Theoretical study of optical conductivity of graphene with magnetic and nonmagnetic adatoms

TL;DR

This paper provides a theoretical analysis of how magnetic and nonmagnetic adatoms affect the optical conductivity of graphene, revealing gap formation mechanisms and proposing methods to interpret adatom magnetic states from optical data.

Contribution

It introduces a theoretical framework for understanding gap formation in graphene due to adatoms and offers a novel way to infer adatom magnetic properties from optical conductivity measurements.

Findings

Antiferromagnetic adatom configuration opens a gap in graphene.

Optical conductivity can distinguish between different adatom-induced gap mechanisms.

Application to oxygenated graphene data supports the theoretical approach.

Abstract

We present a theoretical study of the optical conductivity of graphene with magnetic and nonmagnetic adatoms. First, by introducing alternating potential in a pure graphene, we demonstrate a gap formation in the density of states and the corresponding optical conductivity. We highlight the distinction between such a gap formation and the so-called Pauli blocking effect. Next, we apply this idea to graphene with adatoms by introducing magnetic interactions between the carrier spins and the spins of the adatoms. Exploring various possible ground-state spin configurations of the adatoms, we find that antiferromagnetic configuration yields the lowest total electronic energy, and is the only configuration that forms a gap. Furthermore, we analyze four different circumstances leading to similar gaplike structures and propose a means to interpret the magneticity and the possible orderings of the adatoms on graphene solely from the optical conductivity data. We apply this analysis to the recently reported experimental data of oxygenated graphene.