Alloys*

Valleytronics is a driving motivation behind the exploration of transition metal dichalcogenides (TMDs). However, few studies have explored valley-dependent phenomena in TMD alloys. This is an important knowledge gap as the flexibility provided by alloying may be vital for the application of TMDs. We study the valleytronic properties of monolayer WSe_2(1-x)Te_2x (x=0…1), an alloy system where the endpoints WSe₂ and WTe₂ occupy different structural phases (H and 1T’, respectively). As the Te composition x is increased, the alloy undergoes a semiconductor-semimetal phase transition, which we explore with temperature-dependent Raman and photoluminescence (PL) measurements. We find that Te incorporation activates new Raman modes, while also leading to non-monotonic shifts in the neutral exciton and trion energies and linewidths. Temperature-dependent PL measurements show valley polarization and valley coherence survive when Te doping is less than ~23%, above which valley polarization disappears while valley coherence gradually decreases. These findings demonstrate that valleytronic properties can be robust against disorder and illustrate the potential of two-dimensional alloys for valleytronic technologies.