Nonlinear Conductivity and Noise due to Charge-Density-Wave Depinning in Nb${\mathrm{Se}}_3$

A simple model for the depinning and dynamics of a sliding charge-density wave is presented. The model consists of viscously damped motion in a periodic potential and accounts for the main features of the nonlinear conductivity, noise, and ac-dc coupling in the charge-density-wave state of Nb${\mathrm{Se}}_3$ at low temperature. Comparison with experimental data suggests that the depinning process is associated with the displacement of the charge-density wave by approximately one period $\lambda$.