Field-dependent critical current in type-II superconducting strips: Combined effect of bulk pinning and geometrical edge barrier

Recent theoretical and experimental research on low-bulk-pinning superconducting strips has revealed striking domelike magnetic-field distributions due to geometrical edge barriers. The observed magnetic-flux profiles differ strongly from those in strips in which bulk pinning is dominant. In this paper we theoretically describe the current and field distributions of a superconducting strip under the combined influence of both a geometrical edge barrier and bulk pinning at the strip's critical current I-c, where a longitudinal voltage first appears. We calculate I-c and find its dependence upon a perpendicular applied magnetic field H-a. The behavior is governed by a parameter p, defined as the ratio of the bulk-pinning critical current I-p to the geometrical-barrier critical current I-s0. We find that when p>2/pi and I-p is field independent, I-c vs H-a exhibits a plateau for small H-a, followed by the dependence I-c-I(p)proportional toH(a)(-1) in higher magnetic fields.