Nonlinear conduction and anomalous susceptibility of sliding electronic crystals: Charge and spin density waves.

Metastable plastic deformations of sliding electronic crystals determine their low frequency dielectric susceptibility epsilon(T, omega), long time relaxation and nonlinear I - V characteristics. We present a theory of plastic deformations due to the pinning induced dislocation loops which originate the local metastable state. Within the same model we describe the two remarkable features which became commonly observed in Charge and Spin Density Waves (DW). There are both the anomalous peak of epsilon(T, omega = const) and the characteristic I - V curve with second threshold field in sliding regime. Namely the features of epsilon(T) result from a competition of the local relaxation with the collective pinning effected by freezing of the Coulomb screening. The upper critical field in I - V curves is reached when the shortest life time configurations are accessed by the fast moving DW.