Materials (II)

This chapter describes the properties of a number of interesting superconducting materials. The study of phonon-mediated superconductors, such as A-15 materials and MgB2, flourished after the discovery of the high-Tc hydrides. At present, this family displays, under high pressure, record values of Tc close to room temperature. Other interesting systems, such as pnictides, heavy fermions, and ruthenates, with their peculiar interplay of superconductivity and magnetism, are also described. Fe-based superconductors, which were recently discovered, have relatively high Tc at ambient pressure. They display a two-gap energy spectrum. Pairing in intercalated nitrides is mainly provided by acoustic plasmons. Tungsten oxides represent a new family of oxides containing elements other than copper; they form filamentary structures. A special class is formed by topological superconductors; usually their properties are caused by odd-parity pairing. The presence of the states inside of the energy gap make these superconductors similar to topological insulators.