Topological Surface States in Paramagnetic and Antiferromagnetic Iron Pnictides

TL;DR

This paper investigates the topological electronic structures of iron pnictides, revealing the existence of surface states in both paramagnetic and antiferromagnetic phases, with implications for their topological properties.

Contribution

It demonstrates the presence of topologically protected surface states in iron pnictides across different magnetic phases using realistic five-orbital models.

Findings

Surface states exist even in the paramagnetic phase.

Surface bands survive but split in the antiferromagnetic phase.

Topological analysis explains the surface state behavior.

Abstract

The electronic structure of iron pnictides is topologically nontrivial, leading to the appearance of Dirac cones in the band structure for the antiferromagnetic phase. Motivated by the analogy with Dirac cones in graphene, we explore the possible existence of topologically protected surface states. Surprisingly, bands of surface states exist even in the paramagnetic state. A realistic five-orbital model predicts two such bands. In the antiferromagnetic phase, these surface bands survive but split. We obtain the bulk and surface dispersion from exact diagonalization of two- and five-orbital models in a strip geometry and discuss the results based on topology.