Topological character of the antiferromagnetic EuMg$_{2}$Bi$_{2}$

Abstract

Antiferromagnetic EuM$_{2}$Pn$_{2}$ compounds, where M is a metal element and Pn is a pnictogen element, have been recognized as candidates for realizing a topologically nontrivial electronic structure. In this paper, we focus on EuMg$_2$Bi$_2$, whose topological nature still remains unclear. We present a comprehensive study based on several experimental and theoretical techniques. Magnetic susceptibility, electrical resistivity, and specific heat capacity measurements confirm the existence of an antiferromagnetic ordering. The electronic band structure was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES), supported by ab initio calculations. ARPES measurement reveals that the electronic structure of this system is dominated by linearly dispersive hole-like bands near the Fermi level. Theoretical analyses of the electronic band structure indicates that EuMg$_2$Bi$_2$ is a strong topological insulator, which should be reflected in the presence of a metallic surface state. We also theoretically examine the magnetic-field-induced anomalous Hall conductivity, confirming previously reported observations.