Anomalously Large Spectral Shifts near the Quantum Tunnelling Limit in Plasmonic Rulers with Subatomic Resolution

摘要: The resonance wavelength of a coupled plasmonic system is extremely sensitive to the distance between its metallic surfaces, resulting in "plasmon rulers". We explore this behavior subnanometer regime using self-assembled monolayers bis-phthalocyanine molecules nanoparticle-on-mirror (NPoM) construct. These allow unprecedented subangstrom control over spacer thickness via choice metal center, gap-size at quantum-mechanical limit enhancement. A dramatic shift plasmon observed as gap size varied from 0.39 0.41 nm. Existing theoretical models are unable account for spectral tuning, which requires inclusion quantum-classical interface, emphasizing need new treatments light subnanoscale.