Disorder of Excitons and Trions in Monolayer MoSe2

TL;DR

This study investigates how disorder affects exciton and trion optical transitions in monolayer MoSe2, revealing their correlated energy variations and the underlying dielectric and bandgap fluctuations.

Contribution

It provides a detailed analysis of disorder effects on excitons and trions in MoSe2, combining hyperspectral imaging with theoretical modeling to identify the disorder's origin.

Findings

Exciton and trion energies are spatially correlated with minimal variation in trion binding energy.

Energy splitting between exciton states varies significantly, indicating disorder impact.

Disorder stems from dielectric and bandgap fluctuations, not electrostatic effects.

Abstract

The optical spectra of transition metal dichalcogenide (TMDC) monolayers are dominated by excitons and trions. Here we establish the dependences of these optical transitions on disorder from hyperspectral imaging of h-BN encapsulated monolayer MoSe2. While both exciton and trion energies vary spatially, these two quantities are almost perfectly correlated, with spatial variation in the trion binding energy of only ~0.18 meV. In contrast, variation in the energy splitting between the two lowest energy exciton states is one order of magnitude larger at ~1.7 meV. Statistical analysis and theoretical modeling reveal that disorder results from dielectric and bandgap fluctuations, not electrostatic fluctuations. Our results shed light on disorder in high quality TMDC monolayers, its impact on optical transitions, and the many-body nature of excitons and trions.