title: 'True' bosonic coupling strength in strongly correlated superconductors.
abstract: Clarifying the coupling between electrons and bosonic excitations (phonons or magnetic fluctuations) that mediate the formation of Cooper pairs is pivotal to understand superconductivity. Such coupling effects are contained in the electron self-energy, which is experimentally accessible via angle-resolved photoemission spectroscopy (ARPES). However, in unconventional superconductors, identifying the nature of the electron-boson coupling remains elusive partly because of the significant band renormalization due to electron correlation. Until now, to quantify the electron-boson coupling, the self-energy is most often determined by assuming a phenomenological 'bare' band. Here, we demonstrate that the conventional procedure underestimates the electron-boson coupling depending on the electron-electron coupling, even if the self-energy appears to be self-consistent via the Kramers-Kronig relation. Our refined method explains well the electron-boson and electron-electron coupling strength in ruthenate superconductor Sr2RuO4, calling for a critical revision of the bosonic coupling strength from ARPES self-energy in strongly correlated electron systems.
authors.affiliation: Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan. h-iwasawa@hiroshima-u.ac.jp
authors.forename: Hideaki
authors.initials: H
authors.lastname: Iwasawa
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Izumi
authors.initials: I
authors.lastname: Hase
authors.forename: Kenya
authors.initials: K
authors.lastname: Shimada
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Namatame
authors.forename: Masaki
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Aiura
mesh_terms: D055598:Chemical Phenomena; D003300:Copper / Q000737:chemistry*; D004553:Electric Conductivity; D004583:Electrons; D060739:Phonons; D056951:Photoelectron Spectroscopy; D017975:Ruthenium Compounds / Q000737:chemistry*; D013324:Strontium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D017975:Ruthenium Compounds; D003300:Copper; C027646:ruthenium tetraoxide; D013324:Strontium