A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects

TL;DR

This paper predicts a new 2D topological insulator, BiCN, with a giant band gap of about 1 eV, stable on certain substrates, and robust under strain and electric fields, offering a promising platform for topological phases.

Contribution

The study introduces BiCN as a novel 2D topological insulator with a large SOC gap and demonstrates substrate effects and robustness, advancing 2D topological material research.

Findings

BiCN is a thermodynamically stable 2D topological insulator with a ~1 eV gap.

Monolayer h-BN and MoS2 are suitable substrates that preserve BiCN's topological properties.

Topological properties of BiCN are robust against strain and electric fields.

Abstract

Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (? 1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van derWaals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases.