FLUX-LINE CUTTING IN TYPE-II SUPERCONDUCTORS

Experimental evidence for flux-line cutting in superconductors (intersection and cross-joining of singly quantized vortices) is briefly reviewed. The interaction energy between two straight vortices tilted at an angle α (≠ 0)is then shown to be finite in the London model, i.e., in the limit of vanishing core radius. Next, the activation energy and maximum interaction force are calculated for the vortices in an analytic approximation to the Ginzburg-Landau theory. Here two competing interactions determine the behavior. Electromagnetic repulsion (0 < α < π/2) varies as cos α and decays over distances scaled by the penetration depth λ, while core attraction is independent of α and varies over distances scaled by the coherence length ξ. The force is always repulsive at large flux-line separation (0 < α < π/2) and its maximum decreases rapidly as κ decreases, so that flux-line cutting isexpected to be more probable in low-κ materials. The calculations provide a basis for explaining longitudinal flux-flow resistance as well as some intriguing magnetization behavior in the same configuration. © 1979 Plenum Publishing Corporation.