Identification of Exciton Complexes in Charge-Tunable Janus WSeS Monolayers

Janus transition-metal dichalcogenide monolayers are artificial materials, where one plane of chalcogen atoms is replaced by chalcogen atoms of a different type. Theory predicts an in-built out-of-plane electric field, giving rise to long-lived, dipolar excitons, while preserving direct-band g a p optical tran-sitions in a uniform potential landscape. Previous Janus studies had broad photoluminescence (>18 meV) spectra obfusca t i n g their specific excitonic origin. Here, we identif y the neutral and the negatively charged inter-and intravalley exciton transitions in Janus WSe S monolayers with similar to 6 meV optical line widths. We integrate Janus monolayers into vertical heterostructures, allowing doping control . Magneto-optic measurements indicate that monolayer WSe S has a direct bandgap at the K points. Our results pave the way for applications such as nanoscale sensing, which relies on resolv i n g excitonic energy shifts, and the development of Janus-based optoelectronic devices, which requires charge-state control and integration into vertical heterostructures.

Automated summary

Janus transition-metal dichalcogenide monolayers are artificial materials with unique properties, such as long-lived, dipolar excitons and direct-band gap optical transitions. In this study, the specific excitonic origin of Janus WSe S monolayers with narrow optical line widths is identified. The integration of Janus monolayers into vertical heterostructures allows for doping control and the development of optoelectronic devices. These findings have important implications for nanoscale sensing and the advancement of Janus-based technology.