Near-Field Localization of Single Au Cubes: A Group Theory Description

Abstract : A simple group theory approach is proposed to predict the charge distribution of low order localized surface plasmon resonances (LSPRs) of finite metallic particles of basic geometries. As an illustration, the case of randomly oriented Au colloidal particles of cubic C$_{4v}$ symmetry excited at dipolar resonance is presented. The symmetry approach is confirmed by numerical simulations carried out by the $boundary$ $element$ $method$. Experimental validation is achieved by high-resolution subwavelength near-field mapping conducted by $photoemission$ $electron$ $microscopy$.