Impact of substrates and quantum effects on exciton line shapes of 2D semiconductors at room temperature

TL;DR

This paper investigates how substrates and quantum effects influence the exciton spectral line shapes in monolayer TMDs at room temperature, revealing how substrate interference and reflection control can elucidate exciton dynamics.

Contribution

It demonstrates that substrate reflections significantly affect exciton line shapes and shows how reflection measurements with index-matching oils can extract quantum exciton decay rates.

Findings

Substrate interference strongly influences exciton line shapes.

Reflection control enables extraction of excitonic decay and dephasing rates.

Guidance for engineering exciton line shapes in nanophotonic systems.

Abstract

Exciton resonances in monolayer transition-metal dichalcogenides (TMDs) provide exceptionally strong light-matter interaction at room temperature. Their spectral line shape is critical in the design of a myriad of optoelectronic devices, ranging from solar cells to quantum information processing. However, disorder resulting from static inhomogeneities and dynamical fluctuations can significantly impact the line shape. Many recent works experimentally evaluate the optical properties of TMD monolayers placed on a substrate and the line shape is typically linked directly to the material's quality. Here, we highlight that the interference of the substrate and TMD reflections can strongly influence the line shape. We further show how basic, room-temperature reflection measurement allow investigation of the quantum mechanical exciton dynamics by systematically controlling the substrate reflection with index-matching oils. By removing the substrate contribution with a properly chosen oil, we can extract the excitonic decay rates including the quantum mechanical dephasing rate. The results provide valuable guidance for the engineering of exciton line shapes in layered nanophotonic systems.