The role of electron-vibron interaction and local pairing in conductivity and superconductivity of alkali-doped fullerides. The route to a room-temperature superconductor

Abstract

We investigate the competition between the electron-vibron interaction (interaction with the Jahn-Teller phonons) and the Coulomb repulsion in a system with local pairing of electrons on the triply degenerate lowest unoccupied molecular orbital (LUMO). The electron-vibron interaction radically changes conductivity and magnetic properties of alkali-doped fullerides AnC60, which should be antiferromagnetic Mott insulators: we have found that materials with n=1,2 and A=K,Rb are conductors but not superconductors; n=3 and A=K,Rb are conductors (superconductors at low temperatures), but with A=Cs are Mott insulators at normal pressure; n=2,4 are nonmagnetic Mott insulators. We have shown that superconductivity, conductivity and insulation of these materials have common nature. Based on the alkali-doped fullerides we propose a hypothetical material with a significantly higher critical temperature using the model of superconductivity with the external pair potential formulated in a work K.V. Grigorishin Phys. Lett. A 381 3089 (2017).