Nonequilibrium quench dynamics of Bose-Einstein condensates of microwave-shielded polar molecules

TL;DR

This paper models the non-equilibrium dynamics of microwave-shielded polar molecule Bose gases after a sudden interaction change, revealing oscillatory behaviors and steady-state properties distinct from equilibrium.

Contribution

It introduces a theoretical framework combining Bogoliubov and Hartree-Fock-Bogoliubov methods to analyze quenched polar molecule condensates, highlighting their non-equilibrium steady states.

Findings

Quantum depletion and correlations oscillate depending on shielding strength.

Long-time steady states show deviations from equilibrium distributions.

Pair correlations transition from diffusive to ballistic spreading over time.

Abstract

We theoretically investigate the non-equilibrium dynamics of homogeneous ultracold Bose gases of microwave-shielded polar molecules following a sudden quench of the scattering length at zero temperature. We calculate in particular the quantum depletion, the anomalous density, the condensate fluctuations, and the pair correlation function using both the time-dependent Bogoliubov approach and the self-consistent time-dependent Hartree-Fock-Bogoliubov approximation. During their time evolution, these quantities exhibit slow or fast oscillations depending on the strength of the shielding interactions. We find that at long time scales the molecular condensate is characterized by nonequilibrium steady-state momentum distribution functions, with depletion, anomalous density and correlations that deviate from their corresponding equilibrium values. We demonstrate that the pair correlations expand diffusively at short times while they spread ballistically at long times.