The novel properties of epitaxial bismuth ultra-thin films on superconducting substrate NbSe$_2$

Bismuth is theoretically predicted to be a quantum spin Hall (QSH) system. Such a QSH system, interesting itself with the genuine spin degenerated backscattering forbidden transport property, is also a potential platform to study the 2D topological superconductor with superconductivity induced by proximity effect. The epitaxial growth of ultra-thin Bi(111) film on superconductor NbSe$_{2}$ was investigated by scanning tunneling microscopy(STM) and scanning tunneling spectroscopy(STS). The orientation transition from Bi(110) phase to Bi(111) phase has been observed. One-dimensional topological edge states on the zig-zag edge of Bi(111) bilayers and proximity effect-induced superconductivity were also revealed by STS analysis.