Photoexcitation-induced magnetism in arrays of semiconductor nanoparticles with a strong excitonic oscillator strength

A type of magnetic metamaterial which exhibits strong magnetic activity within and below the optical region is presented. The metamaterial consists of semiconductor nanoparticles such as CuCl or Cu₂O particles. The magnetic activity is attributed to the strong oscillator strength stemming from the exciton absorption line. The magnetic permeability of the proposed metamaterial is calculated from the extended Maxwell-Garnett theory, and its validity is compared against ab initio layer multiple-scattering calculations. The proposed structure is a low-loss, subwavelength, isotropic magnetic metamaterial, and its response is robust against stacking and point disorder.