Defects, order, and hysteresis in driven charge-density waves

We model driven two-dimensional charge-density waves in random media via a modified Swift-Hohenberg equation, which includes both amplitude and phase fluctuations of the condensate. As the driving force is increased, the defe ct density first increases and then decreases. Furthermore, we find switchi ng phenomena, due to the formation of channels of dislocations. These resul ts are in qualitative accord with recent dynamical x-ray scattering experim ents by Ringland er al. [Phys. Rev. Lett. 82, 1923 (1999)] and transport ex periments by Lemay et al. [Phys. Rev. Lett. 83, 7793 (1999)].