Gap Opening by Asymmetric Doping in Graphene Bilayers

TL;DR

This paper investigates how asymmetric doping, through various impurities, opens an energy gap in graphene bilayers and compares it to electric field effects, revealing different behaviors and sensitivities.

Contribution

It provides a comparative analysis of energy gap opening mechanisms in graphene bilayers due to asymmetric doping and external electric fields, highlighting differences in impurity effects.

Findings

Adsorbed potassium mimics electric field effects on gap opening.

Substitutional impurities lead to smaller gaps and are highly sensitive to disorder.

Doping effects vary significantly depending on impurity type and placement.

Abstract

We study the energy gap opening in the electronic spectrum of graphene bilayers caused by asym- metric doping. Both substitutional impurities (boron acceptors and nitrogen donors) and adsorbed potassium donors are considered. The gap evolution with dopant concentration is compared to the situation in which the asymmetry between the layers is induced by an external electric field. The effects of adsorbed potassium are similar to that of an electric field, but substitutional impurities behave quite differently, showing smaller band gaps and a large sensitivity to disorder and sublattice occupation.