Magneto-optical response of graphene: probing substrate interactions

TL;DR

This paper investigates the magneto-optical properties of graphene on different substrates, revealing substrate-induced band gaps and proposing magneto-optical methods to probe superlattice effects, including excitonic interactions.

Contribution

It introduces a tight-binding approach to compare magneto-optical responses of isolated and substrate-supported graphene, accounting for superlattice effects and excitonic interactions.

Findings

Substrate interactions induce band gaps away from the Dirac point.

Magneto-optical response reveals Landau-level like structures from substrate-induced gaps.

The approach explains observed Fermi velocity renormalizations.

Abstract

Magneto-optical transitions between Landau levels can provide precise spectroscopic information on the electronic structure and excitation spectra of graphene, enabling probes of substrate and many-body effects. We calculate the magneto-optical conductivity of large-size graphene flakes using a tight-binding approach. Our method allows us to directly compare the magneto-optical response of an isolated graphene flake with one aligned on hexagonal boron nitride giving rise to a periodic superlattice potential. The substrate interaction induces band gaps away from the Dirac point. In the presence of a perpendicular magnetic field Landau-level like structures emerge from these zero-field band gaps. The energy dependence of these satellite structures is, however, not easily accessible by conventional probes of the density of states by varying the back-gate voltage. Here we propose the magneto-optical probing of the superlattice perturbed spectrum. Our simulation includes magneto-excitonic effects in first-order perturbation theory. Our approach yields a quantitative explanation of recently observed Landau-level dependent renormalizations of the Fermi velocity.