title: Phonon screening in high-temperature superconductors
abstract: In good conductors optical phonons are usually screened, and therefore not observed. However, sharp features due to infrared-active modes in the copper-oxygen planes are observed in the optical conductivity of Pr1.85Ce0.15CuO4 and YBa2Cu3O6.95. Oscillator strengths indicate that the screening of these modes is poor or totally absent. These materials are compared with eta-Mo4O11, in which lattice modes appear suddenly below the charge-density wave transition. It is proposed that poor screening in the cuprates originates from fluctuating charge inhomogeneities in the copper-oxygen planes.
authors.affiliation: Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.initials: CC
authors.lastname: Homes
authors.initials: AW
authors.lastname: McConnell
authors.initials: BP
authors.lastname: Clayman
authors.initials: DA
authors.lastname: Bonn
authors.initials: R
authors.lastname: Liang
authors.initials: WN
authors.lastname: Hardy
authors.initials: M
authors.lastname: Inoue
authors.initials: H
authors.lastname: Negishi
authors.initials: P
authors.lastname: Fournier
authors.initials: RL
authors.lastname: Greene