Kondo coherence and superconductivity in Yb doped CeCoIn$_5$

We have studied the effect of Yb doping on superconductivity in the unconventional heavy fermion superconductor CeCoIn$_5$ in a doping series spanning from pure CeCoIn$_5$ to the paramagnetic metal YbCoIn$_5$, which is isostructural with CeCoIn$_5$. By replacing Ce by Yb, we are at the same time removing carriers as well as disrupting the Kondo lattice of CeCoIn$_5$, which is thought to be responsible for superconductivity in this compound. This will give us insight into how the Kondo coherence and Cooper pair breaking in CeCoIn$_5$ are affected by Yb substitution. Our doping series shows that the unit cell volume stays approximately constant up to a Yb concentration of about 40~\%. At higher Yb concentrations the unit cell volume begins to shrink gradually to the value of YbCoIn$_5$. However, is superconductivity in the doped system is remarkably resilient against Yb substitution: At low doping the superconducting transition temperature $T_c$ is only gradually suppressed from the value of 2.24~K of pure CeCoIn$_5$, and only with a Yb concentration of 60~\% $T_c$ is suppressed below 0.3~K.