At the verge of topology: vacancy-driven quantum spin Hall in trivial insulators

TL;DR

This paper demonstrates that vacancy-induced interactions in trivial insulators like PtSe2 can create a topologically non-trivial phase with protected metallic channels, expanding the understanding of topological transitions in materials.

Contribution

It introduces a new vacancy-mediated mechanism for inducing topological phases in trivial insulators, supported by ab initio calculations and an effective model.

Findings

Vacancies can induce a topological phase transition in PtSe2.

A large topological gap of 180 meV is created within the pristine gap.

The mechanism enables the formation of protected metallic channels.

Abstract

Vacancies in materials structure -- lowering its atomic density -- take the system closer to the atomic limit, to which all systems are topologically trivial. Here we show a mechanism of mediated interaction between vacancies inducing a topologically non-trivial phase. Within an {\it ab initio} approach we explore topological transition dependence with the vacancy density in transition metal dichalcogenides. As a case of study, we focus on the PtSe$_2$, to which pristine form is a trivial semiconductor with an energy gap of $1.2$\,eV. The vacancies states lead to a large topological gap of $180$\,meV within the pristine system gap. We derive an effective model describing this topological phase in other transition metal dichalcogenide systems. The mechanism driving the topological phase allows the construction of backscattering protected metallic channels embedded in a semiconducting host.