We study the effect of impurities on the dynamics of charge-density waves. At low temperature it is a good approximation to restrict our attention to phase fluctuation only. The competition between the random impurity potential and the elastic energy for phase fluctuations leads us naturally to consider two limiting cases. In the strong pinning case the phase is pinned to each impurity site. The pinning frequency and the frequency-dependent conductivity can be calculated. In the weak pinning case the pinning mechanism is more subtle. We show that the system is pinned by effectively breaking up into domains. The domain size is estimated which in turn determines the pinning frequency. The frequency-dependent conductivity and the static dielectric constant are calculated.

• Received 30 March 1977

DOI:https://doi.org/10.1103/PhysRevB.17.535