Theory of the Magnetic-Field-Induced Insulator in Neutral Graphene

TL;DR

This paper uses a theoretical model to analyze how magnetic fields induce insulating states in neutral graphene, identifying likely ground states and their properties.

Contribution

It introduces a Hartree-Fock calculation to compare candidate insulating states, highlighting the conditions favoring spin-density-wave or charge-density-wave ground states.

Findings

Spin-density-wave is likely in substrate-supported graphene.

Charge-density-wave may occur in suspended graphene.

Neither state supports gapless edge excitations.

Abstract

Recent experiments have demonstrated that neutral graphene sheets have an insulating ground state in the presence of an external magnetic field. We report on a $\pi$-band tight-binding-model Hartree-Fock calculation which examines the competition between distinct candidate insulating ground states. We conclude that for graphene sheets on substrates the ground state is most likely a field-induced spin-density-wave, and that a charge density wave state is possible for suspended samples. Neither of these density-wave states support gapless edge excitations.