The role of electron-vibron interaction and local pairing in conductivity and superconductivity of alkali-doped fullerides

Abstract

We investigate the competition between the electron-vibron interaction (interaction with the Jahn-Teller phonons) and the Coulomb repulsion in a system with the local pairing of electrons on the 3-fold degenerate lowest unoccupied molecular orbital (LUMO). The el.-vib. interaction and the local pairing radically change conductivity and magnetic properties of alkali-doped fullerides ${\text{A}}_n{\text{C}}_{60}$, which would have to be antiferromagnetic Mott insulators: we have shown that materials with $n=1,5$ and $\text{A}=\text{K},\text{Rb}$ are conductors but not superconductors; $n=3$ and $\text{A}=\text{K},\text{Rb}$ are conductors and superconductors at low temperatures, but with $\text{A}=\text{Cs}$ they are Mott-Jahn-Teller insulators at normal pressure; $n=2,4$ are nonmagnetic Mott insulators. Thus superconductivity, conductivity and insulation of these materials have common nature. Using this approach we obtain the phase diagram of ${\text{A}}_3{\text{C}}_{60}$ analytically, which is the result of interplay between the local pairing, the el.-vib. interaction, Coulomb correlations, and formation of small radius polarons.

23 pages, 9 figures. arXiv admin note: text overlap with arXiv:1610.08233

References in corpus (4)

• Strong electronic correlations from Hund's coupling
• NMR study of the Mott transitions to superconductivity in the two Cs_3C_60 phases
• Superconductivity in the two-band Hubbard model
• Jahn-Teller effect versus Hund's rule coupling in C60N-

Cited by in corpus (2)

• Theoretical Phase diagram of unconventional alkali-doped fullerides
• Merohedral disorder and impurity impacts on superconductivity of fullerenes