Band Symmetries and Singularities in Twisted Multilayer Graphene

TL;DR

This paper investigates the electronic spectra of twisted multilayer graphene, revealing two distinct states with unique symmetry and singularity features, and compares theoretical predictions with experimental observations.

Contribution

It introduces a continuum model that identifies two different electronic states in twisted bilayer graphene, highlighting their unique symmetry and spectral properties.

Findings

One state shows Fermi velocity reduction and Dirac node annihilation.

The other state exhibits symmetry-protected Dirac singularities.

Results align with experimental data and previous theories.

Abstract

The electronic spectra of rotationally faulted graphene bilayers are calculated using a continuum formulation for small fault angles that identifies two distinct electronic states of the coupled system. The low energy spectra of one state features a Fermi velocity reduction which ultimately leads to pairwise annihilation and regeneration of its low energy Dirac nodes. The physics in the complementary state is controlled by pseudospin selection rules that prevent a Fermi velocity renormalization and produce second generation symmetry-protected Dirac singularities in the spectrum. These results are compared with previous theoretical analyses and with experimental data.