Optical Conductivity of Twisted Bilayer Graphene Near the Magic Angle

TL;DR

This paper investigates how lattice relaxation influences the optical conductivity of twisted bilayer graphene near the magic angle, revealing spectral features linked to band structure and relaxation effects.

Contribution

It provides a theoretical analysis of the impact of lattice relaxation on the optical conductivity and band structure of TBG near the magic angle, highlighting spectroscopic signatures.

Findings

Optical conductivity peaks correlate with van Hove singularities.

Lattice relaxation causes significant shifts in optical peaks.

Spectroscopic features can identify twist angle and relaxation effects.

Abstract

We theoretically study the band structure and optical conductivity of twisted bilayer graphene (TBG) near the magic angle considering the effects of lattice relaxation. We show that the optical conductivity spectrum is characterized by a series of peaks associated with the van Hove singularities in the band structure, and the peak energies evolve systematically with the twist angle. Lattice relaxation effects in TBG modify its band structure, especially the flat bands, which lead to significant shifts of the peaks in optical conductivity. These results demonstrate that spectroscopic features in the optical conductivity can serve as fingerprints for exploring the band structure, band gap and lattice relaxation in magic angle TBG as well as identifying its rotation angle.