SCALING BEHAVIOR AND SURFACE-PLASMON RESONANCES IN A MODEL 3-DIMENSIONAL METAL-INSULATOR COMPOSITE

we calculate the ac dielectric function of a model Drude metal-insulator composite, using a three-dimensional (d = 3) transfer-matrix algorithm. The real part of the effective conductivity, Reg(e) (omega), reveals (i) a Drude peak that appears only above the percolation threshold p(c); and (ii) a broad spectrum of surface-plasmon resonances whose lower edge approaches zero frequency at p(c). Sufficiently near p(c), the dielectric function is consistent with an expected scaling form previously verified in d = 2. The surface-plasmon spectrum resembles effective-medium predictions except for a weak but persistent peak near 0.4omega/omega(p).