Probing FeSi, a d-electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves

Abstract

Recently, evidence for a conducting surface state below 19 K was reported for the correlated d-electron small gap semiconductor FeSi. In the work reported herein, the conducting surface state and the bulk phase of FeSi were probed via electrical resistivity measurements as a function of temperature T, magnetic field B to 60 T and pressure P to 7.6 GPa, and by means of a magnetic field modulated microwave spectroscopy (MFMMS) technique. The properties of FeSi were also compared to those of the Kondo insulator SmB6 to address the question of whether FeSi is a d-electron analogue of an f-electron Kondo insulator and, in addition, a topological Kondo insulator. The overall behavior of the magnetoresistance MR of FeSi at temperatures above and below the onset temperature (T_S) 19 K of the conducting surface state is similar to that of SmB6. The two energy gaps, inferred from the resistivity data in the semiconducting regime, increase with pressure up to about 7 GPa, followed by a drop which coincides with a sharp suppression of T_S. This behavior is similar to that reported for SmB6, except that the two energy gaps in SmB6 decrease with pressure before dropping abruptly at T_S. The MFMMS measurements showed a sharp feature at T_S (19 K) for FeSi, but no such feature was observed at T_S 4.5 K for SmB6. The absence of a feature at T_S for SmB6 may be due to experimental issues and will be the subject of a future investigation.

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• Topological Insulator Materials
• Topological Kondo Insulators
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• Probing FeSi, a d-electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves
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• Pressure-Driven Valence Increase and Metallization in Kondo Insulator Ce${}_3$Bi${}_4$Pt${}_3$
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Cited by in corpus (4)

• Probing FeSi, a d-electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves
• Extraordinary Bulk Insulating Behavior in the Strongly Correlated Materials FeSi and FeSb${}_2$
• Lieb-Schultz-Mattis constraints for the insulating phases of the one-dimensional SU($N$) Kondo lattice model
• Disordered 2D ferromagnetism at the surface of FeSi