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 quasi-condensate number $N_0$ at temperature significantly above $T_c$ in the unitary and the BEC regimes reveals the pseudogap physics. Below $T_c$, a rapid growth of $N_0$ is accompanied by spontaneous generation of tens of vortices. We observe a power law scaling of the vortex density versus the quasi-condensate 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.
Highlights
In pursuit of correlated quantum physics in strongly interacting Fermi gases, great efforts have been devoted to studying equilibrium phases and transitions [1,2,3,4,5,6]
Our experiment directly demonstrates the interplay between the real-time dynamics of quasicondensate growth and spontaneous vortex formation
The good agreement between theoretical calculations and experimental data demonstrates that our data can be explained by the pseudogap physics, which leads to significant differences in the growth dynamics of the quasicondensate between the BEC and BCS regimes
Summary
In pursuit of correlated quantum physics in strongly interacting Fermi gases, great efforts have been devoted to studying equilibrium phases and transitions [1,2,3,4,5,6]. This has shed light on the understanding of high-Tc superconductivity [7,8,9] and the modeling of equation of states of dense neutron stars [10]. The quench dynamics offers a great opportunity for understanding the interplay among the formation of bosonic pairs, superfluid phase coherence, and spontaneous vortices. We report an experimental study of the real-time dynamics of superfluid growth and spontaneous vortex formation in a strongly interacting Fermi gas of 6Li atoms. By using tf as the quench time, which is less sensitive to the pseudogap physics, a power-law scaling of ρv vs tf is observed for normal quenches, and the extracted critical exponent agrees quantitatively with that predicted by the KZ theory
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