Type-II Dirac surface states in topological crystalline insulators

TL;DR

This paper investigates topological crystalline insulators, revealing the coexistence of type-I and type-II Dirac surface states with distinct Fermi surface geometries and characteristic van-Hove singularities, using ab-initio calculations.

Contribution

It demonstrates the presence of both type-I and type-II Dirac surface states in topological crystalline insulators, highlighting their protected nature and unique electronic features.

Findings

Type-II Dirac states have open electron and hole pockets.

Type-II states show van-Hove singularities in dispersion.

Surface states respond distinctly to magnetic fields.

Abstract

We study the properties of a family of anti-pervoskite materials, which are topological crystalline insulators with an insulating bulk but a conducting surface. Using ab-initio DFT calculations, we investigate the bulk and surface topology and show that these materials exhibit type-I as well as type-II Dirac surface states protected by reflection symmetry. While type-I Dirac states give rise to closed circular Fermi surfaces, type-II Dirac surface states are characterized by open electron and hole pockets that touch each other. We find that the type-II Dirac states exhibit characteristic van-Hove singularities in their dispersion, which can serve as an experimental fingerprint. In addition, we study the response of the surface states to magnetic fields.