Dissipative Floquet Topological Systems

TL;DR

This paper investigates how phonon dissipation influences the nonequilibrium electron distribution in Floquet topological systems, revealing a transition from anisotropic to isotropic distributions with potential implications for quantized transport.

Contribution

It introduces a Floquet kinetic equation approach to analyze phonon effects on Dirac fermions under laser irradiation, highlighting the emergence of a unique nonequilibrium distribution.

Findings

Phonons smooth out initial anisotropic distributions.

The resulting distribution is isotropic and distinct from thermal states.

An analytical expression at the Dirac point predicts quantized transport.

Abstract

Motivated by recent pump-probe spectroscopies, we study the effect of phonon dissipation and potential cooling on the nonequilibrium distribution function in a Floquet topological state. To this end, we apply a Floquet kinetic equation approach to study two dimensional Dirac fermions irradiated by a circularly polarized laser, a system which is predicted to be in a laser induced quantum Hall state. We find that the initial electron distribution shows an anisotropy with momentum dependent spin textures whose properties are controlled by the switching-on protocol of the laser. The phonons then smoothen this out leading to a non-trivial isotropic nonequilibrium distribution which has no memory of the initial state and initial switch-on protocol, and yet is distinct from a thermal state. An analytical expression for the distribution at the Dirac point is obtained that is relevant for observing quantized transport.