Wang Zhichang, Liu Xiaoqiang, Zhu Jianqi, You Sifan, Bian Ke, Zhang Guangyu, Feng Ji, Jiang Ying
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
Beijing National Laboratory for Condensed Matter Physics and, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; School of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610101, China.
Sci Bull (Beijing). 2019 Dec 15;64(23):1750-1756. doi: 10.1016/j.scib.2019.10.004. Epub 2019 Oct 10.
Monolayer transition metal dichalcogenides (TMDCs) with the 1T' structure are a new class of large-gap two-dimensional (2D) topological insulators, hosting topologically protected conduction channels on the edges. However, the 1T' phase is metastable compared to the 2H phase for most of 2D TMDCs, among which the 1T' phase is least favored in monolayer MoS. Here we report a clean and controllable technique to locally induce nanometer-sized 1T' phase in monolayer 2H-MoS via a weak Argon-plasma treatment, resulting in topological phase boundaries of high density. We found that the stabilization of 1T' phase arises from the concerted effects of S vacancies and the tensile strain. Scanning tunneling spectroscopy (STS) clearly reveals a spin-orbit band gap (~60 meV) and topologically protected in-gap states residing at the 1T'-2H phase boundary, which are corroborated by density-functional theory (DFT) calculations. The strategy developed in this work can be generalized to a large variety of TMDCs materials, with potentials to realize scalable electronics and spintronics with low dissipation.
具有1T'结构的单层过渡金属二硫属化物（TMDCs）是一类新型的大带隙二维（2D）拓扑绝缘体，其边缘存在拓扑保护的传导通道。然而，对于大多数二维TMDCs而言，与2H相相比，1T'相是亚稳态的，其中在单层MoS中1T'相最不稳定。在此，我们报道了一种通过弱氩等离子体处理在单层2H-MoS中局部诱导纳米尺寸1T'相的清洁且可控的技术，从而产生高密度的拓扑相边界。我们发现1T'相的稳定源于S空位和拉伸应变的协同作用。扫描隧道谱（STS）清楚地揭示了一个自旋轨道带隙（约60 meV）以及位于1T'-2H相边界处的拓扑保护的带隙内态，这得到了密度泛函理论（DFT）计算的证实。这项工作中开发的策略可以推广到多种TMDCs材料，具有实现低功耗可扩展电子学和自旋电子学的潜力。
