Rydberg Excitons and Trions in Monolayer MoTe<sub>2</sub>.

Biswas, Souvik; Champagne, Aurélie; Haber, Jonah B; Pokawanvit, Supavit; Wong, Joeson; Akbari, Hamidreza; Krylyuk, Sergiy; Watanabe, Kenji et al. · ACS Nano · 2023

basic_science · Level V

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Abstract

Monolayer transition metal dichalcogenide (TMDC) semiconductors exhibit strong excitonic optical resonances, which serve as a microscopic, noninvasive probe into their fundamental properties. Like the hydrogen atom, such excitons can exhibit an entire Rydberg series of resonances. Excitons have been extensively studied in most TMDCs (MoS<sub>2</sub>, MoSe<sub>2</sub>, WS<sub>2</sub>, and WSe<sub>2</sub>), but detailed exploration of excitonic phenomena has been lacking in the important TMDC material molybdenum ditelluride (MoTe<sub>2</sub>). Here, we report an experimental investigation of excitonic luminescence properties of monolayer MoTe<sub>2</sub> to understand the excitonic Rydberg series, up to 3s. We report a significant modification of emission energies with temperature (4 to 300 K), thereby quantifying the exciton-phonon coupling. Furthermore, we observe a strongly gate-tunable exciton-trion interplay for all the Rydberg states governed mainly by free-carrier screening, Pauli blocking, and band gap renormalization in agreement with the results of first-principles GW plus Bethe-Salpeter equation approach calculations. Our results help bring monolayer MoTe<sub>2</sub> closer to its potential applications in near-infrared optoelectronics and photonic devices.