Anomalous phonons in oriented film samples of Y-Ba-Cu-O

Abstract We prepared two epitaxial films of YBa 2 Cu 3 O 7 , in which the C -axes are oriented either perpendicular or parallel to the film surfaces. The anomalous phonon properties in the epitaxial films superconductor annealed from Ar and O 2 atmospheres were observed by means of IR reflection spectroscopy. We classified more clearly phonons or orthorhombic phase to be two modes, including E ⊥ C and E // C modes, than using polycrystalline samples. The strong coupling between the phonons and carriers reduces the IR activity of phonons. The important role of the phonon in superconductivity is shown and this may provide a crucial clue to the mechanism study.