Theoretical investigation on the optical response of the artificial magnetic-plasmonic nanoclusters

Bottom-up nanofabrication, organizing colloidal nanoparticles into ordered clusters with structural and functional complexity, provides an alternative to yield nanometric smart structures unachievable in traditional top-down approaches. Those remarkable structures assembled of colloidal nanoparticles possessing optical properties feature exotic optical responses under the illumination of incident light, showing highly dependent on the particle separation, composition, and arrangement. Here, the nanoscale electromagnetic coupling in magnetic-plasmonic nanoparticle clusters is analyzed by using a 3D full-wave computational model, and the mechanism of the resonances in a split-ring resonator out of magnetic-plasmonic nanoparticle building blocks is also illustrated. In particular, once assembling those artificial molecules (split-ring resonator) into secondary metamaterial superstructures, such as split-ring resonator dimer and Y-shaped structures, a series of exotic optical responses are presented due to the greatly enhanced near-field coupling of nanoparticles and the generation of antiparallel ring currents in the asymmetrical superstructure, exhibiting flexible sensitivity to the changes of the surrounding environment. Besides, the H-shaped arrangement exhibits high sensitivity with Q = 50.5 at lambda = 2.02 mu m. Our finding provides a platform for yielding complex structures with flexible tunability of the optical response through arranging those assembled artificial molecules into complex secondary structures, allowing for the development of smart sensing devices.