Optotwistronic of bilayer graphene

TL;DR

This paper investigates the nonlinear optical properties of twisted bilayer graphene, emphasizing the role of Berry phase and the emergence of harmonic generation at moderate field strengths due to reduced band width.

Contribution

It reveals how Berry phase influences nonlinearity and demonstrates harmonic generation in twisted bilayer graphene under moderate fields, advancing understanding of geometry-related optical effects.

Findings

Berry phase contributes to nonlinearity when inversion symmetry is broken

Harmonic generation occurs at moderate field strengths

Reduced band width facilitates extreme nonlinear optical effects

Abstract

We present a study of the nonlinear optical response of twisted bilayer graphene. We discuss the contribution of the Berry phase to the non-linearity when inversion symmetry is broken, thus underlining the interplay between band and real space geometry, and nonlinear response. We also highlight an effect which is characteristic of extreme nonlinear optics: the generation of harmonics in disguise. This effect emerges in twisted bilayer graphene at relatively moderate fields strengths because of the much reduced band width. Our findings contribute to the understanding of the link between geometry and optical properties, as well as of the extreme nonlinear optical regime in twisted bilayer graphene