Dynamics of transition from metastable disordered state to ordered state of vortex structure in 2H-NbSe 2 single crystals

Abstract

Current driven transition from a highly pinned metastable disordered phase (DP) to a more ordered equilibrium phase (EP) of vortex structure has been investigated in the peak effect regime of weakly pinned type-II superconductor 2H-NbSe 2. Critical current density ( J c) in DP shows a maximum at the onset of the peak effect (i.e. for applied field H = H on), where J c in the EP is observed to be minimum. Time needed for the transition depends exponentially on the transport current. A model to describe the kinetics of the transition is presented. Time dependence of voltage and the current dependence of relaxation time obtained from experiments are in good agreement with the model. Energy barrier ( U 0) characterizing the relaxation process extracted from the model also shows a peak at H on. Peaks in J c in the DP and U 0 have been qualitatively understood in terms of the interplay between elastic and pinning forces.