Macroscopic Quantum System, Highly Correlated Electron State, and High-Temperature Superconductivity in Iron Pnictides

Abstract

The qualitative model of the high-temperature superconductivity suggested earlier for cuprates and based on the idea that the superconductivity is associated with delocalized π bonding between ions is not only confirmed by experimental data on iron pnictides but is also improved. It is shown that the FeAs layer state is similar to that of a macroscopic quantum system characterized by a sandwich-type charge distribution in which negatively charged planes are two-dimensional electron crystals of pairs and positively charged planes are formed by positively charged ions. Superconductivity in such a system is accomplished by a two-dimensional Wigner crystal of bosons condensed into one and the same state. The crystal occupies a middle position with respect to charged planes in the sandwich structure, which leads to mutual compensation of all its interactions with all charged planes. The model can prove useful for development of the theory of superconductivity taking into consideration the highly correlated state of all valence electrons that manifests itself in formation of electron crystals with strong Coulomb interactions between them.