Topological superconductivity at the edge of transition-metal dichalcogenides

Time-reversal breaking topological superconductors are new states of matter which can support Majorana zero modes at the edge. In this Rapid Communication, we propose a different realization of one-dimensional topological superconductivity and Majorana zero modes. The proposed system consists of a monolayer of transition-metal dichalcogenides M X-2 (M = Mo, W; X = S, Se) on top of a superconducting substrate. Based on first-principles calculations, we show that a zigzag edge of the monolayer M X-2 terminated by a metal atom M has edge states with strong spin-orbit coupling and spontaneous magnetization. By proximity coupling with a superconducting substrate, topological superconductivity can be induced at such an edge. We propose NbS2 as a natural choice of substrate, and estimate the proximity induced superconducting gap based on first-principles calculation and a low energy effective model. As an experimental consequence of our theory, we predict that Majorana zero modes can be detected at the 120 degrees corner of a M X-2 flake in proximity to a superconducting substrate.