MECHANISM OF FLUX-LINE MOTION IN HIGH-TEMPERATURE SUPERCONDUCTORS

A model for vortex depinning and motion is presented, which takes into account the inhomogeneity of a real type-II superconducting material. The model is based upon a mechanism, in which the flux-line lattice is depinned by a synchronous shear around the vortices, which are too strongly pinned to be broken. In contrast to the classical flux-line shear model, variations in the vortex-vortex interactions are allowed. The applicability of this model is demonstrated by evaluating the real resistive data for the ceramic superconductor YBa2Cu3O7 in the mixed state. The simulated data agree very well with experimental observations. An Arrhenius-like temperature dependence of the resistance at the transition to the superconducting state is evaluated. The shape of the simulated voltage-current curves, the field and temperature dependence of the volume pinning force, and the position of the peak in the volume pinning force resemble experimental data. Furthermore, the presence of a reversible regime close to the transition to the normal state follows automatically from the model.