Non-linear transport in disordered carbon-black/polymer composites

In disordered systems, the dependence of the DC conductivity on the electric field E increases when the temperature is lowered. We studied the non-ohmic conductivity sigma(E) of a series of carbon-black/polymer composites as a function of temperature T and concentration p. The low-temperature results indicate that the strength of E affects the path along which conduction proceeds through the materials. The new characteristic length scale is a few times larger than found in the zero electric-field limit.