Enhancing the superconducting transition temperature of the heavy fermion compound CeIrIn5 in the absence of spin correlations -: art. no. 037007

We report on a pressure- (P-)induced evolution of superconductivity and spin correlations in CeIrIn5 via the In-115 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-c increases to T-c=0.8 K, which is twice T-c (P=0 GPa), 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 CeIrIn5.