Non-Gaussian resistance noise near electrical breakdown in granular materials

The distribution oif resistance fluctuations of conducting thin films with granular structure near the electrical breakdown is studied by numerical simulations. The film is modeled as a resistor netowkr ina steady state determined by the competition between two biased processes, breaking and recovery. Systems of different sizes and with different levels of internal disorder are considered. Sharp deviations from the Gaussian distribution are found near the breakdown and the effect increases with the degree of internal disorder. We show that in general this non-Gaussian behaviour is related to the finite size of the system and vanishes in the large size limit. Neverthless, near the critical point of the conductor-insulator transition, deviations from the Gaussian shape persist when the size is increased an the distribution of resistance fluctuations is wel fitted by the universal Bramwell-Holdsworth-Pintor distribution.