Topological surface state and odd-parity magnetoresistance induced in narrow-gap semiconductor α-Sn by magnetic proximity effect

Combing magnetism into topological material platform attracts significant attention due to the potential of realizing low power consumption and error-robust electronic devices. In this work, we show that both ferromagnetism and band inversion can be established simultaneously in a trivial insulating material by using the magnetic proximity effect (MPE) from a neighbouring ferromagnetic layer [1]. The system under study is a heterostructure consisting of 5-nm-thick FeO_x / 1 monolayer of FeAs / 3-nm-thick α-Sn grown on an InSb (001) substrate by molecular beam epitaxy. We observe clear Shubnikov–de Haas oscillations, which show that there is linear band dispersion with high mobility (28900 cm²/Vs) in the heterostructure even though a 3-nm-thick α-Sn single layer is a trivial semiconductor [2]. Furthermore, the structure shows a large odd-parity magnetoresistance (~100%), manifesting time reversal breaking in the α-Sn layer induced by the MPE. Our first-principles calculations reveal that band inversion indeed occurs in this heterostructure, suggesting that the observed linear band is a topological surface state within this inverted gap. This work significantly expands the foundation for realizing magnetic topological materials in a myriad of trivial narrow-gap semiconductors.

[1] D. Kurebayashi, & K. Nomura, J. Phys. Soc. Jpn. 83, 063709 (2014).

[2] L. D. Anh, K. Takase et al. Adv. Mater. 33, 2104645 (2021).