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Title: Probing FeSi, a d -electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves
Recently, evidence for a conducting surface state (CSS) below 19 K was reported for the correlatedd-electron small gap semiconductor FeSi. In the work reported herein, the CSS and the bulk phase of FeSi were probed via electrical resistivity ρ measurements as a function of temperatureT, magnetic fieldBto 60 T, and pressurePto 7.6 GPa, and by means of a magnetic field-modulated microwave spectroscopy (MFMMS) technique. The properties of FeSi were also compared with those of the Kondo insulator SmB6to address the question of whether FeSi is ad-electron analogue of anf-electron Kondo insulator and, in addition, a “topological Kondo insulator” (TKI). The overall behavior of the magnetoresistance of FeSi at temperatures above and below the onset temperatureTS= 19 K of the CSS is similar to that of SmB6. The two energy gaps, inferred from the ρ(T) data in the semiconducting regime, increase with pressure up to about 7 GPa, followed by a drop which coincides with a sharp suppression ofTS. Several studies of ρ(T) under pressure on SmB6reveal behavior similar to that of FeSi in which the two energy gaps vanish at a critical pressure near the pressure at whichTSvanishes, although the energy gaps in SmB6initially decrease with pressure, whereas in FeSi they increase with pressure. The MFMMS measurements showed a sharp feature atTS≈ 19 K for FeSi, which could be due to ferromagnetic ordering of the CSS. However, no such feature was observed atTS≈ 4.5 K for SmB6.  more » « less
Award ID(s):
1810310
PAR ID:
10468043
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
NSF PAR
Date Published:
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
120
Issue:
8
ISSN:
0027-8424
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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