Experimental Study of the BEC-BCS Crossover Region in Lithium 6

Abstract

We report Bose-Einstein condensation of weakly bound ${}^6\mathrm{L}\mathrm{i}_2$ molecules in a crossed optical trap near a Feshbach resonance. We measure a molecule-molecule scattering length of ${170}_{-60}^{+100}\mathrm{n}\mathrm{m}$ at $770\mathrm{G}$, in good agreement with theory. We study the 2D expansion of the cloud and show deviation from hydrodynamic behavior in the BEC-BCS crossover region.