Vortex dynamics in disordered type-II superconductors.

We develop a field theoretical method which permits us to study the dynamics of vortices in disordered superconductors. In particular, we obtain a self-consistent system of equations for disorder averaged quantities. Making use of a Hartree-type approximation, we calculate the current-voltage (I-V) characteristics in the flux flow regime. In order to probe incipient melting of the vortex lattice we propose an experiment where interference steps in the I-V characteristics of a superconducting film are observed, which arise when a small ac field is superimposed on the constant voltage.