High-Temperature Superconductors. Overview

Abstract

High-temperature superconductors placed in the center of our research are the type-II superconductors. Therefore, their properties and superconductivity mechanisms are considered in more detail. The term type-II superconductors was first introduced by Abrikosov in his classical paper [4], where he assumed a detailed phenomenological theory of these materials’ behavior, based on the Ginzburg–Landau theory, and explained their magnetic properties. Initially, Abrikosov’s theory was greeted with certain skepticism: so much out of the ordinary was in its predictions. However, at the next development of physics of superconductors this theory obtained numerous experimental supports. Finally, several years later it was accepted in total, when it consequently explained the complex behavior of superconducting alloys and compounds, in particular the very high critical fields of some materials. As it has been noted for type-II superconductors, the energy of an interface between a normal and a superconducting region σ ns < 0. Total displacement of external field from superconductor does not lead to a state with the least energy, if the contribution of surface energy of the interface between two phases is significant. Therefore, in this case, the energetically favorable state is that at which superconductor of corresponding shape (any one, besides an infinitely long cylinder placed in a parallel magnetic field) is divided into great number of alternating superconducting and normal regions.