Interfacial-state coupling induced topological phase transitions in SnTe (110) thin film

TL;DR

This paper demonstrates how interfacial-state coupling in SnTe (110) thin films induces topological phase transitions, enabling tunable quantum phases with potential applications in electronics and spintronics.

Contribution

It reveals the role of valley-contrasting couplings and film thickness in controlling topological phases in SnTe thin films, introducing a method for tunable topological phase engineering.

Findings

Surface-state coupling varies with film thickness.

Transition between topological crystalline insulator and quantum spin Hall insulator.

Edge-state couplings induce topological phase transitions in nanoribbons.

Abstract

A defining feature of topological insulating phases is symmetry-protected interfacial Dirac states. SnTe is a representative topological crystalline insulator, of which (110) thin films have two symmetry-unrelated valleys of interfacial states. With the help of valley-contrasting couplings of interfacial states, we design various two-dimensional topological phases in (110) SnTe thin film systems. Our first-principles calculations demonstrate that surface-state coupling strengths of two valleys independently vary with the thickness of the thin film, leading to both two-dimensional topological crystalline insulator and quantum spin Hall insulator. Most interestingly, by constructing a nanoribbon array of SnTe thin film, edge-state couplings of nanoribbons can further induce topological phase transition between the above topological phases with high tunability, which offers multi-mode quantum transport with potential use in electronic and spintronic devices.