Impurity pinning of discommensurations in charge-density waves

Abstract

The position of a discommensuration (DC) in a charge-density-wave state is pinned by impurities. This pinning gives rise to a barrier to the motion of a DC. If the pinning is weak the radius of curvature of the fluctuations in the position of the DC is large. Impurity pinning will enhance the hysteresis of a phase transition which requires the motion of DC, e.g., the stripehexagonal phase transition. As the temperature is raised, thermal fluctuations of the DC can cause a depinning transition of an isolated DC---a transition akin to the roughening transition of an interface. Depinning can also be achieved by external perturbations such as electric fields or inhomogeneous stresses.