Superconductivity in fullerides

TLDR

Fullerides’ superconductivity has been explored experimentally and theoretically, with particular emphasis on intramolecular electron‑phonon coupling. The study investigates why A₃C₆₀ fullerides are not Mott‑Hubbard insulators despite strong Coulomb interactions. The authors compare calculated electron‑phonon coupling constants with experimental values, review Coulomb pseudopotential estimates and alternative electronic mechanisms, and compute superconducting properties using Migdal‑Eliashberg theory while exploring extensions beyond it.

Abstract

Experimental studies of the superconductive properties of fullerides are briefly reviewed. Theoretical calculations of the electron-phonon coupling, in particular for the intramolecular phonons, are discussed extensively. The calculations are compared with coupling constants deduced from a number of different experimental techniques. It is discussed why ${\mathrm{A}}_{3}$${\mathrm{C}}_{60}$ are not Mott-Hubbard insulators, in spite of the large Coulomb interaction. Estimates of the Coulomb pseudopotential ${\mathrm{\ensuremath{\mu}}}^{\mathrm{*}}$, describing the effect of the Coulomb repulsion on the superconductivity, as well as possible electronic mechanisms for the superconductivity, are reviewed. The calculation of various properties within the Migdal-Eliashberg theory and attempts to go beyond this theory are described.