IR SPECTROSCOPY OF METAL-OXIDE SUPERCONDUCTORS IN NORMAL AND SUPERCONDUCTING STATES

Normal state reflectivity of YBa2Cu3O6.9 and Bi2Sr2CaCu2O8+y single crystals has been studied by means of polarized light spectroscopy in mid- and far-infrared. The obtained data show that inplane conductivity of both compounds is metal-like and differs drastically from the out-of-plane one thus giving the direct evidence of electronic structure of these systems to be quasi two dimensional (2D). The analysis of low-temperature reflectivity of YBa2Cu3O6.9 crystalline films and ceramic samples indicates the anisotropy of the energy gap with 2π value in (ab) plane and perpendicular to (ab) plane being equal 7.5kTc and 3.5kTc respectively. The obtained anisotropy of the energy gap and of normal state reflectivity proves the hypothesis of 2D superconductivity in YBa2Cu3O6.9. © 1990.