Tunable inverse topological heterostructure utilizing $(Bi_{1-x}In_{x})_{2}Se_{3}$

TL;DR

This paper introduces a novel inverse topological heterostructure where non-topological layers are sandwiched between topological insulators, allowing tunable coupling and insulating properties for advanced device applications.

Contribution

The study demonstrates the first material system with reversed roles, using $(Bi_{1-x}In_{x})_{2}Se_{3}$ layers between $Bi_2Se_3$, and systematically tunes the coupling from metallic to insulating regimes.

Findings

Tunable coupling between TI layers achieved.

Transition from metallic to insulating regimes demonstrated.

Provides a platform for probing TI coupling and device engineering.

Abstract

In typical topological insulator (TI) systems the TI is bordered by a non-TI insulator, and the surrounding conventional insulators, including vacuum, are not generally treated as part of the TI system. Here, we implement the first material system where the roles are reversed, and the TSS form around the non-TI (instead of the TI) layers. This is realized by growing a layer of the tunable non-TI $(Bi_{1-x}In_{x})_{2}Se_{3}$ in between two layers of the TI $Bi_2Se_3$ using the atomically-precise molecular beam epitaxy technique. On this tunable inverse topological platform, we systematically vary the thickness and the composition of the $(Bi_{1-x}In_{x})_{2}Se_{3}$ layer and show that this tunes the coupling between the TI layers from strongly-coupled metallic to weakly-coupled, and finally to a fully-decoupled insulating regime. This system can be used to probe the fundamental nature of coupling in TI materials and provides a tunable insulating layer for TI devices.