Metallic surface states in a correlated d-electron topological Kondo insulator candidate FeSb<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 32571928.
- Also identified by DOI 10.1073/pnas.2002361117 and PMC identifier 7354925.
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Abstract
The resistance of a conventional insulator diverges as temperature approaches zero. The peculiar low-temperature resistivity saturation in the 4f Kondo insulator (KI) SmB<sub>6</sub> 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 FeSb<sub>2</sub>, 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 SmB<sub>6</sub> and YbB<sub>12</sub> may also exist in systems with d instead of f electrons.