OPTICAL REFLECTANCES AND DIELECTRIC FUNCTIONS OF YBA2CU3O7-DELTA SUPERCONDUCTORS AT VARIOUS TEMPERATURES

The temperature variations of the anisotropic dielectric functions for YBa2Cu3O7-delta epitaxial thin films are derived empirically from the optical reflectance within the wavelength region between infrared and UV. The optical transitions contain contributions from ionic vibratio ns, free electron oscillations, and inter- and intraband transitions. The two-fluid model is exploited to distinguish the foe electron contr ibutions between the normal state and the superconducting state. The d ielectric functions and the fitting parameters established in this wor k can be implemented to calculate the optical refractive indices at va rious temperatures and frequencies.