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

The linear and nonlinear responses to a microwave electromagnetic field of two c-axis oriented polycrystalline samples of the recently discovered superconductor CaC6 (T-C approximate to 11.5 K) is studied in the superconducting state down to 2 K. The surface resistance R-S 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. (C) 2007 American Institute of Physics.