Unconventional Superconductivity inCeIrIn5andCeCoIn5: Specific Heat and Thermal Conductivity Studies

Low temperature specific heat and thermal conductivity measurements on the ambient pressure heavy fermion superconductors ${\mathrm{CeIrIn}}_5$ and ${\mathrm{CeCoIn}}_5$ reveal power law temperature dependences of these quantities below $T_c$. The low temperature specific heat in both ${\mathrm{CeIrIn}}_5$ and ${\mathrm{CeCoIn}}_5$ includes $T^2$ terms, consistent with the presence of nodes in the superconducting energy gap. The thermal conductivity data present a $T$-linear term consistent with the universal limit $\left({\mathrm{CeIrIn}}_5\right)$, and a low temperature $T^3$ variation in the clean limit $\left({\mathrm{CeCoIn}}_5\right)$, also in accord with prediction for an unconventional superconductor with lines of nodes.