HYSTERESIS AND INSTABILITY OF A DRIVEN INTERFACE IN A PERIODIC POTENTIAL

We discuss the inertial motion of an interface or linear defect driven in a periodic potential. When the interface modes are underdamped, a moving interface becomes unstable against spontaneous roughening at lo w velocity. We predict that this instability can be realized (for exam ple) at low temperatures for dislocations in Cu, leading to possibly p eculiar mechanical properties in the unstable regime. In the inertial regime the surface of a He-4 crystal might exhibit a linear relationsh ip between growth velocity and external driving force, once it has bee n set into motion.