Radiation effects on the electronic structure of bilayer graphene

TL;DR

This paper investigates how laser illumination affects the electronic structure of bilayer graphene, revealing laser-induced gaps, polarization-dependent topological phases, and the influence of trigonal warping, with implications for optoelectronic applications.

Contribution

It introduces a theoretical framework combining Floquet theory and Green's functions to analyze laser-induced electronic and topological changes in bilayer graphene.

Findings

Laser induces gaps at multiple energies depending on polarization.

Linearly polarized light makes bilayer graphene a trivial insulator.

Circular polarization induces non-trivial topological phases.

Abstract

We report on the effects of laser illumination on the electronic properties of bilayer graphene. By using Floquet theory combined with Green's functions we unveil the appeareance of laser-induced gaps not only at integer multiples of $\hbar \Omega /2$ but also at the Dirac point with features which are shown to depend strongly on the laser polarization. Trigonal warping corrections are shown to lead to important corrections for radiation in the THz range, reducing the size of the dynamical gaps. Furthermore, our analysis of the topological properties at low energies reveals that when irradiated with linearly polarized light, ideal bilayer graphene behaves as a trivial insulator, whereas circular polarization leads to a non-trivial insulator per valley.