Direct Observation of the Topological Surface State in the Topological Superconductor 2M-WS.

The quantum spin Hall (QSH) effect has attracted extensive research interest because of the potential applications in spintronics and quantum computing, which is attributable to two conducting edge channels with opposite spin polarization and the quantized electronic conductance of 2/. Recently, 2M-WS, a new stable phase of transition metal dichalcogenides with a 2M structure showing a layer configuration identical to that of the monolayer 1T' TMDs, was suggested to be a QSH insulator as well as a superconductor with a critical transition temperature of around 8 K. Here, high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES are applied to investigate the electronic and spin structure of the topological surface states (TSS) in the superconducting 2M-WS. The TSS exhibit characteristic spin-momentum-locking behavior, suggesting the existence of long-sought nontrivial topological states therein. We expect that 2M-WS with coexisting superconductivity and TSS might host the promising Majorana bound states.