Recently, an article in field of topological material entitled "Coexistence of Robust Edge States and Superconductivity in Few-Layer Stanene" has been published on Physical Review Letters (Editor's suggestion), which is a collaborated result between Jinfeng Jia's group (Shanghai Jiaotong University) and Zhenyu Zhang and Ping Cui's group (University of Science and Technology of China).
Graphene-like 2D materials are potential topological insulators possessing simple structure and tunable electronic properties. Among them, stanene, the tin analogue of graphene, stands out via intrinsically strong spin-orbital coupling and potential to be superconducting. Yet to date, convincing evidence of topological edge states in stanene remains to be seen, let alone the coexistence with superconductivity, owing to the bottleneck of growing high-quality stanene films.
Figure 1. (a) Topographic image of stanene film. (b) Typical tunneling spectra taken at the film edges and within the bulk. (c) Spatial distribution and energy window of the edge states.
In this work, high-quality 1-5 layer stanene films are successfully grown on Bi(111) substrate with the help of residual hydrogen functioning as a surfactant. Robust edge states are observed on all different layer stanene films [see Fig.1(b) and Fig.2(a) and (b)]. Theoretical calculations reveal that the synergistic effects between intrinsic nontrivial electronic property of stanene itself and the proximity from Bi substrate account for this robust nontrivial topology against layer thickness. Besides, the bilateral penetration length of the edge states are experimentally found to be small [see Fig. 1(c)], especially for the A edge, which is in favor of the development of topological quantum devices with dense edge channels.
Figure 2. (a) Spatial distributions of different electronic states. (b) Edge states on different layer stanene films. (c) Spatial evolution of superconducting gaps crossing the stanene films edge. (d) Superconducting gaps taken on different layer stanene films.
Furthermore, superconductivity with 2D character has also been detected on different layer stanene films [see Fig. 2 (c) and (d)]. The interplay between strong SOC, nontrivial topology, and superconductivity, together with the versatile tunability by surface functionalization or varying the substrate, collectively make few-layer stanene a fertile ground for studying novel superconductivity and tunable topological properties for potential applications in quantum devices, all based on a single-element system.
The graduated doctor student Chenxiao Zhao is the first author of the paper. Professor Jinfeng Jia and Professor Ping Cui are the co-corresponding authors of the paper. This research is supported by Ministry of Science and Technology of China, NSF of China, the Strategic Priority Research Program of Chinese Academy of Sciences, the Science and Technology Commission of Shanghai Municipality, and Shanghai Jiao Tong University.