On Heavy Fermion Superconductivity and Quantum Criticality in the 115 series

We have performed a detailed analysis of the optical properties of the 1-1-5 series (CeTIn5 where T=Co,Ir,Rh), revealing the hybridization gap ($\Delta$) as key to understanding their rich phase diagram. Surprisingly we find that $\Delta$ for only one of the four bands crossing the Fermi surface determines the properties of the system. Furthermore, these carriers are the lightest and produce the smallest $\Delta$. Additionally we discuss connections between this $\Delta$, the superconducting transition temperature and the symmetry of the superconducting gap. This study demonstrates an experimental link between superconductivity and the parameter governing the magnetic Quantum Critical Point.