Controlled Population of Floquet-Bloch States via Coupling to Bose and Fermi Baths

TL;DR

This paper investigates how to control the steady states of a driven quantum system by coupling it to phonon and fermionic reservoirs, proposing methods to realize Floquet topological insulators with insulating behavior and specific transport properties.

Contribution

It introduces a kinetic framework for controlling Floquet-Bloch states via reservoir coupling and energy filtering, advancing the design of non-equilibrium quantum phases.

Findings

Steady states can be tuned using phonon and Fermi reservoir couplings.

Coupling via an energy filter suppresses photon-assisted tunneling.

The system can exhibit insulating behavior with a small density of excitations.

Abstract

External driving is emerging as a promising tool for exploring new phases in quantum systems. The intrinsically non-equilibrium states that result, however, are challenging to describe and control. We study the steady states of a periodically driven one-dimensional electronic system, including the effects of radiative recombination, electron-phonon interactions, and the coupling to an external fermionic reservoir. Using a kinetic equation for the populations of the Floquet eigenstates, we show that the steady-state distribution can be controlled using the momentum and energy relaxation pathways provided by the coupling to phonon and Fermi reservoirs. In order to utilize the latter, we propose to couple the system and reservoir via an energy filter which suppresses photon-assisted tunneling. Importantly, coupling to these reservoirs yields a steady state resembling a band insulator in the Floquet basis. The system exhibits incompressible behavior, while hosting a small density of excitations. We discuss transport signatures, and describe the regimes where insulating behavior is obtained. Our results give promise for realizing Floquet topological insulators.