Prethermalization to thermalization crossover in a dilute Bose gas following an interaction ramp

TL;DR

This paper investigates the transition from prethermalization to thermalization in a dilute Bose gas after an interaction ramp, highlighting the role of quasiparticle interactions and their experimental observability.

Contribution

It elucidates the crossover dynamics from prethermal to thermal states in a weakly interacting Bose gas, emphasizing the impact of higher-order quasiparticle interactions.

Findings

Prethermalization occurs rapidly after the interaction ramp.

Long-term thermalization is driven by quasiparticle collisions.

The crossover dynamics are accessible in current ultracold atom experiments.

Abstract

The dynamics of a weakly interacting Bose gas at low temperatures is close to integrable due to the approximate quadratic nature of the many-body Hamiltonian. While the short-time physics after an abrupt ramp of the interaction constant is dominated by the integrable dynamics, integrability is broken at longer times by higher-order interaction terms in the Bogoliubov Hamiltonian, in particular by Beliaev-Landau scatterings involving three quasiparticles. The two-stage relaxation process is highlighted in the evolution of local observables such as the density-density correlation function: a dephasing mechanism leads the system to a prethermal stage, followed by true thermalization conveyed by quasiparticle collisions. Our results bring the crossover from prethermalization to thermalization within reach of current experiments with ultracold atomic gases.