Quasi-Equilibrium Distributions for Periodically Driven Quantum Systems
Periodically driven quantum systems play a particularly important role in the study of non-equilibrium dynamics: On the one hand, they are continually forced out of thermal equilibrium through the action of a time-periodic external stimulus; on the other, they are still characterized by constant occupation probabilities of their Floquet states. This project addresses the determination and deliberate manipulation of such Floquet-state occupation distributions, both for single-particle and many-body systems. In a first step, we will consider strongly driven, but isolated anharmonic oscillators, investigating the possibility of prethermalization to a long-lived quasistationary state. We will also study driven oscillators in contact with an environment, determine the resulting quasi-equilibrium Floquet-state occupation distributions, and explore to what extent such distributions can be tailored by suitable design of the system-bath coupling. Particular emphasis will be given to the population of resonance-induced effective ground states, and to the generation of stable subharmonic dynamics. In a further step we will consider anharmonically trapped, periodically driven quantum gases, and identify those Floquet-state distributions which replace the Bose- and Fermi distributions in such systems. Here, one of the most interesting questions concerns the possible existence of metastable Floquet condensates.