Decay of an Ultracold Fermionic Lithium Gas near a Feshbach Resonance

Abstract

We studied the magnetic field dependence of the inelastic decay of an ultracold, optically trapped fermionic ${}^{\mathrm{6}}\mathrm{L}\mathrm{i}$ gas of different spin compositions. The spin mixture of the two lowest hyperfine states showed two decay resonances at 550 and 680 G, consistent with the predicted Feshbach resonances for elastic $s$-wave collisions. The observed lifetimes of several hundred ms are much longer than the expected time for Cooper pair formation and the phase transition to superfluidity in the vicinity of the Feshbach resonance.