MILLIMETER-WAVE COMPLEX CONDUCTIVITY OF SOME EPITAXIAL YBA2CU3O7-SIGMA FILMS

The first complex conductivities (*) of epitaxial and partly oriented Y-Ba-Cu-O films have been measured at 60 GHz. For the epitaxial films, the real part of the conductivity, 1, shows a maximum just below the superconducting transition. The qualitative behavior of * is not consistent with classical BCS calculations for a homogeneous superconducting film. Large variations in the temperature dependence of * among these films suggest that they are mixtures of normal and superconducting regions. A surface resistance of 10-3 at 38 K and a penetration depth of 0.4 m at 55 K have been determined. © 1990 The American Physical Society.