Temperature versus Sm concentration phase diagram and quantum criticality in the correlated electron system Ce1−xSmxCoIn5

Abstract

We report electrical resistivity, magnetization, and specific heat measurements on the correlated electron system ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Sm}}_{x}{\mathrm{CoIn}}_{5}$ ($0\ensuremath{\le}x\ensuremath{\le}1$). Superconductivity (SC) in the heavy-fermion compound ${\mathrm{CeCoIn}}_{5}$, which is suppressed with increasing Sm concentration $x$, and antiferromagnetic (AFM) order of ${\mathrm{SmCoIn}}_{5}$, which is suppressed with decreasing $x$, converge near a quantum critical point at ${x}_{\mathrm{QCP}}\ensuremath{\approx}0.15$, with no indication of coexistence of SC and AFM in the vicinity of the QCP. Non-Fermi-liquid (NFL) behavior is observed in the normal-state electrical resistivity, $\ensuremath{\rho}(T)$, and specific heat, $C(T)$, in the vicinity of the QCP; e.g., the coefficient and the exponent of the power-law $T$ dependence of $\ensuremath{\rho}(T)$ exhibit pronounced maxima and minima, respectively, at ${x}_{\mathrm{QCP}}$, while $C(T)/T$ exhibits a logarithmic divergence in $T$ at ${x}_{\mathrm{QCP}}$. A low-temperature upturn in $\ensuremath{\rho}(T)$ develops in the range $0.70\ensuremath{\le}x\ensuremath{\le}0.85$ which is reminiscent of a single impurity Kondo effect, suggesting that Sm substitution tunes the relative strength of competing Kondo and Ruderman-Kittel-Kasuya-Yosida energy scales. The suppression of SC with increasing $x$ is probably associated with the exchange interaction between the Ce quasiparticles involved in the superconductivity and the magnetic moments of the Sm ions.