Tuning the symmetry and electronic and topological properties of two-dimensional transition metal dichalcogenides by alloying

Using first principles calculations in combination with combined with evolutionary algorithms, we identify stable and metastable configurations of a two-dimensional alloy of WS_2xTe_2(1-x) with high thermodynamic stability. The alloy system undergoes the phase transition of its crystal symmetry with the changes in its stoichiometry between S and Te. At the same time, the alloy induces a semiconductor-to-metal transition. Furthermore, a metal states induced by the alloy can become a topological insulator. We discuss the origin of the transitions of their symmetry and the electronic and topological properties, as well as the energetics and kinetics of the alloying processes for experimental synthesis. Our work provides a synthesis route for the realization of 2D TMDs with versatile properties.