title: Evidence for ubiquitous strong electron-phonon coupling in high-temperature superconductors.
abstract: Coupling between electrons and phonons (lattice vibrations) drives the formation of the electron pairs responsible for conventional superconductivity. The lack of direct evidence for electron-phonon coupling in the electron dynamics of the high-transition-temperature superconductors has driven an intensive search for an alternative mechanism. A coupling of an electron with a phonon would result in an abrupt change of its velocity and scattering rate near the phonon energy. Here we use angle-resolved photoemission spectroscopy to probe electron dynamics-velocity and scattering rate-for three different families of copper oxide superconductors. We see in all of these materials an abrupt change of electron velocity at 50-80 meV, which we cannot explain by any known process other than to invoke coupling with the phonons associated with the movement of the oxygen atoms. This suggests that electron-phonon coupling strongly influences the electron dynamics in the high-temperature superconductors, and must therefore be included in any microscopic theory of superconductivity.
authors.affiliation: Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lanzara
authors.forename: P V
authors.initials: PV
authors.lastname: Bogdanov
authors.forename: X J
authors.initials: XJ
authors.lastname: Zhou
authors.forename: S A
authors.initials: SA
authors.lastname: Kellar
authors.forename: D L
authors.initials: DL
authors.lastname: Feng
authors.forename: E D
authors.initials: ED
authors.lastname: Lu
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
authors.forename: H
authors.initials: H
authors.lastname: Eisaki
authors.forename: A
authors.initials: A
authors.lastname: Fujimori
authors.forename: K
authors.initials: K
authors.lastname: Kishio
authors.forename: J I
authors.initials: JI
authors.lastname: Shimoyama
authors.forename: T
authors.initials: T
authors.lastname: Noda
authors.forename: S
authors.initials: S
authors.lastname: Uchida
authors.forename: Z
authors.initials: Z
authors.lastname: Hussain
authors.forename: Z X
authors.initials: ZX
authors.lastname: Shen