Optical spectroscopy in plasmonic cavities has proven to be extremely sensitive to atomic-scale features which ultimate determine optoelectronic interactions within the gaps. In this extreme regime, classical theories fail to address the fine details of the interaction between molecular excitations and plasmons, and thus more sophisticated quantum theories are needed to correctly interpret molecular spectroscopy signals. Several examples of how atomically-resolved molecular spectroscopy can be achieved in plasmon-enhanced fluorescence, electroluminescence, and Raman scattering will be presented in different plasmonic nanocavities.<br/>The extreme subnanometric localization of light allows to understand ultraresolution in molecular vibrational spectroscopy, as achieved in intramolecule-resolved Surface-Enhanced Raman Spectroscopy. The small effective volumes associated to these special optical 'picocavities' are of particular interest in quantum nanooptics, as they provide particularly large values of the coupling strength of the plasmons with excitons of an emitter, or with mechanical vibrations of a molecule located in the cavity. This opportunity of large coupling can be exploited in molecular optomechanics of single molecules to obtain strong non-linear responses, enhancement of signals due to detuning, or to study Stokes/anti-Stokes correlations. Furthermore, electroluminescence of single molecules in STM configurations is found to resolve tautomer configurations of single molecules as well as their dynamics.<br/>Different quantum theoretical frameworks which merge techniques from condensed matter transport, quantum chemistry, and quantum nanooptics will be addressed to interpret the rich variety of spectral information obtained experimentally, resolved both in time and space.

Addressing atomically resolved molecular spectroscopy in plasmonic cavities

2019 Fall National Meeting

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