Study of frequency band gaps in metal-dielectric composite materials

We theoretically investigate the dielectric properties of a granular metal-dielectric composite with negative effective permittivity capable of creating band gaps in a wide range of frequencies. When the effective permittivity of the composite is negative, the electromagnetic (EM) waves will be reflected. The results show that for a given volume fraction lower than the percolation threshold, the effective permittivity of the whole composite can be negative for a certain range of frequencies during which the EM waves are forbidden to propagate in the composite. Considering the different geometrical structure, we discuss the possibility of artificially preparing materials with negative permittivity that would create frequency band gaps. Furthermore, we also investigate a metal-dielectric system with non-spherical inclusion, which leads to multiple frequency gaps for the EM waves