Atomic Bose-Einstein condensate to molecular Bose-Einstein condensate transition*

We report the formation of Bose-Einstein condensates (BECs) of spinning molecules by inducing pairing interactions in an atomic condensate near a g−wave Feshbach resonance. The trap geometry and the low temperature of the molecules help reducing inelastic loss to ensure thermal equilibrium. From the equation of state measurement, we determine the molecular scattering length to be +220(30) Bohr. We also investigate the unpairing dynamics and find that near the resonance the dynamical time scale is consistent with the unitarity limit. Our work confirms the long-sought transition between atomic and molecular condensates, the bosonic analog of the BEC-BCS (Bardeen-Cooper-Schrieffer superfluid) crossover in a Fermi gas. In addition, our experiment may shed light on condensed pairs with orbital angular momentum, where novel anisotropic superfluid with non-zero surface current is predicted for, e.g., ³He-A.