Quantum Spin-quantum Anomalous Hall Effect with Tunable Edge States in Sb Monolayer-based Heterostructures

TL;DR

This paper predicts a new topological insulator in Sb monolayer heterostructures exhibiting tunable edge states with potential applications in electronics, spintronics, and valleytronics, using ab initio and tight-binding models.

Contribution

It introduces the quantum spin-quantum anomalous Hall (QSQAH) effect in SbH heterostructures and demonstrates tunable edge states through substrate-induced exchange fields and external controls.

Findings

A topologically nontrivial band gap up to 35 meV is achieved.

Dissipationless chiral and spin edge states are identified.

Edge states can be manipulated via polarization and chemical modifications.

Abstract

A novel topological insulator with tunable edge states, called quantum spin-quantum anomalous Hall (QSQAH) insulator, is predicted in a heterostructure of a hydrogenated Sb (SbH) monolayer on a LaFeO3 substrate by using ab initio methods. The substrate induces a drastic staggered exchange field in the SbH film, which plays an important role to generate the QSQAH effect. A topologically nontrivial band gap (up to 35 meV) is opened by Rashba spin-orbit coupling, which can be enlarged by strain and electric field. To understand the underlying physical mechanism of the QSQAH effect, a tight-binding model based on px and py orbitals is constructed. With the model, the exotic behaviors of the edge states in the heterostructure are investigated. Dissipationless chiral charge edge states related to one valley are found to emerge along the both sides of the sample, while low-dissipation spin edge states related to the other valley flow only along one side of the sample. These edge states can be tuned flexibly by polarization-sensitive photoluminescence controls and/or chemical edge modifications. Such flexible manipulations of the charge, spin, and valley degrees of freedom provide a promising route towards applications in electronics, spintronics, and valleytronics.