Precision microwave spectroscopy of the heavy fermion superconductor CeCoIn$_{5}$ reveals nodal quasiparticle dynamics

CeCoIn$_{5}$ is a heavy fermion superconductor with strong similarities to the high-T$_{c}$ cuprates, including quasi-two-dimensionality, proximity to antiferromagnetism, and probable d-wave pairing arising from a non-Fermi-liquid normal state. Each system therefore forms an important testing ground for ideas relevant to the other system. Experiments that allow detailed comparisons of electronic properties are of particular interest. Here we use low temperature microwave spectroscopy to carry out a high-resolution study of the charge dynamics of the CeCoIn$_{5}$ superconducting state. The similarities to cuprates, in particular to ultra-clean YBa$_{2}$Cu$_{3}$O$_{y}$, are striking: the frequency and temperature dependence of the quasiparticle conductivity are instantly recognizable, a consequence of rapid suppression of quasiparticle scattering below T$_{c}$; and penetration depth data, when properly treated, reveal a clean, linear temperature dependence of the quasiparticle contribution to superfluid density. The measurements also expose key differences, including prominent multiband effects and a temperature-dependent mass renormalization.