Optical properties of a disordered metallic film: local versus collective phenomena

We apply the dual-variable approach to the problem of the optical response of a disordered film of metal particles with dipole-dipole interaction. Long-range dipole-dipole interaction makes the effect of spatial correlations significant, so that the dual-variable technique provides a desirable improvement of the coherent-potential results. It is shown that the effect of non-locality is more pronounced for a medium-range concentration of particles. The result is compared with the non-local cluster approach. The short-range correlations accounted for 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.