Topological surface states induced by the magnetic proximity effect

TL;DR

This paper demonstrates that ferromagnetism and topological surface states can be induced simultaneously in a trivial insulator via magnetic proximity effect, expanding possibilities for magnetic topological materials.

Contribution

It introduces a novel method to create topological surface states in trivial insulators through magnetic proximity effect without requiring intrinsic topological properties.

Findings

Linear band dispersion observed in heterostructure

Band inversion confirmed by first principles calculations

Topological surface state identified within the inverted gap

Abstract

The combination of magnetism and topological properties in one material platform is attracting significant attention due to the potential of realizing low power consumption and error-robust electronic devices. Common practice is to start from a topological material with band inversion and incorporates ferromagnetism via chemical doping or magnetic proximity effect (MPE). In this work, we show that a topological material is not necessary and that both ferromagnetism and band inversion can be established simultaneously in a trivial insulating material by MPE from a neighbouring ferromagnetic layer. This novel route is demonstrated using quantum transport measurements and first principles calculations in a heterostructure consisting of 5 nm thick FeOx/1 monolayer of FeAs/ 3 nm thick alpha Sn. The Shubnikov de Haas oscillations show that there is linear band dispersion with high mobility in the heterostructure even though a 3 nm thick alpha Sn single layer is a trivial semiconductor. Furthermore, 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.