Heating and many-body resonances in a periodically driven two-band system

TL;DR

This paper investigates the dynamics of a strongly interacting two-band system under periodic driving, revealing stable regimes at high frequencies and thermalization at low frequencies, with a focus on many-body resonances affecting thermalization.

Contribution

It introduces a detailed analysis of stability and thermalization in a driven two-band system, highlighting the role of Floquet many-body resonances in nonthermalizing behavior.

Findings

Stable regime at high driving frequencies with approximate energy conservation.

System heats up to infinite temperature at slow driving frequencies.

Rare Floquet many-body resonances cause nonthermalization in the crossover regime.

Abstract

We study the dynamics and stability in a strongly interacting resonantly driven two-band model. Using exact numerical simulations, we find a stable regime at large driving frequencies where the time evolution is governed by a local Floquet Hamiltonian that is approximately conserved out to very long times. For slow driving, on the other hand, the system becomes unstable and heats up to infinite temperature. While thermalization is relatively fast in these two regimes (but to different "temperatures"), in the crossover between them we find slow nonthermalizing time evolution: temporal fluctuations become strong and temporal correlations long lived. Microscopically, we trace back the origin of this nonthermalizing time evolution to the properties of rare Floquet many-body resonances, whose proliferation at lower driving frequency removes the approximate energy conservation, and thus produces thermalization to infinite temperature.