Linear and nonlinear electrodynamic response of bulk CaC6 in the microwave regime

TL;DR

This study investigates the microwave linear and nonlinear electrodynamic responses of CaC6 superconductors, revealing their weakly-coupled, fully gapped nature and potential for microwave applications.

Contribution

It provides the first detailed measurements of CaC6's microwave surface resistance and nonlinear response, highlighting its suitability for microwave technology.

Findings

CaC6 behaves as a weakly-coupled, fully gapped superconductor.

Surface resistance Rs shows weak power dependence.

Potential for CaC6 as an alternative to Nb in microwave devices.

Abstract

The linear and nonlinear response to a microwave electromagnetic field of two c-axis oriented polycrystalline samples of the newly discovered superconductor CaC6 (Tc = 11.5 K) is studied in the superconducting state down to 2 K. The surface resistance Rs and the third order intermodulation distortion, arising from a two-tone excitation, have been measured as a function of temperature and microwave circulating power. Experiments are carried out using a dielectrically loaded copper cavity operating at 7 GHz in a "hot finger" configuration. The results confirm recent experimental findings that CaC6 behaves as a weakly-coupled, fully gapped, superconductor. The weak power dependence of Rs encourages a further investigation of this novel superconductor as a possible alternative to Nb in specific microwave applications.