Sliding Conductivity of Charge-Density Waves

A classical model of charge-density wave motion at large velocities is used to describe the nonlinear response of the charge-density wave in fields well above the threshold. The charge-density wave is regarded as a charged, deformable medium and its interaction with pinning centers is treated in perturbation theory. The results fit the available high-field data on ${\mathrm{NbSe}}_3$ well. The observed interference effects between a large dc field and an ac field are also explained.