Pinning of Vortices by a Cylindrical Defect in High-Temperature Superconductors

Abstract

The uniaxial anisotropic London equation is used to study the interaction between curved flux lines and a cylindrical defect inside a high-temperature superconductor. The distribution of the magnetic fields inside the high-temperature superconducting defect (a non-superconducting defect) and the superconducting medium (outside the defect) are exactly determined. The energy of the interaction between the curved flux lines and the defect, in terms of the flux line segment position, is obtained. The dependence of the free energy of the system on σ (the ratio between the penetration depths of the defect and the superconducting medium) and on the radius of the cylindrical defect are established. Moreover, the magnetic pinning force of the flux lines as well as the critical current density are determined. A good agreement with previous results is achieved.