Superconductivity in Fullerides

TL;DR

This paper reviews experimental and theoretical research on superconductivity in fullerides, focusing on electron-phonon interactions, Coulomb effects, and theoretical models, highlighting why A3C60 compounds are superconductors despite strong Coulomb repulsion.

Contribution

It provides a comprehensive comparison of experimental coupling constants with theoretical calculations and discusses the electronic mechanisms behind superconductivity in fullerides.

Findings

A3C60 compounds are not Mott-Hubbard insulators despite large Coulomb interactions.

Calculated electron-phonon coupling constants align with experimental data.

Estimates of Coulomb pseudopotential μ* inform understanding of superconductivity mechanisms.

Abstract

Experimental studies of superconductivity 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 the A_3 C_60 are not Mott-Hubbard insulators, in spite of the large Coulomb interaction. Estimates of the Coulomb pseudopotential $\mu^*$, 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.