INPHYNI seminar: Nicolas Cherroret (LKB)

The way isolated many-body quantum systems return to thermal equilibrium after a quench is a fundamental yet largely open question in statistical physics. In this context, near-integrable systems play a special role, as thermalization typically proceeds in two distinct stages: their short-time dynamics is governed by the coherent evolution of independent quasiparticles, defining a "prethermalization" regime, while their long-time relaxation to equilibrium is driven by quasiparticle interactions.
In this talk, I will discuss quantum thermalization in representative near-integrable system: a 2D dilute Bose superfluid undergoing an interaction quench. Using a quantum hydrodynamic framework combined with a kinetic approach, I will describe the system's evolution from its short-time prethermal regime to its long-time thermalization, illustrating the results with recent experiments on atomic and optical superfluids. By focusing on long timescales, I will finally demonstrate that thermal relaxation itself exhibits a nontrivial dynamics, with global equilibration over large distances occurring very slowly after the Landau relaxation of quasiparticles.