Signature of band inversion in the antiferromagnetic phase of axion insulator candidate EuIn2As2

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate EuIn2As2, revealing band inversion in its antiferromagnetic phase, supporting its potential as an axion insulator and offering insights into exotic quantum phases.

Contribution

First experimental observation of band inversion in EuIn2As2's antiferromagnetic phase, aligning with theoretical predictions for axion insulators.

Findings

Identification of a bulk hole pocket at Gamma point

Observation of a band reconstruction with an 'M'-shaped bulk band

Qualitative agreement with first-principles calculations

Abstract

We have performed angle-resolved photoemission spectroscopy on EuIn2As2 which is predicted to be an axion insulator in the antiferromagnetic state. By utilizing soft-x-ray and vacuum-ultraviolet photons, we revealed a three-dimensional hole pocket centered at the Gamma point of bulk Brillouin zone together with a heavily hole-doped surface state in the paramagnetic phase. Upon entering the antiferromagnetic phase, the band structure exhibits a marked reconstruction characterized by the emergence of a "M"-shaped bulk band near the Fermi level. The qualitative agreement with first-principles band-structure calculations suggests the occurrence of bulk-band inversion at the Gamma point in the antiferromagnetic phase. We suggest that EuIn2As2 provides a good opportunity to study the exotic quantum phases associated with possible axion-insulator phase.