Impurity pinning of sliding charge-density waves

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Abstract
A complete theoretical model is constructed to characterize the pinning of charge-density waves (CDW’s) to individual impurity sites. The model is based upon consistently incorporating the microscopic CDW-impurity interaction calculated by Tüttó and Zawadowski within the large-scale Ginzburg-Landau framework of Lee and Rice. This analysis shows that the local CDW pinning by impurities will always be strong for all realistic values of the scattering parameter. On the other hand, the large-scale average CDW phase away from the impurity sites will be weakly pinned over extended volumes containing a great many individual impurities, in nominally ‘‘pure’’ crystals. This interplay between ‘‘weak’’ and ‘‘strong’’ aspects of the impurity pinning is found to explain most features of the experimental phenomenology, including the remarkable behavior seen in the broadband 1/f-type noise spectrum above the depinning threshold.