Supercritical superfluid and vortex unbinding following a quantum quench

We study the dynamics of the relative phase of a bilayer of two-dimensional superfluids after the two superfluids have been decoupled, using truncated Wigner approximation. On short time scales the relative phase shows light-cone-like thermalization and creates a metastable superfluid state, which can be supercritical. On longer time scales this state relaxes to a disordered state due to dynamical vortex unbinding. This scenario of dynamically suppressed vortex proliferation constitutes a reverse-Kibble-Zurek effect. We observe dynamics of creation of vortex-antivortex pairs and their consequent motion. Our predictions can be directly measured in interference experiments [Z. Hadzibabic , Nature (London) 441, 1118 (2006)].