Effective Theory of Floquet Topological Transitions

TL;DR

This paper develops a theoretical framework for Floquet topological transitions, revealing how disorder can enhance bulk transport in irradiated graphene, contrasting with static topological insulators.

Contribution

It introduces an analytical and numerical study of topological transitions in Floquet systems, highlighting the role of disorder in transport properties.

Findings

Suppression of bulk conductivity at certain Floquet topological transitions.

Disorder significantly enhances bulk transport in the system.

Analytical conditions for transport suppression are derived.

Abstract

We develop a theory of topological transitions in a Floquet topological insulator, using graphene irradiated by circularly polarized light as a concrete realization. We demonstrate that a hallmark signature of such transitions in a static system, i.e. metallic bulk transport with conductivity of order $e^2/h$, is substantially suppressed at some Floquet topological transitions in the clean system. We determine the conditions for this suppression analytically and confirm our results in numerical simulations. Remarkably, introducing disorder dramatically enhances this transport by several orders of magnitude.