NONLINEAR CONDUCTIVITY OF CHARGE-DENSITY-WAVE SYSTEMS

We consider the problem of sliding motion of a charge-density-wave sub ject to static disorder within an elastic medium model. Starting with a field-theoretical formulation. which allows exact disorder averaging , we propose a self-consistent approximation scheme to obtain results beyond the standard large-velocity expansion. Explicit calculations ar e carried out in three spatial dimensions. For the conductivity. we fi nd a strong-coupling regime at electrical fields just above the pinnin g threshold. Phase and velocity correlation functions scale differentl y from the high-field regime, and static phase correlations converge t o the pinned-phase behaviour. The sliding charge-density-wave is accom panied by narrow-band noise.