EM characterization of Raspberry-like nanocluster metamaterials

This work investigates certain electromagnetic (EM) properties of metamaterials formed by densely arrayed nanoclusters of plasmonic nanoparticles. An approximate model based on the single dipole approach in conjunction with the multipole expansion of the scattered field is used to evaluate the electric and magnetic polarizabilities of the nanocluster. Then, the permittivity and permeability of the composite medium are estimated by the Maxwell Garnett homogenization model. Results obtained from these approximatations are compared with data from full-wave simulations, focusing on the characterization of the nanocluster resonant isotropic electric and magnetic responses to an incident wave field, and the possibility to realize an isotropic negative index materials at optical frequencies..