Dynamics of metastable vortex states in weakly pinned superconductors: A phenomenological model

We present a phenomenological model for the vortex dynamics in the peak effect region of weakly pinned superconductors. We explain the history dependent dynamic response of the metastable vortex states subjected to a transport current and the hysteretic voltage-current characteristics observed in the vicinity of peak effect in weakly pinned superconductors. A strong variation in voltage current characteristics with the current sweep rate and the anomalous dependence of critical current density Jc on the magnetic field sweep rate have also been accounted for by this model. In weakly pinned superconductors, the competition between intervortex interaction and quenched disorder produces a sharp peak in the critical current density Jc just below the normal state boundary. This phenomenon, known as the peak effect[1] occurs when the vortex lattice passes from a state with a high degree of spatial order to an amorphous pinned state [2, 3]. The peak effect is often accompanied by a marked history dependence in Jc originating from different metastable configurations in which the vortex lattice could exist [4, 5, 6, 7, 8]. Another aspect of the metastability associated with the peak effect is seen in the history dependent dynamic response of the vortex lattice to a transport current[6]. It is presumed that this behavior is due to the rearrangement of the vortex lattice from one metastable configuration to another