Dynamic formation of quasicondensate and spontaneous vortices in a strongly interacting Fermi gas

Abstract

We report an experimental study of quench dynamics across the superfluid transition temperature T_{c} in a strongly interacting Fermi gas by ramping down the trapping potential. The nonzero quasicondensate number N_{0} at temperatures significantly above T_{c} in the unitary and the BEC regimes is consistent with the pseudogap physics via preformed pairs. Below T_{c}, a rapid growth of N_{0} is accompanied by the spontaneous generation of tens of vortices. We observe a power-law scaling of the vortex density versus the quasicondensate formation time, consistent with the Kibble-Zurek theory. Our work provides an example of studying emerged many-body physics by quench dynamics and paves the way for studying the quantum turbulence in a strongly interacting Fermi gas.