Dynamic instability of dislocations due to nucleation of a new phase

Dislocation lines in a crystal close to a bulk phase transition can be coated by nuclei of a new phase which for a moving dislocation gives rise to a viscous friction force. In some range of the material parameters this force leads to a dynamic instability of the defect line, resulting from an intricate interplay between the shape fluctuations of the defect and the amplitude fluctuations of the nucleus. The instability shows up in the linear response of the dislocation to a periodic change of the driving force and in the structure factor of the order-parameter fluctuations of the nucleus.