Strong coupling of single molecules in plasmonic nano- and pico-cavities*

Coupling between plasmonic metal nano-components generates strongly red-shifted resonances combined with intense local field amplification on the nanoscale. This allows directly seeing individual molecules as well as excitations in monolayer semiconductors. We have explored plasmonic coupling which can be tuned dynamically, through reliable bottom-up self-assembly using the nanoparticle-on-mirror geometry (NPoM) [1-5]. We recently demonstrated how precisely placed individual molecules can be strongly coupled to these ultralow volume plasmonic cavities as well as how they act as optomechanical constructs with enormously enhanced coupling. We also demonstrate the possibility to track few molecules using the extreme enhancements. We are able to watch individual electrons hopping onto and off molecules in the gap, and watch redox processes in real time.

[1] Nature 491, 574 (2012); [2] Nature Comm. 5, 4568 (2014); [3] Nature Comm. 5, 3448 (2014); [4] Nature 535, 127 (2016); [5] Science 354, 726 (2016)