Tuning the Edge States of Topological Crystalline Insulator Bismuthene via Substrate Effects

One of the key challenges in design of devices bases on topological materials is to conveniently turn the surface and edge states on and off. Two-dimensional (2D) topological crystalline insulators (TCI) are ideal materials for achieving this switch, as their edge states can be turned on/off by applying a symmetry-breaking field. However, it remains unresolved how 2D TCI phases can be integrated in experimental devices due to the difficulty in synthesis and the complex interactions between TCI and underlying substrates. In this theoretical study based on first principles calculations and Wannier tight-binding models, we show that the edge states of TCI bismuthene can be stabilized on some substrates (e.g. h-BN and SiC) when the stacking pattern does not break mirror symmetry. We can achieve fine tuning of the edge states of bismuthene by applying strain or an external electric field. This research provides guidelines for selection of appropriate substrates for the experimental realization of topological edge states and the methodology to tune the edge states in 2D TCIs.