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

• Published in: arXiv.org
• Main Authors: Jorik van de Groep, Li, Qitong, Jung-Hwan, Song, Kik, Pieter G, Brongersma, Mark L
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 05.10.2022
• Subjects: Data processing; Decay rate; Excitons; Line shape; Line spectra; Monolayers; Optical properties; Optoelectronic devices; Photovoltaic cells; Physics - Mesoscale and Nanoscale Physics; Quantum mechanics; Quantum phenomena; Reflection; Room temperature; Signatures; Solar cells; Substrates; Transition metal compounds
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2210.02064

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.