Nature of the Local Pairing of Charge Carriers in the Family of High-Temperature Superconductors Based on BaBiO3 (Brief Review)

A model of the local pairing of charge carriers in real space in a family of bismuthate high-temperature superconducting oxides based on X-ray absorption spectroscopy data using synchrotron and X-ray free-electron laser radiation is presented. The nature of the two band gaps and the insulator state of barium bismuthate BaBiO₃, the metallic state of the barium plumbate BaPbO₃, as well as the phase diagram and the appearance of superconductivity in lead- and potassium-doped BaBiO₃, has been explained. The possibility of implementing both phonon and electron pairing mechanisms is discussed.