Comparative study of superconducting energy gaps in oriented films and polycrystalline bulk samples of Y-Ba-Cu-O

A study of infrared reflectivity from an epitaxial film of Y1Ba2Cu3O(7-x) in which the c axis is primarily oriented perpendicular to the film surface, and from bulk polycrystalline samples with no orientation, has been made. In the oriented film the region of enhanced reflectivity associated with the superconducting energy gap extends to 400/cm (50 meV) compared with only 200/cm in the bulk material. The energy gap for the film is estimated to be 2 Delta = (4.7 + or - 1.2)kTc, a value which is consistent with recent tunneling measurements and with strong-coupling superconductivity. (Author)