Quantum spin Hall insulators in centrosymmetric thin films composed from topologically trivial BiTeI trilayers

TL;DR

This paper demonstrates that quantum spin Hall insulators can be engineered in ultra-thin films made from trivial insulators with strong spin-orbit coupling, specifically using centrosymmetric sextuple layers derived from BiTeI trilayers.

Contribution

It introduces a novel approach to realize quantum spin Hall insulators in centrosymmetric thin films constructed from trivial insulators, expanding the design principles for topological materials.

Findings

Centrosymmetric sextuple layers from BiTeI can host quantum spin Hall states.

A strong three-dimensional topological insulator Bi2Te2I2 is designed from these layers.

General principles for creating topological insulators from BiTeX family elements are revealed.

Abstract

The quantum spin Hall insulators predicted ten years ago and now experimentally observed are instrumental for a breakthrough in nanoelectronics due to non-dissipative spin-polarized electron transport through their edges. For this transport to persist at normal conditions, the insulators should possess a sufficiently large band gap in a stable topological phase. Here, we theoretically show that quantum spin Hall insulators can be realized in ultra-thin films constructed from a trivial band insulator with strong spin-orbit coupling. The thinnest film with an inverted gap large enough for practical applications is a centrosymmetric sextuple layer built out of two inversely stacked non-centrosymmetric BiTeI trilayers. This nontrivial sextuple layer turns out to be the structure element of an artificially designed strong three-dimensional topological insulator Bi$_2$Te$_2$I$_2$. We reveal general principles of how a topological insulator can be composed from the structure elements of the BiTeX family (X=I, Br, Cl), which opens new perspectives towards engineering of topological phases.