title: Unified understanding of superconductivity and Mott transition in alkali-doped fullerides from first principles.
abstract: Alkali-doped fullerides A 3C60 (A = K, Rb, Cs) are surprising materials where conventional phonon-mediated superconductivity and unconventional Mott physics meet, leading to a remarkable phase diagram as a function of volume per C60 molecule. We address these materials with a state-of-the-art calculation, where we construct a realistic low-energy model from first principles without using a priori information other than the crystal structure and solve it with an accurate many-body theory. Remarkably, our scheme comprehensively reproduces the experimental phase diagram including the low-spin Mott-insulating phase next to the superconducting phase. More remarkably, the critical temperatures T c's calculated from first principles quantitatively reproduce the experimental values. The driving force behind the surprising phase diagram of A 3C60 is a subtle competition between Hund's coupling and Jahn-Teller phonons, which leads to an effectively inverted Hund's coupling. Our results establish that the fullerides are the first members of a novel class of molecular superconductors in which the multiorbital electronic correlations and phonons cooperate to reach high T c s-wave superconductivity.
authors.affiliation: Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nomura
authors.affiliation: Center for Emergent Matter Science (CEMS), RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Sakai
authors.affiliation: International School for Advanced Studies (SISSA) and Consiglio Nazionale delle Ricerche-Istituto Officina dei Materiali (CNR-IOM) Democritos National Simulation Center, Via Bonomea 265, I-34136 Trieste, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Capone
authors.affiliation: Center for Emergent Matter Science (CEMS), RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan. ; Japan Science and Technology Agency (JST) ERATO Isobe Degenerate π-Integration Project, Advanced Institute for Materials Research (AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Arita
keywords: Dynamical Mean-Field Theory; Mott Transition; Strongly correlated materials; alkali-doped fullerides; density-functional theory; downfolding; electron-phonon interactions; first principles; unconventional superconductivity