Gate-tunable bandgap in bilayer graphene

TL;DR

This paper models how the electronic bandgap in bilayer graphene can be tuned by gate voltage and doping, providing a theoretical framework that matches experimental observations.

Contribution

It introduces a theoretical model for the gate-tunable bandgap in bilayer graphene considering doping effects and screening, aligning well with experimental data.

Findings

The bandgap is proportional to gate voltage in undoped samples.

Doping causes asymmetrical behavior of the bandgap on electron and hole sides.

The model agrees with experimental measurements by Kuzmenko et al.

Abstract

The tight-binding model of bilayer graphene is used to find the gap between the conduction and valence bands, as a function of both the gate voltage and as the doping by donors or acceptors. The total Hartree energy is minimized and the equation for the gap is obtained. This equation for the ratio of the gap to the chemical potential is determined only by the screening constant. Thus the gap is strictly proportional to the gate voltage or the carrier concentration in the absence of donors or acceptors. In the opposite case, where the donors or acceptors are present, the gap demonstrates the asymmetrical behavior on the electron and hole sides of the gate bias. A comparison with experimental data obtained by Kuzmenko et al demonstrates the good agreement.