Angular Dependence of the Upper Critical Field of Superconducting Superlattices

Abstract

Using Takahashi-Tachiki’s theory and a perturbation method, we qualitatively show that dH_c2(θ)⁄dθ does not vanish at θ=0, in agreement with the experimental results. Here, H_c2(θ) is the upper critical field of the superconducting superlattices and θ is the angle of the direction of the magnetic field measured from the layer plane of the superlattices.