Gate-induced Gap in Bilayer Graphene Suppressed by Coulomb Repulsion

TL;DR

This study explores how Coulomb repulsion influences the electric-field-induced band gap in bilayer graphene, revealing a surprising suppression of the gap due to the competition between Coulomb interactions and external electric fields.

Contribution

It introduces a theoretical analysis of Coulomb repulsion effects on the band gap in gated bilayer graphene using the ionic two-layer Hubbard model and coherent potential approximation.

Findings

Coulomb repulsion U suppresses the electric-field-induced gap.

Competition between U and electric field E leads to gap suppression.

Results explain discrepancies in experimental measurements of the gap.

Abstract

We investigate the effect of on-site Coulomb repulsion $U$ on the band gap of the electrically gated bilayer graphene by employing coherent potential approximation in the paramagnetic state, based on an ionic two-layer Hubbard model. We find that, while either the on-site Coulomb repulsion $U$ or the external perpendicular electric field $E$ alone will favor a gapped state in the bilayer graphene, competition between them will surprisingly lead to a suppression of the gap amplitude. Our results can be applied to understand the discrepancies of gap size reported from optical and transport measurements, as well as the puzzling features observed in angular resolved photoemission spectroscopic study.