Percolation-localization crossover and depression of the superconducting transition temperature in films of metal-insulator mixtures.

Recent experiments on the conductivity and the onset of superconductivity in thin metal-insulator-mixture films are interpreted in terms of an ansatz which provides a criterion for the crossover between percolation and localization. In agreement with experiment, this ansatz predicts that percolation dominates in large-grain structures and localization in amorphous ones, providing a unified view of the apparently disparate results on different types of metal-insulator mixtures.