Bound-state signatures in quenched Bose-Einstein condensates

TL;DR

This paper studies the non-equilibrium dynamics of a homogenous Bose-Einstein condensate after a sudden change in interaction strength, revealing bound-state effects through analytic models and oscillatory behavior in correlations.

Contribution

It introduces exactly solvable two-body models that accurately describe the short-time, short-range dynamics of quenched BECs, emphasizing the role of bound states.

Findings

Contact oscillates at the bound state frequency after quench

Oscillations in condensate fraction are significant

Bound states dominate short-time correlation dynamics

Abstract

We investigate the dynamics of a homogenous Bose-Einstein condensate (BEC) following a sudden quench of the scattering length. Our focus is the time evolution of short-range correlations via the dynamical contact. We compute the dynamics using a combination of two- and many-body models, and we propose an intuitive connection between them that unifies their short-time, short-range predictions. Our two-body models are exactly solvable and, when properly calibrated, lead to analytic formulae for the contact dynamics. Immediately after the quench, the contact exhibits strong oscillations at the frequency of the two-body bound state. These oscillations are large in amplitude, and their time average is typically much larger than the unregularized Bogoliubov prediction. The condensate fraction shows similar oscillations, whose amplitude we are able to estimate. These results demonstrate the importance of including the bound state in descriptions of diabatically-quenched BEC experiments.