Floquet boundary states in AB-stacked graphite

TL;DR

This paper demonstrates that circularly polarized laser light induces topological boundary states in AB-stacked graphite, potentially enabling a 3D quantum Hall effect in Floquet systems.

Contribution

It reveals the emergence of topological Floquet boundary states in graphite under circularly polarized light, extending 2D topological phenomena to 3D layered materials.

Findings

Laser illumination opens band gaps at Floquet zone edges.

Chiral boundary states propagate along layer borders.

States exhibit topological characteristics similar to 2D systems.

Abstract

We report on the effect of laser illumination with circularly polarized light on the electronic structure of AB-stacked graphite samples. By using Floquet theory in combination with Green's function techniques, we find that the polarized light induces band-gap openings at the Floquet zone edge $\hbar\Omega/2$, bridged by chiral boundary states. These states propagate mainly along the borders of the constituting layers as evidenced by the time-averaged local density of states and the probability current density in several geometries. Semianalytic calculations of the Chern number suggest that these states are of topological nature, similar to those found in illuminated 2D samples like monolayer and bilayer graphene. These states are promising candidates for the realization of a three-dimensional version of the quantum Hall effect for Floquet systems.