Scaling theory applied to far-infrared absorption by metal-insulator composite materials

Dynamic scaling theory is used to obtain expressions for the far-infrared absorption coefficient {α} of metal-insulator granular composite materials near the dc percolation threshold pc in the quasistatic limit. An anomalous frequency dependence is predicted near pc for 50-{}-radius Au particles. The frequency dependence of {α} obtained from an analysis of published data on Au blacks is inconsistent with the scaling theory for Drude Au particles in the three-dimensional limit, and the theoretical estimate of the magnitude of {α} at {ω} ̃ \~{}{}=100 cm^-1 is a factor of 7 too large.