Infrared studies of high Tc superconductors

The authors discuss the IR reflectance of epitaxially grown laser-deposited films of YBa2Cu3O7-δ and of single crystals of Bi2Sr2CaCu2O8. Below Tc, both show zero absorption at low frequencies (120-140 cm for YBa2Cu3O7-δ and 250-300/cm for bisco). At higher frequencies (420-470/cm for YBa2Cu3O7-δ and 470-520/cm for bisco), there is a characteristic knee in the reflectance and a corresponding minimum in σ1(ω). Although these features are …