Spontaneous Strains and Gap in Graphene on Boron Nitride

TL;DR

This paper models how the interaction between graphene and hBN induces strains and a spectral gap in graphene, revealing significant effects when their lattices are aligned, including large effective magnetic fields.

Contribution

It provides an analytical model linking adhesion forces to strains and spectral gaps in graphene on hBN, emphasizing the role of lattice alignment.

Findings

Strains of about 2% induce effective magnetic fields over 100T.

The spectral gap is significantly affected by strains and scalar potentials.

Commensuration effects are negligible due to graphene's stiffness.

Abstract

The interaction between a graphene layer and a hexagonal Boron Nitride (hBN) substrate induces lateral displacements and strains in the graphene layer. The displacements lead to the appearance of commensurate regions and the existence of an average gap in the electronic spectrum of graphene. We present a simple, but realistic model, by which the displacements, strains and spectral gap can be derived analytically from the adhesion forces between hBN and graphene. When the lattice axes of graphene and the substrate are aligned, strains reach a value of order 2\%, leading to effective magnetic fields above 100T. The combination of strains and induced scalar potential gives a sizeable contribution to the electronic gap. Commensuration effects are negligible, due to the large stiffness of graphene.