Optical absorption of twisted bilayer graphene with interlayer potential asymmetry

TL;DR

This paper studies how interlayer bias and Fermi energy affect the band structure and optical absorption in twisted bilayer graphene, revealing tunable spectral features sensitive to external fields.

Contribution

It provides a detailed analysis of the effects of interlayer potential asymmetry on the electronic and optical properties of twisted bilayer graphene, highlighting tunability.

Findings

Interlayer bias lifts the degeneracy of the superlattice Dirac point.

The Dirac point shift is suppressed at small rotation angles.

Optical absorption spectra are highly sensitive and tunable by external fields.

Abstract

We investigate the band structure and the optical absorption spectrum of twisted bilayer graphenes with changing interlayer bias and Fermi energy simultaneously. We show that the interlayer bias lifts the degeneracy of the superlattice Dirac point, while the amount of the Dirac point shift is significantly suppressed in small rotation angles, and even becomes opposite to the applied bias. We calculate the optical absorption spectrum in various asymmetric potentials and Fermi energies, and associate the characteristic spectral features with the band structure. The spectroscopic features are highly sensitive to the interlayer bias and the Fermi energy, and widely tunable by the external field effect.