Closely packed metallic nanocuboid dimer allowing plasmomechanical strong coupling

Abstract

By connecting the optical and mechanical degrees of freedom, an optomechanical system can provide schemes for coherent control over the quantum states once entering the strong coupling regime. Well known as a unique substitution of conventional microcavities allowing operating in the deep subwavelength scale, plasmonic nanocavities usually suffer from pronounced dissipative loss that hinders the realization of strong coupling in the weak excitation limit. Here we theoretically predict that weak-excitation plasmomechanical strong coupling can be realized in a system consisting of two cuboid-shaped metal nanoparticles. It takes full advantage of a recorded low-loss nanocavity plasmon which is simultaneously highly sensitive to the interparticle distance and imposes an intense optical binding force between the two cuboids. The theoretical minimal number of plasmon quanta required by strong coupling is 441 for silver at optical frequency and 25 for graphene at near infrared. This plasmomechanical prototype could potentially offer a nanoscale testbed for quantum experiments in strong coupling regimes and further enrich the toolbox for sensing and precise measurements in molecular scale.