Low field penetration and intrinsic critical currents in layered superconductors

Trapping of flux line cores between weakly coupled superconducting layers is considered. An estimate of the resulting high intrinsic critical current is given for field and current both parallel to the layers. The first flux penetration is studied as a function of the field direction. Each flux line takes the shape of a Sine-Gordon soliton lattice and encounters a lock-in transition towards the layers at a critical orientation