Exciton dynamics in atomically thin MoS2: inter-excitonic interaction and broadening kinetics

TL;DR

This study uses ultrafast spectroscopy to explore how excitons in atomically thin MoS2 interact and broaden, revealing that inter-excitonic interactions significantly influence exciton dynamics and spectral broadening.

Contribution

It provides detailed insights into the inter-excitonic interactions and broadening mechanisms in MoS2, highlighting the dominant role of inter-excitonic scattering over free-carrier scattering.

Findings

Inter-excitonic interactions cause transient blue shifts in excitonic absorption.

B exciton linewidth broadening reduces A exciton spectral amplitude.

Inter-excitonic scattering dominates broadening kinetics at B exciton resonance.

Abstract

We report ultrafast pump-probe spectroscopy examining exciton dynamics in atomically thin MoS2. Spectrally- and temporally-resolved measurements are performed to investigate the interaction dynamics of two important direct-gap excitons (A and B) and their associated broadening kinetics. The two excitons show strongly correlated inter-excitonic dynamic, in which the transient blue-shifted excitonic absorption originates from the internal A-B excitonic interaction. The observed complex spectral response is determined by the exciton collision-induced linewidth broadening; the broadening of the B exciton linewidth in turn lowers the peak spectral amplitude of the A exciton. Resonant excitation at the B exciton energy reveals that inter-excitonic scattering plays a more important role in determining the broadening kinetics than free-carrier scattering.