Trion light emission in type-I WSe₂/MoTe₂ van der Waals heterostructures

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are attractive materials to investigate the light-induced many-body excitons. The reduced Coulomb screening leads to a large exciton binding energy, and stacking two or more dissimilar TMDs provides easy way to build van der Waals (vdW) heterostructures. With this features TMDs enables us to study a variety body of excitons such as neutral exciton, charged excitons, type-II interlayer excitons, moiré excitons, and localized excitons. Here we perform photoluminescence (PL), reflection contrast (RC) and photoluminescence excitation (PLE) to investigate vdW type-I heterostructures. We report the spectroscopic identification in type-I heterostructure of trions, a quasiparticle composed of two electrons and a hole. In the heterostructure spectra, we observe a significant enhancement of the MoTe₂ A trion PL emission under the excitation in resonance with the WSe₂ trion resonances. The enhancement is interpreted as a transfer effect arising from trions initially created in either layer. We suggest that the trions generated in WSe₂ have a great influence on the MoTe₂ trion emission. Our results show possibilities for fundamental studies of many-body interactions in 2D TMDs heterostructures.