Electronic properties of asymmetrically doped twisted graphene bilayers

TL;DR

This paper investigates how asymmetric doping affects the electronic properties of twisted graphene bilayers across various rotation angles, revealing that doping can mimic the effects of changing the twist angle on electronic behavior.

Contribution

It provides a detailed analysis of the impact of asymmetric doping on the electronic structure of twisted bilayer graphene using tight binding calculations, highlighting doping as a tool to tune electronic properties.

Findings

Small doping preserves angle-dependent electronic features.

Large doping further reduces band velocity similar to decreasing twist angle.

Doping influences localization and density of states in twisted bilayers.

Abstract

Rotated graphene bilayers form an exotic class of nanomaterials with fascinating electronic properties governed by the rotation angle theta. For large rotation angles, the electron eigenstates are restricted to one layer and the bilayer behaves like two decoupled graphene layer. At intermediate angles, Dirac cones are preserved but with a lower velocity and van Hove singularities are induced at energies where the two Dirac cones intersect. At very small angles, eigenstates become localized in peculiar moire zones. We analyse here the effect of an asymmetric doping for a series of commensurate rotated bilayers on the basis of tight binding calculations of their band dispersions, density of states, participation ratio and diffusive properties. While a small doping level preserves the theta dependence of the rotated bilayer electronic structure, larger doping induces a further reduction of the band velocity in the same way of to a further reduction of the rotation angle.