Towards Non-van der Waals 2D Topological Insulators

TL;DR

This paper explores the impact of spin-orbit coupling on non-van der Waals 2D materials, revealing topological insulator properties in certain compounds through electronic structure analysis and topological invariant calculations.

Contribution

It provides the first detailed investigation of SOC effects on non-van der Waals 2D materials, identifying topological insulator behavior in specific compounds.

Findings

SbTlO3 exhibits a large SOC-induced band splitting of 229 meV.

Substituting Tl with Pb in SbTlO3 shifts the band-inverted feature to the Fermi level.

Edge state analysis confirms the topological nature of the band splitting in SbPbO3.

Abstract

Non-van der Waals two-dimensional (2D) materials derived from strongly bonded non-layered crystals have recently emerged as a novel and rising platform for nanoscale research. While uncovering and tuning their (opto-)electronic, catalytic, and magnetic properties has been the focus of intense research, the impact of spin-orbit coupling (SOC) onto their electronic structure has not yet been explored in detail. Studying these effects is, however, particularly relevant due to their surface cation termination and the presence of heavy elements in several representative compounds. Here, we investigate the effect of SOC onto the electronic structure of 2D AgBiO3, NaBiO3, and SbTlO3. While the first two systems show negligible band renormalization upon inclusion of relativistic effects around the band gap, SbTlO3 showcases a large SOC induced splitting (229meV) for the lowest conduction bands associated with a band inversion. Substitution of Tl with Pb forming SbPbO3 brings the band-inverted feature to the Fermi level. Analysis of topological invariants and investigation of edge states of zig-zag and armchair ribbons within the 200meV gap confirms the topological nature of the band splitting. Our work thus establishes a foundation for the systematic study of robust non-van der Waals 2D topological insulators.