Complex microwave conductivity of Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ thin films using a cavity perturbation method

摘要

We report a study of the microwave conductivity of electron-dopedPr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ superconducting thin films using acavity perturbation technique. The relative frequency shifts obtained for thesamples placed at a maximum electric field location in the cavity are treatedusing the high conductivity limit presented recently by Peligrad $\textit{et}$$\textit{al.}$ Using two resonance modes, TE$_{102}$ (16.5 GHz) and TE$_{101}$(13 GHz) of the same cavity, only one adjustable parameter $\Gamma$ is neededto link the frequency shifts of an empty cavity to the ones of a cavity loadedwith a perfect conductor. Moreover, by studying different sampleconfigurations, we can relate the substrate effects on the frequency shifts toa scaling factor. These procedures allow us to extract the temperaturedependence of the complex penetration depth and the complex microwaveconductivity of two films with different quality. Our data confirm that all thephysical properties of the superconducting state are consistent with an orderparameter with lines of nodes. Moreover, we demonstrate the high sensitivity ofthese properties on the quality of the films.