Diffusion and dynamical randomness of the flux flow state in high temperature superconductors

Abstract

In strongly layered superconductors, the dynamical system of vortex lattice is a disordered state with large energy of the vortex bundle for small driving currents. We provide an evidence that broadening of the resistive transitions in HTSC measured under magnetic field is due to random diffusion and fast relaxational hopping of flux lines between different metastable configurations. A model is presented in which the dynamics of the two-dimensional vortex lattice are characterized by a diffusive transfer rather than distinct movements of the vortices. The predictions of the model are consistent with large scale numerical simulation on two-dimensional vortex lattice using molecular dynamics' methods. In addition, excellent agreements were established between the model calculations and the measured resistive transitions in twined (YBaCuO) single crystal high temperature superconductors (HTSC).