Dynamical instability in kicked Bose-Einstein condensates: Bogoliubov resonances

TL;DR

This paper demonstrates that dynamical instability in kicked Bose-Einstein condensates arises from resonant excitation of Bogoliubov modes rather than chaos, supported by an analytical model and numerical simulations.

Contribution

It identifies Bogoliubov resonances as the cause of instability and provides an analytical model that explains the scaling of these resonances in kicked BECs.

Findings

Instability is driven by resonant Bogoliubov mode excitation.

Analytical model accurately predicts resonance scaling.

Good agreement between theory and mean-field numerics.

Abstract

Bose-Einstein condensates subject to short pulses (`kicks') from standing waves of light represent a nonlinear analogue of the well-known chaos paradigm, the quantum kicked rotor. Previous studies of the onset of dynamical instability (ie exponential proliferation of non-condensate particles) suggested that the transition to instability might be associated with a transition to chaos. Here we conclude instead that instability is due to resonant driving of Bogoliubov modes. We investigate the excitation of Bogoliubov modes for both the quantum kicked rotor (QKR) and a variant, the double kicked rotor (QKR-2). We present an analytical model, valid in the limit of weak impulses which correctly gives the scaling properties of the resonances and yields good agreement with mean-field numerics.