Yusuke Nomura, Shiro Sakai, Massimo Capone and Ryotaro Arita

Alkali-doped fullerides (A₃C₆₀ with A= K, Rb, Cs) show a surprising phase diagram, in which a high transition-temperature (T_c) s-wave superconducting state emerges next to a Mott insulating phase as a function of the lattice spacing. This is in contrast with the common belief that Mott physics and phonon-driven s-wave superconductivity are incompatible, raising a fundamental question on the mechanism of the high-T_c superconductivity.

This article reviews recent ab initio calculations, which have succeeded in reproducing comprehensively the experimental phase diagram with high accuracy and elucidated an unusual cooperation between the electron-phonon coupling and the electron-electron interactions leading to Mott localization to realize an unconventional s-wave superconductivity in the alkali-doped fullerides.