Anisotropic Superconductors: Fundamentals of Vortices in Layered Superconductors

Abstract

Some fundamentals of the magnetic structure in anisotropic superconductors are presented. The approach focuses on the vortex structure in layered superconductors, the most important example being the high-Tc cuprates. The GinzburgLandau theory is discussed, as well as its extensions to include anisotropy via an anisotropic effective mass tensor. The Lawrence-Doniach theory is introduced, and it is used to show that a vortex parallel to the layers has a Josephson core confined to the interlayer junction. Two-dimensional (2D) pancake vortices are discussed, and the fields and currents generated by them are presented. The Josephson coupling energy between 2D pancake vortices in adjacent layers is estimated. Some basics of flux pinning in the layered superconductors are examined. Finally, an explanation is given of why the activation energy is much larger than the single-pancake pinning energy in strongly coupled superconductors but is approximately equal to the single-pancake pinning energy in weakly coupled superconductors.