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

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.