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arXiv · 2209.09972

Surface state evolution induced by magnetic order in axion insulator candidate EuIn2As2

Mingda Gong·Divyanshi Sar·Joel Friedman·Dariusz Kaczorowski·S. Abdel Razek·Wei-Cheng Lee·Pegor Aynajian
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Abstract

Gapping of Dirac surface states through time reversal symmetry breaking may realize the axion insulator state in condensed matter. Despite tremendous efforts, only a few material systems fall in this category of intrinsic magnetic topological insulators (TI). Recent theoretical calculations proposed the antiferromagnetic EuIn$_2$As$_2$ to be a topologically non-trivial magnetic insulator with gapped surface states. Here we use scanning tunneling microscopy and spectroscopy (STM/STS) complemented with density-functional theory (DFT) calculations and modelling to probe the surface electronic states in EuIn$_2$As$_2$. We find a spin-orbit induced bulk gap of ~120 meV located only a few meV above the Fermi energy, within which topological surface states reside. Temperature dependent measurements provide evidence of the partial gapping (~40 meV) of the surface states at low temperatures below the AFM order, which decreases with increasing temperature but remains finite above $T_N$

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Mingda Gong, Divyanshi Sar, Joel Friedman, Dariusz Kaczorowski, S. Abdel Razek, Wei-Cheng Lee, Pegor Aynajian. 2022-09-20. Surface state evolution induced by magnetic order in axion insulator candidate EuIn2As2. https://doi.org/10.1103/physrevb.106.125156

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