Expansion of a lithium gas in the BEC-BCS crossover

Abstract

We report on experiments in ${}^6$Li Fermi gases near Feshbach resonances. A broad s-wave resonance is used to form a Bose-Einstein condensate of weakly bound ${}^6$Li${}_2$ molecules in a crossed optical trap. The measured molecule-molecule scattering length of $170_{-60}^{+100}$ nm at 770 G is found in good agreement with theory. The expansion energy of the cloud in the BEC-BCS crossover region is measured. Finally we discuss the properties of p-wave Feshbach resonances observed near 200 Gauss and new s-wave resonances in the heteronuclear ${}^6$Li- ${}^7$Li mixture.

10 pages, 3 figures, Proceedings of ICAP 2004