Flux pinning and peak effects in single crystalline 2H-NbSe 2

Abstract

In this paper we present the field dependence of the flux line pinning force of very thin (d=2-15.5 μm) single crystals of the anisotropic low temperature superconductor 2H-NbSe 2 , where the field is normal to the superconducting Nb-layers. Below B c0 0.8 B c2 the pinning force can well be described by the two-dimensional collective pinning (CP) theory. Between B c0 and B c2 a peak effect is observed which we interpret as a transition from two to three-dimensional disorder in the flux line lattice. Comparison of the crossover conditions with the criterion set by the CP- theory reveals for the first time that the tilt niodulus for an anisotropic superconductor is largely reduced in a way predicted by a recently obtained theoretical expression.