Evidence of a quantum critical point in Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ alloys at high Yb doping*

We performed this study on single crystals of Ce$_{\mathrm{1-x}}$Yb$_{x}$CoIn$_{5}$ alloys with the motivation to further explore some of the previously reported unusual behaviors such as robust coherence and superconductivity, non-Fermi liquid (NFL) behavior, and the possibility of quantum criticality in higher Yb doping. Our specific heat and electronic magneto-transport measurements on the alloy with x $=$ 0.75 nominal doping down to temperatures (T) as low as 0.5 K and magnetic fields (H) as high as 14 T. Our analysis of both specific heat and resistivity data unveils the presence of a crossover from NFL behavior at high temperatures to Fermi-liquid (FL) behavior at lower temperatures. Our analysis also indicates that the origin of the NFL behavior is a result of quantum fluctuations of unknown origin. The H-T phase diagram extracted from resistivity and specific heat shows that the crossover from NFL to FL behavior at zero temperature occurs at H $=$ 0. This implies that the alloy with x $=$ 0.75 Yb concentration is quantum critical, i.e., x$_{\mathrm{c}} = $ 0.75. This result of zero field quantum critical point at x $=$ 0.75 is also confirmed from our analysis of magneto-resistance data.