Discovery of Superconductivity in 2M WS<sub>2</sub> with Possible Topological Surface States.

Fang, Yuqiang; Pan, Jie; Zhang, Dongqin; Wang, Dong; Hirose, Hishiro T; Terashima, Taichi; Uji, Shinya; Yuan, Yonghao et al. · Adv Mater · 2019

basic_science · Level V

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Abstract

Recently the metastable 1T'-type VIB-group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS<sub>2</sub> dubbed "2M" WS<sub>2</sub> , is constructed from 1T' WS<sub>2</sub> monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system. Intrinsic superconductivity is observed in 2M WS<sub>2</sub> with a transition temperature T<sub>c</sub> of 8.8 K, which is the highest among TMDs not subject to any fine-tuning process. Furthermore, the electronic structure of 2M WS<sub>2</sub> is found by Shubnikov-de Haas oscillations and first-principles calculations to have a strong anisotropy. In addition, topological surface states with a single Dirac cone, protected by topological invariant Z<sub>2</sub> , are predicted through first-principles calculations. These findings reveal that the new 2M WS<sub>2</sub> might be an interesting topological superconductor candidate from the VIB-group transition metal dichalcogenides.