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arXiv · 2502.10150

Single-molecule phosphorescence and intersystem crossing in a coupled exciton-plasmon system

Abhishek Grewal·Hiroshi Imada·Kuniyuki Miwa·Miyabi Imai-Imada·Kensuke Kimura·Rafael Jaculbia·Klaus Kuhnke·Klaus Kern·Yousoo Kim
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Abstract

Scanning the sharp metal tip of a scanning tunneling microscope (STM) over a molecule allows tuning the coupling between the tip plasmon and a molecular fluorescence emitter. This allows access to local variations of fluorescence field enhancement and wavelength shifts, which are central parameters for characterizing the plasmon-exciton coupling. Performing the same for phosphorescence with molecular scale resolution remains a significant challenge. In this study, we present the investigation of phosphorescence from isolated Pt-Phthalocyanine molecules by analyzing tip-enhanced emission spectra in both current-induced and laser-induced phosphorescence. The latter directly monitors singlet-to-triplet state intersystem crossing of a molecule below the tip. The study contributes to a detailed understanding of triplet excitation pathways and their potential control at sub-molecular length scales. Additionally, the coupling of organic phosphors to plasmonic structures is a promising route for improving light-emitting diodes.

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Abhishek Grewal, Hiroshi Imada, Kuniyuki Miwa, Miyabi Imai-Imada, Kensuke Kimura, Rafael Jaculbia, Klaus Kuhnke, Klaus Kern, Yousoo Kim. 2025-06-13. Single-molecule phosphorescence and intersystem crossing in a coupled exciton-plasmon system. https://arxiv.org/abs/2502.10150

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