Microwave complex resistivity of YBCO over a continuous frequency spectrum.

We present measurements of the complex resistivity of YBCO thin filmsas a function of frequency, in the microwave range. Data arecollected through a Corbino disc geometry, allowing for a continuousfrequency spectrum in the range 1-20 GHz. We focus on the behaviourof the imaginary part of the resistivity as a function of temperature. We show that it presents a broad peak justbelow Tc, whose amplitude and width depend on the frequency. Wealso discuss to what extent the experimental findings can be explainedusing the standard two fluid model, and which are the possibleresponsibles for the deviations from these predictions.