Enhancing the Superconducting Transition Temperature of the Heavy Fermion CompoundCeIrIn5in the Absence of Spin Correlations

Abstract

We report on a pressure- ($P$-)induced evolution of superconductivity and spin correlations in ${\mathrm{C}\mathrm{e}\mathrm{I}\mathrm{r}\mathrm{I}\mathrm{n}}_5$ via the ${}^{115}\mathrm{I}\mathrm{n}$ nuclear-spin-lattice-relaxation rate measurements. We find that applying pressure suppresses dramatically the antiferromagnetic fluctuations that are strong at ambient pressure. At $P=2.1\mathrm{G}\mathrm{P}\mathrm{a}$, $T_c$ increases to $T_c=0.8\mathrm{K}$, which is twice $T_c$ ($P=0\mathrm{G}\mathrm{P}\mathrm{a}$), in the background of Fermi-liquid state. This is in sharp contrast to the previous case in which a negative, chemical pressure (replacing Ir with Rh) enhances magnetic interaction and increases $T_c$. Our results suggest that multiple mechanisms work to produce superconductivity in the same compound ${\mathrm{C}\mathrm{e}\mathrm{I}\mathrm{r}\mathrm{I}\mathrm{n}}_5$.