Apparent nonuniversality in finite segregated tunneling–percolation models

We investigate the tunneling–percolation mechanism of DC transport nonuniversality for conducting particles of diameter φ placed in series within the bonds of length L of a regular lattice model. When L/φ→∞ the resulting bond conductance distribution function has a power-law divergence as g→0, leading to nonuniversal values of the transport exponent. Instead, finite values of L/φ prevent the onset of nonuniversality. However, depending on the model parameters, universality can be restricted to a very narrow region around the critical percolation threshold so that, for all practical purposes, DC transport continues to behave as nonuniversal. We argue that experimentally such behavior may be indistinguishable from that of a truly intrinsic nonuniversal system.