Nicolas Cherroret is visiting us

Nicolas Cherroret from Laboratoire Kastler Brossel in Paris is visiting us to talk about his most recent results on out-of-equilibrium physics with atomic and optical fluids.

Understanding how a many-body system evolves dynamically and possibly returns to a thermal equilibrium state after a perturbation (or 'quench') is a fundamental challenge in quantum, classical and statistical physics. In this context, weakly interacting quantum fluids are particularly interesting, because their post-quench dynamics usually involves a long-lived stage ('prethermalization'), during which peculiar coherence properties and interference phenomena emerge, before the system eventually thermalizes.

After a general introduction, I will first discuss in more detail the non-equilibrium dynamics of 2D Bose superfluids, which have been recently investigated in several experiments involving cold atoms and fluids of light. I will also present our theoretical description of these systems, which allows us to capture their full dynamics, from the initial quench to the final thermalization occurring at long times. In a second part, I will say a few words on ongoing theoretical and experimental works on the dynamics of superfluid mixtures, which have the peculiarity of displaying a miscible-immiscible phase transition. When perturbed in the miscible phase, superfluid mixtures also evolve into a prethermal stage, during which interesting 'spin' and 'density' waves can be observed. When perturbed in the immiscible phase, in contrast, they exhibit a highly nonlinear dynamics, characterized by domains formation and spatio-temporal scaling laws, without any evolution toward thermalization.