293 research outputs found
Double species condensate with tunable interspecies interactions
We produce Bose-Einstein condensates of two different species, Rb and
K, in an optical dipole trap in proximity of interspecies Feshbach
resonances. We discover and characterize two Feshbach resonances, located
around 35 and 79 G, by observing the three-body losses and the elastic
cross-section. The narrower resonance is exploited to create a double species
condensate with tunable interactions. Our system opens the way to the
exploration of double species Mott insulators and, more in general, of the
quantum phase diagram of the two species Bose-Hubbard model.Comment: 4 pages, 4 figure
Association of ultracold double-species bosonic molecules
We report on the creation of heterospecies bosonic molecules, associated from
an ultracold Bose-Bose mixture of 41K and 87Rb, by using a resonantly modulated
magnetic field close to two Feshbach resonances. We measure the binding energy
of the weakly bound molecular states versus the Feshbach field and compare our
results to theoretical predictions. We observe the broadening and asymmetry of
the association spectrum due to thermal distribution of the atoms, and a
frequency shift occurring when the binding energy depends nonlinearly on the
Feshbach field. A simple model is developed to quantitatively describe the
association process. Our work marks an important step forward in the
experimental route towards Bose-Einstein condensates of dipolar molecules.Comment: 5 pages, 4 figure
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
Collisional properties of sympathetically cooled K
We report the experimental evidence of the sympathetic cooling of K
with Rb down to 1 K, obtained in a novel tight confining magnetic
trap. This allowed us to perform the first direct measurement of the elastic
cross section of K below 50 K. The result obtained for the triplet
scattering length, Bohr radii, agrees with previous results
derived from photoassociation spectra and from Feshbach spectroscopy of
K.Comment: 7 pages, 4 figures, submitted to Phys. Rev.
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
A strongly interacting gas of two-electron fermions at an orbital Feshbach resonance
We report on the experimental observation of a strongly interacting gas of
ultracold two-electron fermions with orbital degree of freedom and magnetically
tunable interactions. This realization has been enabled by the demonstration of
a novel kind of Feshbach resonance occurring in the scattering of two 173Yb
atoms in different nuclear and electronic states. The strongly interacting
regime at resonance is evidenced by the observation of anisotropic hydrodynamic
expansion of the two-orbital Fermi gas. These results pave the way towards the
realization of new quantum states of matter with strongly correlated fermions
with orbital degree of freedom.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
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