Observation of dynamic screening in the excited exciton states in multilayered MoS2

Excitonic resonance and binding energies can be altered by controlling the environmental screening of the attractive Coulomb potential. Although this screening response is often assumed to be static, the time evolution of the excitonic quasiparticles manifests a frequency dependence in its Coulomb screening efficacy. In this paper, we investigate a ground (1s) and first excited exciton state (2s) in a multilayered transition metal dichalcogenide (MoS2) upon ultrafast photoexcitation. We explore the dynamic screening effects on the latter and show its resonance frequency is the relevant frequency at which screening from the smaller-sized 1s counterparts is effective. Our finding sheds light on new avenues of external tuning on excitonic properties.