We investigate the design of artificial (negative) permeability and backward-wave metamaterials in the terahertz range from arrays of dielectric TiO2 spheres embedded in a host medium. Artificial magnetism arising from arrays of such spheres, is studied both analytically and numerically. We also show that, due to interparticle coupling, bidisperse arrays of real material spheres in the terahertz are unable to provide double-negativity. However, we find that a new physical mechanism takes over and that there are bands of backward waves (despite a positive refractive index) that appear both in bidisperse and monodisperse arrays.
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