Segregated tunneling-percolation model for transport nonuniversality

C. Grimaldi; T. Maeder; P. Ryser; S. Straessler

doi:10.1103/physrevb.68.024207

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Segregated tunneling-percolation model for transport nonuniversality

C. Grimaldi·T. Maeder·P. Ryser·S. Straessler

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Abstract

We propose a theory of the origin of transport nonuniversality in disordered insulating-conducting compounds based on the interplay between microstructure and tunneling processes between metallic grains dispersed in the insulating host. We show that if the metallic phase is arranged in quasi-one dimensional chains of conducting grains, then the distribution function of the chain conductivities g has a power-law divergence for g -> 0 leading to nonuniversal values of the transport critical exponent t. We evaluate the critical exponent t by Monte Carlo calculations on a cubic lattice and show that our model can describe universal as well nonuniversal behavior of transport depending on the value of few microstructural parameters. Such segregated tunneling-percolation model can describe the microstructure of a quite vast class of materials known as thick-film resistors which display universal or nonuniversal values of t depending on the composition.

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C. Grimaldi, T. Maeder, P. Ryser, S. Straessler. 2003-06-26. Segregated tunneling-percolation model for transport nonuniversality. https://doi.org/10.1103/physrevb.68.024207

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