Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 100140, China.
Department of Physics, Zhejiang University , Hangzhou 310027, Zhejiang China.
Nano Lett. 2017 May 10;17(5):3035-3039. doi: 10.1021/acs.nanolett.7b00365. Epub 2017 Apr 20.
Ultrathin freestanding bismuth film is theoretically predicted to be one kind of two-dimensional topological insulators. Experimentally, the topological nature of bismuth strongly depends on the situations of the Bi films. Film thickness and interaction with the substrate often change the topological properties of Bi films. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy or spectroscopy and first-principle calculation, the properties of Bi(111) ultrathin film grown on the NbSe superconducting substrate have been studied. We find the band structures of the ultrathin film is quasi-freestanding, and one-dimensional edge state exists on Bi(111) film as thin as three bilayers. Superconductivity is also detected on different layers of the film and the pairing potential exhibits an exponential decay with the layer thicknesses. Thus, the topological edge state can coexist with superconductivity, which makes the system a promising platform for exploring Majorana Fermions.
理论上预言超薄的自由-standing 铋膜是一种二维拓扑绝缘体。实验上，铋的拓扑性质强烈依赖于铋膜的情况。膜的厚度和与衬底的相互作用经常改变铋膜的拓扑性质。利用角分辨光电子能谱、扫描隧道显微镜或光谱学和第一性原理计算，研究了生长在 NbSe 超导衬底上的 Bi(111)超薄膜的性质。我们发现超薄膜的能带结构是准自由-standing 的，Bi(111)薄膜在三层以下时存在一维边缘态。在薄膜的不同层也检测到超导性，配对势随层厚度呈指数衰减。因此，拓扑边缘态可以与超导共存，这使得该体系成为探索马约拉纳费米子的有前途的平台。
