# The interplay between excitons and trions in a monolayer of MoSe$_2$

## TL;DR

This study investigates how free carriers influence exciton and trion properties in a MoSe₂ monolayer, revealing that increased electron density enhances trion binding energy, supported by experimental and theoretical analysis.

## Contribution

It introduces a variational model accounting for screening and phase space filling effects to explain the impact of free carriers on excitonic complexes.

## Key findings

- Trion binding energy increases with electron density.
- Photoluminescence spectra show power- and time-resolved changes.
- Theoretical model reproduces experimental observations.

## Abstract

We study the impact of a free carrier reservoir on the optical properties of excitonic and trionic complexes in a MoSe$_2$ monolayer at cryogenic temperatures. By applying photodoping via a non-resonant pump laser the electron density can be controlled in our sample and in turn the exciton and trion densities can be tuned. We find a significant increase of the trion binding energy in the presence of an induced electron gas both in power- and in time-resolved photoluminescence spectra. This behaviour is reproduced within the original variational approach that takes into account both screening and phase space filling effects.