Interaction-induced metallic state in graphene on hexagonal boron nitride

TL;DR

This paper reveals that onsite Coulomb repulsion in graphene on h-BN initially destroys localized states, leading to a metallic state, contrary to the usual expectation of Coulomb interactions promoting localization.

Contribution

It demonstrates that Coulomb repulsion can suppress localization in graphene/h-BN heterostructures, explaining experimental observations and suggesting ways to control electronic states.

Findings

Coulomb repulsion initially destroys localized states in graphene/h-BN.

Both gapless and gapped states can be explained with realistic Coulomb values.

Proposes methods to enhance the gapped state for electronics applications.

Abstract

The Coulomb interaction is widely known to enhance the effective mass of interacting particles and therefore tends to favor a localized state at commensurate filling. Here, we will show that, in contrast to this consensus, in a van der Waals heterostructure consisting of graphene and hexagon boron nitride (h-BN), the onsite Coulomb repulsion will at first destroy the localized state. This is due to the fact that the onsite Coulomb repulsion tends to suppress the asymmetry between neighboring carbons induced by h-BN substrate. We corroborate this surprising phenomenon by solving a tight-binding model with onsite Coulomb repulsion treated within coherent potential approximation, where hopping parameters are derived from density functional theory calculations based on the graphene/h-BN heterostructure. Our results indicate that both gapless and gapped states observed experimentally in graphene/h-BN heterostructures can be understood after a realistic value of the onsite Coulomb repulsion as well as different interlayer distances are taken into account. Finally, we propose ways to enhance the gapped state which is essential for potential application of graphene to next-generation electronics. Furthermore, we argue that band gap suppressed by many-body effect should happen in other van der Waals heterostructures.