Epitaxial growth of BP-like Bi(1 1 0) with moiré pattern and potential topological edge state

Abstract

Black-phosphorus-like (BP-like) Bi(110) thin film, a potential large band gap two-dimensional (2D) topological insulator (TI) candidate that hosts a non-dissipative topological edge state, has attracted a lot of attention in recent years. However, the Bi(110) thin film with a large bulk band gap and topological edge states has not been definitely confirmed experimentally. Here, high-quality BP-like Bi(110) thin film is epitaxially grown on a semiconductor SnSe substrate. Employing scanning tunneling microscopy/spectroscopy (STM/S), the BP-like structure was determined, and the corresponding electronic structure was also investigated. In addition, a distinct quasi-squared moiré pattern was observed, and the electronic states far away from Fermi energy in the 1BL Bi(110) film are significantly modulated by the moiré pattern spatially; instead, the electronic states near the Fermi energy are less influenced by the moiré pattern. Importantly, we also observed the enhanced states at the edge of 1BL and 2BL Bi(110) films, especially for 2BL film, with a clear sign of edge state peak extending to 2 nm depth, suggesting that 2BL BP-like Bi(110) on SnSe is a potential 2D TI. As a result, our research provides a platform for the further topological investigation of the BP-like Bi(110) thin film.