Optical properties of a disordered metallic film: local vs. collective phenomena

We apply the dual-varibles approach to the problem of the optical response of an disordered film of metal particles with dipole-dipole interaction. Long range dipole-dipole interaction makes the effect of spatial correlations significant, so that dual-variables technique provides a desirable improvement of the coherent-potential results. It is shown that the effect of nonlocality is more pronounced for a medium-range concentration of the particles. The result is compared with the non-local cluster approach. It is shown that short-range correlations accounted in the cluster method reveal themselves in the spectral properties of the response, whereas long-range phenomena kept in the dual technique are more pronounced in the k-dependence of the Green's function.