Sliding charge-density waves. I. dc properties

Abstract

A classical model of a sliding charge-density wave (CDW) is extended to treat the electrostatic interaction of the CDW with itself, conduction electrons, and the host lattice, as well as with defects. If the CDW is commensurate and the lattice sufficiently coherent, the interaction with the lattice produces, at large voltages, a leading-order nonlinear current of the form $\ensuremath{\Delta}I\ensuremath{\propto}\ensuremath{-}{V}^{\ensuremath{-}1}$, which contrasts with $\ensuremath{\Delta}I\ensuremath{\propto}\ensuremath{-}{V}^{\frac{1}{2}}$ due to defects. The effect of a large decrease in the normal conductivity is studied and the defect-contributed $\ensuremath{\Delta}I$ is predicted to be strongly enhanced with decreasing temperature in Ta${\mathrm{S}}_{3}$. Interference effects in the commensurate and incommensurate cases are also shown to differ in both detailed shape and temperature dependence. Transport measurements may, therefore, be able to determine whether the CDW's in Ta${\mathrm{S}}_{3}$ and Nb${\mathrm{S}}_{3}$ are commensurate or incommensurate.