Anomalous spectral shifts in extreme plasmonic nano-cavities

Abstract

Nanoplasmonics have the ability to confine light in sub-wavelength cavities, with recent nano-fabrication developments allowing for the realization of nanometer and sub-nanometer plasmonic cavities. We show that for such extremely small nano-cavities, the correlation between the field enhancement resonance and the radiative (far-field) resonance breaks down. This dissociation dominated the excitation and interference of higher-order modes in these nano-cavities. We discuss and demonstrate the impact of this anomalous spectral behaviour for the strong coupling of quantum emitters with plasmonic nano-cavities, where it is imperative to have nanosized cavities.