The dynamics of disordered systems and the motion of vortices in disordered type‐II superconductors

We develop a field theoretical method which permits us to study the dynamics of interacting particles in disordered systems. In particular, making use of a Hartree‐type approximation, we obtain a self‐consistent system of equations for disorder averaged quantities. The method is first applied to a single particle on a rough surface. Then, we calculate the current‐voltage (I‐V) characteristics of a type‐II superconductor in the flux flow regime. Finally, the structure of the steps is discussed which arise in the I‐V‐characteristics when a small ac field is superimposed on the constant voltage. These may serve as a probe for incipient melting of the vortex lattice.