Robust Emission of Dark Trions in WS₂/WSe₂ Heterostructure

Due to their nonzero charge, unique spin texture, and long lifetime, spin-forbidden dark trions of monolayer transition-metal dichalcogenides (TMDs) are promising candidates for quantum simulations and optoelectronics. Although previous reports demonstrated that dark trions could be brightened and controlled via the application of external electric fields, it is desired to gain more insight into the origin of dark trions and manipulate dark trions in an all-optical route as well. By coupling WSe2/WS2 heterostructure to a silver nanowire plasmonic resonator, we observed pronounced emission of dark trions of WS2. More importantly, this dark-trion emission could be maintained at a temperature of 230 K, which is a dramatic increase compared with the existing report of 100 K. Furthermore, we found that interlayer charge transfer played a critical role in the formation of dark trions. We also found that that dark trions exhibited a valley degree of freedom and linear anisotropy.