Equilibrating dynamics in quenched Bose gases: Characterizing multiple time regimes

We address the physics of equilibration in ultracold atomic gases following a quench of the interaction parameter. Our work is based on a bath model which generates damping of the bosonic excitations. We illustrate this dissipative behavior through the momentum distribution of the excitations nₖ, observing that larger k modes have shorter relaxation times τ(k); they will equilibrate faster, as has been claimed in recent experimental work. We identify three time regimes. At short times nₖ exhibits oscillations; these are damped out at intermediate times where the system appears to be in a false or slowly converging equilibrium. Finally, at longer times, full equilibration occurs. This false equilibrium is, importantly, associated with the k dependence in τ(k) and has implications for experiment.