Unconventional Superconductivity in CeIrIn₅ and CeCoIn₅: Specific Heat and Thermal Conductivity Studies

Low temperature specific heat and thermal conductivity measurements on the ambient pressure heavy fermion superconductors CeIrIn₅ and CeCoIn₅ reveal power law temperature dependences of these quantities below T_c. The low temperature specific heat in both CeIrIn₅ and CeCoIn₅ includes T² 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 (CeIrIn₅), and a low temperature T³ variation in the clean limit (CeCoIn₅), also in accord with prediction for an unconventional superconductor with lines of nodes.