Electron Interactions and Gap Opening in Graphene Superlattices

TL;DR

This paper presents a theory predicting that electron interactions in graphene superlattices can significantly enhance the Dirac point gap, explaining recent experimental observations and offering tunability via superlattice periodicity.

Contribution

The paper introduces a theoretical framework for interaction effects in graphene superlattices, highlighting the potential for large, tunable Dirac point gap enhancements.

Findings

Many-body interactions can substantially increase the Dirac gap.

Tunable superlattice periodicity allows control over the gap size.

Large gaps observed in experiments are explained by interaction effects.

Abstract

We develop a theory of interaction effects in graphene superlattices, where tunable superlattice periodicity can be used as a knob to control the gap at the Dirac point. Applied to graphene on hexa-boron-nitride (G/h-BN), our theory predicts substantial many-body enhancement of this gap. Tunable by the moire superlattice periodicity, a few orders of magnitude enhancement is reachable under optimal conditions. The Dirac point gap enhancement can be much larger than that of the minigaps opened by Bragg scattering at principal superlattice harmonics. This naturally explains the conundrum of large Dirac point gaps recently observed in G/h-BN heterostructures and their tunability by the G/h-BN twist angle.