Floquet-heating-induced Bose condensation in a scar-like mode of an open driven optical-lattice system

Abstract

Periodically driven quantum systems suffer from heating via resonant excitation. While such Floquet heating guides a generic isolated system towards the infinite temperature state, a driven open system, coupled to a thermal bath, will approach a non-equilibrium steady state, which is determined by the interplay of driving and dissipation. Here, we show that this interplay can give rise to the counterintuitive effect that Floquet heating can induce Bose condensation. We consider a one-dimensional Bose gas in an optical lattice of finite extent, which is coupled weakly to a threedimensional thermal bath given by a second atomic species. The bath temperature T lies well above the crossover temperature, below which the majority of the system's particles form a (finite-size) Bose condensate in the ground state. However, when a strong local potential modulation is switched on, which resonantly excites the system, a non-equilibrium Bose condensate is formed in a state that decouples from the drive. Our predictions, which are based on a microscopic model that is solved using kinetic equations of motion derived from Floquet-Born-Markov theory, can be probed under realistic experimental conditions.