Signature of band inversion in the antiferromagnetic phase of axion insulator candidate EuIn_{2}As_{2}

We have performed angle-resolved photoemission spectroscopy on EuIn_{2}As_{2} 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 Γ point of the 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 an “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 Γ point in the antiferromagnetic phase. We suggest that EuIn_{2}As_{2} provides a good opportunity to study the exotic quantum phases associated with a possible axion-insulator phase.