Peierls-type Instability and Tunable Band Gap in Functionalized Graphene

TL;DR

This paper demonstrates that controlled adatom adsorption on graphene induces a Peierls-like instability, leading to sublattice ordering and a tunable band gap, which is robust against disorder and doping variations.

Contribution

It reveals a mechanism for creating a tunable and stable band gap in graphene through adatom-induced Peierls instability and sublattice ordering.

Findings

Adatoms order via a Peierls-instability-type mechanism.

Band gap opens due to sublattice symmetry breaking.

The band gap remains stable despite positional disorder.

Abstract

Functionalizing graphene was recently shown to have a dramatic effect on the electronic properties of this material. Here we investigate spatial ordering of adatoms driven by the RKKY-type interactions. In the ordered state, which arises via a Peierls-instability-type mechanism, the adatoms reside mainly on one of the two graphene sublattices. Bragg scattering of electron waves induced by sublattice symmetry breaking results in a band gap opening, whereby Dirac fermions acquire a finite mass. The band gap is found to be immune to the adatoms' positional disorder, with only an exponentially small number of localized states residing in the gap. The gapped state is stabilized in a wide range of electron doping. Our findings show that controlled adsorption of adatoms or molecules provides a route to engineering a tunable band gap in graphene.