Microwave Spectroscopy of Heavy Fermion Superconductors at MilliKelvin Temperatures

Heavy fermion metals are of immense interest due to the extreme renormalization of quasiparticle mass, the possibility of non-Fermi-liquid physics, and the appearance of superconductivity on the verge of magnetic order, in the vicinity of quantum critical points. We have setup a novel system for high resolution microwave spectroscopy at milliKelvin temperatures, across the frequency range 2 to 40 GHz. We are using this to study the unconventional superconducting states in a number of Ce- and U-based heavy fermion compounds. I will present an overview of the microwave spectroscopy system, and a summary of some of the interesting physics we have observed in these systems.