Control of Plexcitonic Strong Coupling via Substrate- Mediated Hotspot Nanoengineering

摘要

Plexcitonic strong coupling has ushered in an era of room-temperaturequantum electrodynamics at the nanoscale. Realizing its potential applicationsfrom single-molecule spectroscopy to room-temperature quantum technologieson an industrial level requires scalable and mass-producible plasmonic cavitiesthat provide ease of access and control for quantum emitters. Here, a strategyfor multidimensional hotspot engineering is proposed via a rational selectionof substrates, which facilitates elevation of a gold bowtie nanocavity hotspotto the top of the device and provides a field enhancement of ≈482 (a 1.6-foldincrease compared to a conventional bowtie-on-glass cavity at the bottom ofthe nanogap). The formation mechanism for these antenna modes is discussedfrom the perspective of charge carrier motion; and their advantages, particularlyin view of their dominantly in-plane polarized near-fields, are further elaboratedin a spatiotemporal study of plexcitonic strong coupling, which reveals ultrafastquantum dynamics and potential for applications related to 2D materials whoseexcitonic dipoles are typically oriented in-plane. The conceptual discovery ofthis substrate-enabled hotspot nanoengineering could readily be extended totailor hotspots in other plasmonic platforms, and may inspire a plethora ofnovel research directions from plasmon-enhanced spectroscopy and sensing tothe design of quantum logic gates and quantum metasurfaces.