Interplay of valley polarized dark trion and dark exciton-polaron in monolayer WSe2

TL;DR

This paper investigates how dark excitons and exciton-polarons in monolayer WSe2 are affected by many-body interactions and Fermi sea screening, revealing the evolution of these effects with exciton density and their implications for 2D electronic correlations.

Contribution

It provides new insights into the Fermi sea dressing of dark excitons and the intervalley coupling mediated by many-body interactions in monolayer WSe2.

Findings

Valley-polarized dark excitons show density-dependent photoluminescence shifts.

Onset of strong Fermi sea interactions at a critical carrier density.

Evidence of intervalley coupling between dark trions and exciton-polarons.

Abstract

The interactions between charges and excitons involve complex many-body interactions at high densities. The exciton-polaron model has been adopted to understand the Fermi sea screening of charged excitons in monolayer transition metal dichalcogenides. The results provide good agreement with absorption measurements, which are dominated by dilute bright exciton responses. Here we investigate the Fermi sea dressing of spin-forbidden dark excitons in monolayer WSe2. With a Zeeman field, the valley-polarized dark excitons show distinct p-doping dependence in photoluminescence when the carriers reach a critical density. This density can be interpreted as the onset of strongly modified Fermi sea interactions and shifts with increasing exciton density. Through valley-selective excitation and dynamics measurements, we also infer an intervalley coupling between the dark trions and exciton-polarons mediated by the many-body interactions. Our results reveal the evolution of Fermi sea screening with increasing exciton density and the impacts of polaron-polaron interactions, which lay the foundation for understanding electronic correlations and many-body interactions in 2D systems.