Bipolarons and superconductivity

Abstract

Formation of real-space localised pairs of electrons as observed in many solids are shown to be phonon mediated and resembles in this respect to the mechanism involved in B. C.S. pairing of superconductivity. Profound analogies exist between these two kinds of pairs and will be explored. The localised pair of electrons in a singlet state is the ground state beyond a critical value of the electron-phonon coupling constant. Treating the two-electron scattering problem, one can obtain the expected behavior of the chemical potential in the two limits. Several examples will be given of real-space pairing and of anomalous superconductivity in some systems.