We have investigated the structures and electronic properties of ultra-thin Bi(110) films grown on an s-wave superconductor substrate using low-temperature scanning tunneling microscopy and spectroscopy. Remarkably, our experimental results validate the theoretical predictions that the manipulation of Bi(110) surface atom buckling can control the topological phase transition. Notably, we have observed robust unreconstructed edge states at the edges of both 3-bilayer (BL) and 4-BL Bi(110) films, with the 4-BL film displaying stronger edge state intensity and a smaller degree of atomic buckling. First-principle calculations further substantiate these findings, demonstrating a gradual reduction in buckling as the film thickness increases, with average height differences between two Bi atoms of approximately 0.19 {\AA}, 0.10 {\AA}, 0.05 {\AA}, and 0.00 {\AA} for the 1-BL, 2-BL, 3-BL, and 4-BL Bi(110) films, respectively. When Bi films are larger than 2 layers, the system changes from a trivial to a non-trivial phase. This research sets the stage for the controlled realization of topological superconductors through the superconducting proximity effect, providing a significant platform for investigating Majorana zero modes and fabricating quantum devices.
@article{arxiv.2410.19369,
title = {Tunable topological edge states in black phosphorus-like Bi(110)},
author = {Chen Liu and Shengdan Tao and Guanyong Wang and Hongyuan Chen and Bing Xia and Hao Yang and Xiaoxue Liu and Liang Liu and Yaoyi Li and Shiyong Wang and Hao Zheng and Canhua Liu and Dandan Guan and Yunhao Lu and Jin-feng Jia},
journal= {arXiv preprint arXiv:2410.19369},
year = {2024}
}