Antiferromagnetic crystalline topological insulators

TL;DR

This paper introduces a spinless antiferromagnetic model that exhibits a topologically non-trivial phase with a protected surface Dirac cone, even without spin or spin-orbit coupling, expanding the understanding of topological insulators.

Contribution

It demonstrates a novel antiferromagnetic spinless topological insulator model where surface states are protected by combined symmetries, independent of spin-orbit interactions.

Findings

Existence of a topologically non-trivial phase with a surface Dirac cone in a spinless model

Surface Dirac cone protected by combined time reversal and translation symmetry

Surface states can exist without spin-orbit coupling in magnetic crystals.

Abstract

The gapless surface Dirac cone of time reversal invariant topological insulators is protected by time reversal symmetry due to the Kramers' theorem. Spin degree of freedom is usually required since Kramers' theorem only guarantees double degeneracy for spinful fermions, but not for spinless fermions. In this paper, we present an antiferromagnetic spinless model, which breaks time reversal symmetry. Similar to time reversal invariant topological insulators, this model possesses a topologically non-trivial phase with a single surface Dirac cone, which is protected by the combination of time reversal and translation operation. Our results show that in magnetic crystals, a single Dirac cone can exist on the surface even without any spin degree of freedom and spin-orbit coupling.