Statistical and Scaling Properties of the ac conductivity in Thin Metal-Dielectric Composites

We study in this paper the scaling and statistical properties of the ac conductivity of thin metal-dielectric films in different regions of the loss in metallic components and particularly in the limit of vanishing loss. We model the system by a 2D RL − C network and calculate the effective conductivity by using a real space renormalization group method. It is found that the real conductivity strongly fluctuates for very small losses. The correlation length, which seems to be equivalent to the localization length, diverges for vanishing losses confirming our previous results for the decay of the real conductivity with the loss. We found also that the distribution of the real conductivity becomes log-normal below a certain critical loss Rc which is size dependent for finite systems. For infinite systems this critical loss vanishes and corresponds to the phase transition between localized modes for finite losses and the extended ones at zero loss.