Theory of measurements of d.c. and a.c. resistivity in anisotropic superconductors in tilted magnetic fields

Abstract

The vortex dynamics of uniaxial anisotropic superconductors with arbitrary angles between the magnetic field, the applied current and the anisotropy axis is theoretically studied, by focusing on the models for electrical transport experiments in the linear regime. The vortex parameters, such as the viscous drag, the vortex mobility and the pinning constant (in the weak point pinning regime), together with the vortex motion resistivity, are derived in tensor form by considering the very different free flux flow and pinned Campbell regimes. The results are extended to high frequency regimes where additional effects like thermal depinning/creep take place. The applicability to the various tensor quantities of the well-known scaling laws for the angular dependence on the field orientation is commented, illustrating when and with which cautions the scaling approach can be used to discriminate between intrinsic and extrinsic effects. It is shown that the experiments do not generally yield the intrinsic values of the vortex parameters and vortex resistivities. Explicit expressions relating measured and intrinsic quantities are given and their use exemplified in data analyses of angular measurements.