Niobium stripline resonators for microwave studies on superconductors

TL;DR

This paper explores niobium-based microwave stripline resonators for studying superconductors, demonstrating their effectiveness in measuring complex conductivity and energy gaps, and comparing results with lead resonators.

Contribution

It introduces niobium stripline resonators for microwave spectroscopy of superconductors and compares their performance with lead resonators, advancing measurement techniques.

Findings

Determined the temperature dependence of niobium's complex conductivity.

Measured the energy gap of niobium as 2.1 meV.

Successfully detected the superconducting transition of tantalum.

Abstract

Microwave spectroscopy is a powerful experimental tool to reveal information on the intrinsic properties of superconductors. Superconducting stripline resonators, where the material under study constitutes one of the ground planes, offer a high sensitivity to investigate superconducting bulk samples. In order to improve this measurement technique, we have studied stripline resonators made of niobium, and we compare the results to lead stripline resonators. With this technique we are able to determine the temperature dependence of the complex conductivity of niobium and the energy gap $\Delta(0)=2.1$ meV. Finally we show measurements at the superconducting transition of a tantalum bulk sample using niobium stripline resonators.