Quantum Mechanics in Plasmonic Nanocavities: from Theory to Applications

Quantum mechanical effects in plasmonic nanocavities have attracted strong interest in the last two decades, related to both their experimental realization and implementation in technological applications, and to the challenges that need to be overcome in their theoretical modeling. This review summarizes the basic theories of quantum plasmonics, its modeling strategies, and the material systems that support it. Particularly it is focused on recent progress in quantum plasmonics based on the nanoparticle-on-mirror (NPoM) structure, i.e., plasmonic nanoparticles separated from an underlying metallic substrate via an ultrathin spacer, which provides an elegant route toward cost-effective fabrication of a large number of similar plasmonic cavities. A dramatic shift of research trends is seen from basic modeling to applications in nano-optics, polaritonics, chemistry, and biosensing, gradually making the transition from fundamental, curiosity-driven research to applied science.