Trion Formation Dynamics in Monolayer Transition Metal Dichalcogenides

TL;DR

This study investigates how charged excitons (trions) form in doped monolayer TMDs, revealing that their formation time varies with excitation energy and indicating the presence of localized and delocalized excitons.

Contribution

It provides new insights into the dynamics of trion formation in TMDs and suggests the existence of an exciton mobility edge due to disorder effects.

Findings

Trion formation occurs on a picosecond timescale.

Trion formation time increases as pump energy shifts lower.

Evidence for localized and delocalized excitons in TMDs.

Abstract

We report charged exciton (trion) formation dynamics in doped monolayer transition metal dichalcogenides (TMDs), specifically molybdenum diselenide (MoSe2), using resonant two-color pump-probe spectroscopy. When resonantly pumping the exciton transition, trions are generated on a picosecond timescale through exciton-electron interaction. As the pump energy is tuned from the high energy to low energy side of the inhomogeneously broadened exciton resonance, the trion formation time increases by ~ 50%. This feature can be explained by the existence of both localized and delocalized excitons in a disordered potential and suggests the existence of an exciton mobility edge in TMDs. The quasiparticle formation and conversion processes are important for interpreting photoluminescence and photoconductivity in TMDs.