The Dynamical Condensation Phase Transition
Nicolas Cherroret (LKB, Paris)
Following a quantum quench, local observables in non-integrable many-body systems typically thermalize. In certain cases, however, this process can be critically slowed down: the system first exhibits universal dynamical scaling laws with strongly non-thermal properties, before eventually reaching thermal equilibrium on a longer time scale. This behavior has been referred to as a non-thermal fixed point. In this talk, I will discuss the far-from-equilibrium dynamics of 3D Bose gases suddenly quenched across their condensation transition. I will show that this dynamics gives rise to distinct (non)-thermal fixed points, depending on whether the quench is performed above, at or below the critical point. In particular, quenches below the critical point generally involve a transient regime of weak turbulence, followed at later times by a coarsening dynamics associated with the slow recombination of vortex lines. Quenches at the critical point, on the other hand, lead to a universal dynamics presumably without vortices but involving the diffusion of critical fluctuations. If time permits, I will also discuss how this universal dynamics is destabilized in the presence of perturbations, specifically external drive and disorder.