Floquet Chern Insulators and Radiation-Induced Zero Resistance in Irradiated Graphene

TL;DR

This paper predicts that irradiated graphene under circularly polarized light can exhibit novel nonequilibrium states with zero resistance, including Floquet Chern insulators at high frequencies and a radiation-induced zero-resistance state at low frequencies, with detailed phase diagrams.

Contribution

It introduces the concept of Floquet Chern insulators and radiation-induced zero-resistance states in irradiated graphene, providing theoretical phase diagrams and conductivities.

Findings

Floquet Chern insulators occur at high driving frequencies.

Negative resistance and irregular conductivities appear at low frequencies.

Spontaneous inhomogeneous current distributions form in the zero-resistance state.

Abstract

Recent advances in optics and time-resolved techniques have facilitated the exploration of new states of matter under nonequilibrium conditions. Here, we predict that irradiated graphene can host two novel nonequilibrium steady states of matter with zero resistance when exposed to circularly polarized light: (i) Floquet Chern insulators and (ii) a radiation-induced zero-resistance state with spontaneous formation of an inhomogeneous current distribution. Specifically, we calculate nonequilibrium anomalous Hall and longitudinal conductivities to map the nonequilibrium phase diagram of irradiated graphene as a function of the driving frequency and the electric-field strength of circularly polarized light. As a result, Floquet Chern insulators are found to occur at high driving frequencies above the graphene band width. By contrast, at low driving frequencies below the graphene band width, the nonequilibrium anomalous Hall conductivity deviates from the expected quantized values, and the nonequilibrium longitudinal conductivity exhibits highly irregular behavior, including negative resistance. It is predicted that the thermodynamically unstable negative resistance will trigger a catastrophic breakdown, inducing a zero-resistance state with spontaneous formation of an inhomogeneous current distribution, similar to the radiation-induced zero-resistance state observed in quantum Hall systems.