  CeCoIn5 is a heavy fermion superconductor with strong similarities to the
high-Tc cuprates, including quasi-two-dimensionality, proximity to
antiferromagnetism, and probable d-wave pairing arising from a non-Fermi-liquid
normal state. Experiments allowing detailed comparisons of their electronic
properties are of particular interest, but in most cases are difficult to
realize, due to their very different transition temperatures. Here we use low
temperature microwave spectroscopy to study the charge dynamics of the CeCoIn5
superconducting state. The similarities to cuprates, in particular to
ultra-clean YBa2Cu3Oy, are striking: the frequency and temperature dependence
of the quasiparticle conductivity are instantly recognizable, a consequence of
rapid suppression of quasiparticle scattering below Tc; 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 renormalization of the quasiparticle mass.
