Direct observation of topological surface state in the topological superconductor 2M-WS2

TL;DR

This study provides direct experimental evidence of topological surface states in superconducting 2M-WS2 using ARPES techniques, revealing potential for realizing Majorana bound states in a material combining topological order and superconductivity.

Contribution

First direct observation of topological surface states in superconducting 2M-WS2, demonstrating spin-momentum locking and topological properties in this new phase.

Findings

Topological surface states exhibit spin-momentum locking.

2M-WS2 shows coexistence of superconductivity and topological surface states.

Potential for hosting Majorana bound states in 2M-WS2.

Abstract

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 2e2/h. Recently, 2M-WS2, a new stable phase of transition metal dichalcogenides with a 2M structure showing an identical layer configuration to that of the monolayer 1T' TMDs, was suggested to be a QSH insulator as well as a superconductor with critical transition temperature 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-WS2. The TSS exhibits characteristic spin-momentum-locking behavior, suggesting the existence of long-sought nontrivial Z2 topological states therein. We expect that 2M-WS2 with co-existing superconductivity and TSS might host the promising Majorana bound states.