Existence and topological stability of Fermi points in multilayered graphene

TL;DR

This paper investigates the existence and stability of Fermi points in multilayer graphene, revealing how symmetries and stacking order influence their stability and electronic structure.

Contribution

It demonstrates that discrete symmetries stabilize Fermi points in various multilayer graphene configurations and shows how stacking order and layer parity affect their stability.

Findings

Fermi points are stabilized by spacetime inversion symmetry in multilayer graphene.

Fermi points become unstable in multilayers with an odd number of layers under Bernal stacking.

Electronic structure changes due to perturbations mixing Dirac points are analyzed.

Abstract

We study the existence and topological stability of Fermi points in a graphene layer and stacks with many layers. We show that the discrete symmetries (spacetime inversion) stabilize the Fermi points in monolayer, bilayer and multilayer graphene with orthorhombic stacking. The bands near $k=0$ and $\epsilon=0$ in multilayers with the Bernal stacking depend on the parity of the number of layers, and Fermi points are unstable when the number of layers is odd. The low energy changes in the electronic structure induced by commensurate perturbations which mix the two Dirac points are also investigated.