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-insulat or composite, using a three-dimensional (d = 3) transfer-matrix algori thm. The real part of the effective conductivity, Reg(e) (omega), reve als (i) a Drude peak that appears only above the percolation threshold p(c); and (ii) a broad spectrum of surface-plasmon resonances whose l ower edge approaches zero frequency at p(c). Sufficiently near p(c), t he dielectric function is consistent with an expected scaling form pre viously verified in d = 2. The surface-plasmon spectrum resembles effe ctive-medium predictions except for a weak but persistent peak near 0. 4omega/omega(p).