Prethermal Floquet Steady States and Instabilities in the Periodically Driven, Weakly Interacting Bose-Hubbard Model

TL;DR

This paper investigates the nonequilibrium steady states and instabilities of a periodically driven weakly interacting Bose-Hubbard model, revealing how drive strength influences condensate stability and providing insights relevant to ultracold atom experiments.

Contribution

It develops a weak-coupling conserving approximation to describe the nonequilibrium dynamics at arbitrary drive parameters, identifying stability regimes for different condensates.

Findings

Increased drive strength enhances condensate stability.

Bandwidth reduction of quasiparticles impedes resonant heating.

Stable regimes for zero-momentum and $(\pi,\pi)$-momentum condensates are established.

Abstract

We explore prethermal Floquet steady states and instabilities of the weakly interacting two-dimensional Bose-Hubbard model subject to periodic driving. We develop a description of the nonequilibrium dynamics, at arbitrary drive strength and frequency, using a weak-coupling conserving approximation. We establish the regimes in which conventional (zero-momentum) and unconventional [$(\pi,\pi)$-momentum] condensates are stable on intermediate time scales. We find that condensate stability is \emph{enhanced} by increasing the drive strength, because this decreases the bandwidth of quasiparticle excitations and thus impedes resonant absorption and heating. Our results are directly relevant to a number of current experiments with ultracold bosons.