disordered interacting system
We study the transport dynamics of matter-waves in the presence of disorder
and nonlinearity. An atomic Bose-Einstein condensate that is localized in a
quasiperiodic lattice in the absence of atom-atom interaction shows instead a
slow expansion with a subdiffusive behavior when a controlled repulsive
interaction is added. The measured features of the subdiffusion are compared to
numerical simulations and a heuristic model. The observations confirm the
nature of subdiffusion as interaction-assisted hopping between localized states
and highlight a role of the spatial correlation of the disorder.Comment: 8 pages, to be published on Physical Review Letter
- …