80–111 GHz quasi-optical measurement of the complex conductivities of YBa2Cu3O7 superconducting thin films

Abstract
Complex conductivities of YBa2Cu3O7 high‐temperature superconducting thin films were measured from 80 to 111 GHz using quasi‐optical techniques. From transmission measurements, a peak was obtained in σ1 versus temperature. Measurements of the frequency dependence of this peak position found it shifted to higher temperatures with increasing frequency. The data for both σ1 and σ2, as a function of frequency, were fitted using a BCS/effective medium model. This fit indicates that the observed peak in σ1 is a result of the temperature dependence of the carrier mean free path combined with effects resulting from the granularity of the films.