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arXiv · 2408.16306

High-temperature observation of intralayer, interlayer, and Rydberg excitons in bulk van der Waals alloy single crystals

Pravrati Taank·Asif Ali·Aravind Raji·Ajay K. Poonia·Matthew C. Beard·Ravi Shankar Singh·K. V. Adarsh
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Abstract

Transition metal dichalcogenides (TMDs) exhibit remarkable optical properties due to the diverse number of strongly bound excitons, which can be fine-tuned by alloying. Despite a flurry of research activity in characterizing these excitons, a comprehensive and profound understanding of their behavior with temperature is lacking. Here, we report the rich spectrum of excitonic features within bulk van der Waals alloy Mo$_{0.5}$W$_{0.5}$S$_2$ and Mo$_{0.5}$W$_{0.5}$Se$_2$ single crystals through temperature-dependent reflectance spectroscopy and first-principle calculations. We observed Rydberg excitons and interlayer excitons in both the single crystals. Notably, we provide the first experimental evidence of highly energetic A$^\prime$ and B$^\prime$ excitons in Mo$_{0.5}$W$_{0.5}$S$_2$ at room temperature. The strong carrier-phonon scattering significantly broadens the A$^\prime$, B$^\prime$ and interlayer excitons at room temperature in bulk Mo$_{0.5}$W$_{0.5}$S$_2$ single crystal compared to its selenide. Our findings, supported by density functional theory and Bethe-Salpeter equation calculations, signify the crucial role of carrier-phonon interactions. These results open pathways for next-generation optoelectronic devices and quantum technologies operating at high temperature.

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Pravrati Taank, Asif Ali, Aravind Raji, Ajay K. Poonia, Matthew C. Beard, Ravi Shankar Singh, K. V. Adarsh. 2024-08-29. High-temperature observation of intralayer, interlayer, and Rydberg excitons in bulk van der Waals alloy single crystals. https://doi.org/10.1103/physrevb.110.075205

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