Evolution of the electronic band structure of twisted bilayer graphene upon doping

TL;DR

This study investigates how doping affects the electronic band structure of twisted bilayer graphene, revealing that charge doping can tune van Hove singularities and modify optical properties, with implications for electronic applications.

Contribution

It demonstrates the doping-induced evolution of van Hove singularities in twisted bilayer graphene using Raman spectroscopy, showing controllable modifications of electronic and optical properties.

Findings

Raman G peak area varies with doping and twist angle.

Van Hove singularity energy separation decreases with doping.

Electronic properties of twisted bilayer graphene can be tuned via doping.

Abstract

The electronic band structure of twisted bilayer graphene develops van Hove singularities whose energy depends on the twist angle between the two layers. Using Raman spectroscopy, we monitor the evolution of the electronic band structure upon doping using the G peak area which is enhanced when the laser photon energy is resonant with the energy separation of the van Hove singularities. Upon charge doping, the Raman G peak area initially increases for twist angles larger than a critical angle and decreases for smaller angles. To explain this behavior with twist angle, the energy of separation of the van Hove singularities must decrease with increasing charge density demonstrating the ability to modify the electronic and optical properties of twisted bilayer graphene with doping.