Evidence for re-entrant, zero field quantum critical point, with chemical tuning in Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$*

We performed specific heat and electronic transport studies on single crystals of Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ alloys with the motivation to probe further, some of the previously reported unusual behaviors, such as robust coherence and superconductivity, persistent non-Fermi liquid (NFL) behavior, and the possibility of quantum criticality in higher Yb doping. These measurements are performed in temperatures as low as 0.5 K and magnetic fields up to 14 T. Our analysis of specific heat and resistivity data unveils the presence of a crossover in the properties of x $=$ 0.54 doping crystals, from a high temperature NFL behavior to Fermi-liquid (FL) behavior at lower temperatures. We show that the origin of the NFL behavior is a result of quantum fluctuations. Our analysis also establishes that the alloy with x $=$ 0.54 Yb concentration is quantum critical, i.e., x$_{\mathrm{c}} = $ 0.54.