Discovery of Superconductivity in 2M WS2 with Possible Topological Surface States. Issue 30 (3rd June 2019) - Fang, Yuqiang
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 WS2 dubbed "2M" WS2, is constructed from 1T′ WS2 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 WS2 with a transition temperature T c of 8.8 K, which is the highest among TMDs not subject to any fine‐tuning process. Furthermore, the electronic structure of 2M WS2 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 Z2, are predicted through first‐principles calculations. These findings reveal that the new 2M WS2 might be an interesting topological superconductor candidate from the VIB‐group transition metal dichalcogenides. Abstract : A new crystal structure of WS2, 2M, is reported. It belongs to the 1T′‐phase family, members of which exhibit W–W zigzag chains along the b axis. Superconductivity with T c of 8.8 K is reported in these 2M WS2 crystals. Moreover, calculations show that a topological surface state exists on the their surface, making them potential candidates for topological superconductors.