Exotic s-wave superconductivity in alkali-doped fullerides

Yusuke Nomura, Shiro Sakai, Massimo Capone, Ryotaro Arita

Research output: Contribution to journalReview articlepeer-review

33 Citations (Scopus)

Abstract

Alkali-doped fullerides (A3C60 with A = K, Rb, Cs) show a surprising phase diagram, in which a high transition-temperature (Tc) 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-Tc 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. A driving force behind the exotic physics is unusual intramolecular interactions, characterized by the coexistence of a strongly repulsive Coulomb interaction and a small effectively negative exchange interaction. This is realized by a subtle energy balance between the coupling with the Jahn-Teller phonons and Hund's coupling within the C60 molecule. The unusual form of the interaction leads to a formation of pairs of up- and down-spin electrons on the molecules, which enables the s-wave pairing. The emergent superconductivity crucially relies on the presence of the Jahn-Teller phonons, but surprisingly benefits from the strong correlations because the correlations suppress the kinetic energy of the electrons and help the formation of the electron pairs, in agreement with previous model calculations. This confirms that the alkali-doped fullerides are a new type of unconventional superconductors, where the unusual synergy between the phonons and Coulomb interactions drives the high-Tc superconductivity.

Original languageEnglish
Article number153001
JournalJournal of Physics Condensed Matter
Volume28
Issue number15
DOIs
Publication statusPublished - 2016 Mar 14
Externally publishedYes

Keywords

  • alkali-doped fullerides
  • electron correlations
  • electron-phonon interactions
  • unconventional superconductivity

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

Fingerprint

Dive into the research topics of 'Exotic s-wave superconductivity in alkali-doped fullerides'. Together they form a unique fingerprint.

Cite this