title: Anomalous quasiparticle lifetime and strong electron-phonon coupling in graphite.
abstract: We have performed ultrahigh-resolution angle-resolved photoemission spectroscopy on high-quality single crystals of graphite to elucidate the character of low-energy excitations. We found evidence for a well-defined quasiparticle (QP) peak in the close vicinity of the Fermi level comparable to the nodal QP in high-T(c) cuprates, together with the mass renormalization of the band at an extremely narrow momentum region around the K(H) point. Analysis of the QP lifetime demonstrates the presence of strong electron-phonon coupling and linear energy dependence of the QP scattering rate indicative of a marked deviation from the conventional Fermi-liquid theory.
authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sugawara
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Souma
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Suematsu