Infrared absorption of closely-aligned heterostructures of monolayer and bilayer graphene with hexagonal boron nitride

TL;DR

This paper models the optical absorption of closely-aligned monolayer and bilayer graphene on hexagonal boron nitride, highlighting how spectral features can reveal moire pattern characteristics and the effects of doping and electric fields.

Contribution

It provides a theoretical analysis of how optical absorption spectra depend on moire superlattice parameters and external conditions, aiding interpretation of experimental data.

Findings

Absorption spectra can be similar despite different symmetry perturbations.

Doping dependence of absorption spectra can reveal moire characteristics.

Opposite electric-field-induced asymmetries in bilayer graphene offer additional insights.

Abstract

We model optical absorption of monolayer and bilayer graphene on hexagonal boron nitride for the case of closely-aligned crystal lattices. We show that perturbations with different spatial symmetry can lead to similar absorption spectra. We suggest that a study of the absorption spectra as a function of the doping for almost completely full first miniband is necessary to extract meaningful information about the moire characteristics from optical absorption measurements and to distinguish between various theoretical proposals for the physically realistic interaction. Also, for bilayer graphene, the ability to compare spectra for the opposite signs of electric-field-induced interlayer asymmetry might provide additional information about the moire parameters.