Enhancing the Superconducting Transition Temperature in the Absence of Spin Correlations in Heavy Fermion Compound CeIrIn${}_5$

Abstract

We report on a pressure($P$)-induced evolution of superconductivity and spin correlations in CeIrIn${}_5$ via the ${}^{115}$In 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 GPa, $T_{\mathrm{c}}$ increases to $T_{\mathrm{c}}$ = 0.8 K that is twice $T_{\mathrm{c}}$($P$ = 0 GPa), in the background of Fermi liquid state. This is in sharp contrast with the previous case in which negative, chemical pressure (replacing Ir with Rh) enhances magnetic interaction and increases $T_{\mathrm{c}}$. Our results suggest that multiple mechanisms work to produce superconductivity in the same compound CeIrIn${}_5$.

4pages, 4figures, accepted for publication in Phys. Rev. Lett