Functionalized Tellurene; a candidate large-gap 2D Topological Insulator

TL;DR

This paper reports that oxygen-functionalized tellurene can be a stable, large-gap 2D topological insulator with potential for room-temperature spintronic applications, featuring exotic quantum properties and strain-engineered tunability.

Contribution

It demonstrates that oxygen functionalization induces topologically non-trivial states in tellurene, a group VI monolayer, with large band gaps and robust quantum properties.

Findings

Large topological band gap (~0.36 eV) in functionalized tellurene.

Presence of isolated Dirac cone along edges indicating topological edge states.

High spin Hall conductivity and non-trivial topological invariants (Z2=1, C=1).

Abstract

The discovery of group IV and V elemental Xene's which exhibit topologically non-trivial characters natively in their honeycomb lattice structure (HLS) has led to extensive efforts in realising analogous behaviour in group VI elemental monolayers. Although; it was theoretically concluded that group VI elemental monolayers cannot exist as HLS but recent experimental evidence suggests otherwise. In this letter we report that, HLS of group VI elemental monolayer (such as, Tellurene) can be realised to be dynamically stable when functionzalised with Oxygen. The functionalization leads to, peculiar orbital filtering effects (OFE) and broken spatial inversion symmetry which gives rise to the non-trivial topological character. The exotic quantum behaviour of this system is characterized by, spin-orbit coupling induced large-gap $\approx$ 0.36 eV with isolated Dirac cone along the edges indicating perspective room temperature spin-transport applications. Further investigations of spin Hall conductivity and the Berry curvatures unravel high conductivity as compared to previously explored Xene's. The non-trivial topological character is quantified in terms of the $\mathbb{Z}_2$ invaraint as $\nu =$ 1 and Chern number $\mathit{C} =$ 1. Also, for practical purposes, we report that, \textit{h}BN/TeO/\textit{h}BN quantum-wells can be strain engineered to realize a sizable non-trivial gap ($\approx$ 0.11 eV). We finally conclude that, functionalization of group VI elemental monolayer with Oxygen gives rise to, exotic quantum properties which are robust against surface oxidation and degradations while providing viable electronic degrees of freedom for spintronic applications.