Title: Observation of inhomogeneous plasmonic field distribution in a nanocavity

Authors: Chao-Yu Li, Sai Duan, Bao-Ying Wen, Song-Bo Li, Murugavel Kathiresan, Li-Qiang Xie, Shu Chen, Jason R. Anema, Bing-Wei Mao, Yi Luo, Zhong-Qun Tian & Jian-Feng Li

Abstract: The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres^1,2,3,4,5,6. Plasmon-enhanced applications include advanced spectroscopies^7,8,9,10, optomechanics¹¹, optomagnetics¹² and biosensing^{13,14,15,16,17}. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully.

Full-Link: https://www.nature.com/articles/s41565-020-0753-y