Metallic surface states in a correlated d-electron topological Kondo insulator candidate FeSb2

Ke-Jun Xu, Su-Di Chen, Yu He, Junfeng He, Shujie Tang, Chunjing Jia, Eric Yue Ma, Sung-Kwan Mo, Donghui Lu, Makoto Hashimoto, Thomas P. Devereaux, Zhi-Xun Shen
2020 Proceedings of the National Academy of Sciences of the United States of America  
The resistance of a conventional insulator diverges as temperature approaches zero. The peculiar low-temperature resistivity saturation in the 4f Kondo insulator (KI) SmB6 has spurred proposals of a correlation-driven topological Kondo insulator (TKI) with exotic ground states. However, the scarcity of model TKI material families leaves difficulties in disentangling key ingredients from irrelevant details. Here we use angle-resolved photoemission spectroscopy (ARPES) to study FeSb2, a
more » ... FeSb2, a correlated d-electron KI candidate that also exhibits a low-temperature resistivity saturation. On the (010) surface, we find a rich assemblage of metallic states with two-dimensional dispersion. Measurements of the bulk band structure reveal band renormalization, a large temperature-dependent band shift, and flat spectral features along certain high-symmetry directions, providing spectroscopic evidence for strong correlations. Our observations suggest that exotic insulating states resembling those in SmB6 and YbB12 may also exist in systems with d instead of f electrons.
doi:10.1073/pnas.2002361117 pmid:32571928 fatcat:vruwaljv3fgsbojz5bq3vykvgi