Negative curvature dependent plasmonic coupling and local field enhancement of crescent silver nanostructure

The plasmonic spectra and local field enhancement properties of the silver nanocrescent with fixed maximum thickness are theoretically studied using the discrete dipole approximation calculation. Both the particle plasmon mode and tip-cavity plasmonic coupling of the nanocrescent could be fine tuned by controlling the negative curvature of the nanocavity. The plasmonic conversion between particle plasmon of the silver tip and symmetric plasmon hybridization of the silver shell could be switched by changing the open and close state of the nanocavity. The intensity of intra-particle plasmonic coupling between tip and cavity resonance and the corresponding local field enhancement could also be tuned by the cavity radius. This study indicates that the metal surface with changing negative curvature takes great effect on the surface charge distribution of the metallic nanostructure and then controls the plasmon coupling and local field enhancement.