Topological insulator behavior of WS2 monolayer with square-octagon ring structure

We report electronic behavior of an allotrope of monolayer WS2 with a square octagon ring structure, refereed to as (so-WS2) within state-of-the-art density functional theory (DFT) calculations. The WS2 monolayer shows semi-metallic characteristics with Dirac-cone like features around Г. Unlike p-orbital’s Dirac-cone in graphene, the Dirac-cone in the so-WS2 monolayer originates from the d-electrons of the W atom in the lattice. Most interestingly, the spin-orbit interaction associated with d-electrons induce a finite band-gap that results into the metal-semiconductor transition and topological insulator-like behavior in the so-WS2 monolayer. These characteristics suggest the so-WS2 monolayer to be a promising candidate for the next-generation electronic and spintronics devices.