Rydberg Excitons and Trions in Monolayer MoTe$_2$

TL;DR

This study investigates the excitonic Rydberg series and exciton-trion interactions in monolayer MoTe$_2$, revealing temperature effects and gate-tunable properties, advancing understanding for optoelectronic applications.

Contribution

First detailed experimental exploration of excitonic Rydberg states and exciton-trion dynamics in monolayer MoTe$_2$, supported by first-principles calculations.

Findings

Observation of Rydberg series up to 3s in MoTe$_2$

Temperature-dependent emission energies and exciton-phonon coupling

Gate-tunable exciton-trion interplay influenced by free carriers

Abstract

Monolayer transition metal dichalcogenide (TMDC) semiconductors exhibit strong excitonic optical resonances which serve as a microscopic, non-invasive 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$_2$, MoSe$_2$, WS$_2$ and WSe$_2$), but detailed exploration of excitonic phenomena has been lacking in the important TMDC material molybdenum ditelluride (MoTe$_2$). Here, we report an experimental investigation of excitonic luminescence properties of monolayer MoTe$_2$ to understand the excitonic Rydberg series, up to 3s. We report significant modification of emission energies with temperature (4K to 300K), 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$_2$ closer to its potential applications in near-infrared optoelectronics and photonic devices.