Electronic properties of bilayer graphenes strongly coupled to interlayer stacking and an external electric field

TL;DR

This study uses density functional theory to analyze how stacking variations and external electric fields affect the electronic properties of bilayer graphene, revealing stacking-dependent bandgap behavior and persistent midgap states.

Contribution

First comprehensive phase diagram of stacking-dependent bandgap openings in bilayer graphene under electric fields, highlighting the impact of grain boundary states on transport properties.

Findings

Stacking influences bandgap opening in bilayer graphene.

Midgap states localized on grain boundaries persist under strong fields.

Transport gap can be reduced by midgap states despite external electric fields.

Abstract

Bilayer graphene (BLG) with a tunable bandgap appears interesting as an alternative to graphene for practical applications, thus its transport properties are being actively pursued. Using density functional theory and perturbation analysis, we investigated, under an external electric field, the electronic properties of BLGs in various stackings relevant to recently observed complex structures. We established the first phase diagram summarizing the stacking-dependent gap openings of BLGs for a given field. We further identified high-density midgap states, localized on grain boundaries, even under a strong field, which can considerably reduce overall transport gap.