Searching for Large-gap Quantum Spin Hall Insulators: Boron-Nitride/(Pb, Sn)/{\alpha}-Al2O3 Sandwich Structures

TL;DR

This paper predicts that honeycomb lead monolayers on Al2O3 substrates can be topologically non-trivial with large band gaps, and proposes using h-BN layers for protection, advancing practical 2D topological insulators.

Contribution

It introduces a new method to stabilize large-gap 2D topological insulators using Al2O3 substrates and h-BN protection layers, which was not previously demonstrated.

Findings

Pb/Al2O3 has a band gap of ~0.27 eV

h-BN can protect topological states of Pb/Al2O3 and Sn/Al2O3

Potential for designing practical 2D TIs

Abstract

Topological insulators hold great potential for efficient information processing and storage. Using density functional theory calculations, we predict that a honeycomb lead monolayer can be stabilized on the Al2O3 (0001) substrate and becomes topologically non-trivial with a sizeable band gap (~0.27 eV). Furthermore, we propose to use hexagonal boron-nitride (h-BN) monolayer as a protection for the topological states of Pb/Al2O3 and Sn/Al2O3. Our findings suggest new possibilities for designing and protecting two-dimensional TIs for practical applications.