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

TL;DR

This study measures the microwave conductivity of Pr$_{1.85}$Ce$_{0.15}$CuO$_{4- ext{delta}}$ thin films using a cavity perturbation method, revealing details about the superconducting order parameter and the impact of film quality.

Contribution

It introduces a cavity perturbation technique with a single adjustable parameter to accurately determine the complex microwave conductivity of superconducting thin films.

Findings

Superconducting properties are consistent with a nodal order parameter.

Film quality significantly affects the microwave response.

Method effectively isolates substrate effects and extracts temperature-dependent properties.

Abstract

We report a study of the microwave conductivity of electron-doped Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ superconducting thin films using a cavity perturbation technique. The relative frequency shifts obtained for the samples placed at a maximum electric field location in the cavity are treated using 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 needed to link the frequency shifts of an empty cavity to the ones of a cavity loaded with a perfect conductor. Moreover, by studying different sample configurations, we can relate the substrate effects on the frequency shifts to a scaling factor. These procedures allow us to extract the temperature dependence of the complex penetration depth and the complex microwave conductivity of two films with different quality. Our data confirm that all the physical properties of the superconducting state are consistent with an order parameter with lines of nodes. Moreover, we demonstrate the high sensitivity of these properties on the quality of the films.