Resistance-current curves of high pinning superconductors

The lack of universal phenomenological approaches to calculation of the spatiotemporal distributions of vector fields in superconducting materials with high anisotropic pinning hinders the analysis of accumulated empirical data. The development of such phenomenology is impeded by the tradition of inadequate description of the transition characteristics of superconductors. Based on a detailed investigation of the current-dependent transitions in commercial niobium-titanium wire, it has been found that, in contrast to the commonly accepted approach, the transition characteristics are conveniently described as the dependences of the resistance on the current, by analogy with the dependences on the temperature and magnetic field. Investigations in the range of magnetic fields from 0 to Bc2 showed that it is the resistance that exhibits exponential variation with the field. The values of resistances determined by extrapolation of the transition curves to a zero current obey the exponential dependence on the magnetic field. The experimental results are consistent with predictions of the statistical model explaining the shape of the transition characteristic as determined by the bulk inhomogeneity of the superconductor.