Magnetic self-field entry into a current-carrying type-II superconductor. III. General criterion of penetration for an external field of arbitrary direction

Abstract

The first magnetic-flux penetration into a current-carrying cylindrical type-II superconductor subjected to an external magnetic field is considered in the frame of the London approximation. The lower transverse critical field as well as critical field of the first vortex nucleation at the surface are evaluated on the basis of an exact solution for a vortex of arbitrary flat configuration. Taken together with the previous consideration of the parallel magnetic-field penetration in a current-carrying superconductor [Phys. Rev. B 49, 6950 (1994) and B 51, 3686 (1995)] the above results allow us to formulate the general criterium for the first flux entry in the current-carrying samples of arbitrary transverse size subjected to an external field of arbitrary direction.