Chiral Symmetry and Electron-Electron Interaction in Many-Body Gap Formation in Graphene

TL;DR

This paper investigates how chiral symmetry and electron-electron interactions influence the many-body ground state and edge phenomena in graphene under magnetic fields, revealing a degenerate chiral condensate and edge charge accumulation.

Contribution

It demonstrates that chiral symmetry determines a doubly degenerate ground state and elucidates the nature of edge modes and gap formation in graphene.

Findings

Ground state is a doubly degenerate chiral condensate at half-filling.

Charge accumulates along zigzag edges in the ground state.

Gapless excitations are absent despite edge modes.

Abstract

We study a many-body ground state of graphene in perpendicular magnetic fields. Chiral symmetry in graphene enables us to determine the many-body ground state, which turns out to be a doubly degenerate chiral condensate for the half-filled (undoped) case. In the ground state a prominent charge accumulation emerges along zigzag edges. We also show that gapless excitations are absent despite the presence of the robust edge modes, which is consistent with the Chern number C = 0.