Variable-range hopping within a fluctuating potential landscape

The effect of temporal and spatial potential-energy fluctuations on low-temperature dark de conductivity in disordered materials is considered. Analytical models are formulated to treat the variable-range hopping in a disordered system of localized states whose energies are subjected to 1/f temporal fluctuations. Long-range spatial potential fluctuations are described as a random distribution of intrinsic electric field, Temporal 1/f fluctuations are assumed either to be independent of carrier hopping or to be caused by the latter process. Both spatial and independent 1/f temporal fluctuations are shown to yield temperature dependences of the conductivity much weaker than those predicted by the Mott law, Self-sustaining 1/f temporal fluctuations caused by the carrier random walk lead to the crossover from Mott's T-1/4 to T-1/3 dependence with increasing temperature.