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

TL;DR

Applying pressure to CeIrIn$_5$ suppresses spin fluctuations and enhances superconductivity, indicating multiple mechanisms contribute to its superconducting state.

Contribution

This study reveals that pressure can increase $T_c$ in CeIrIn$_5$ despite suppressing spin correlations, challenging previous assumptions about their role.

Findings

Pressure suppresses antiferromagnetic fluctuations in CeIrIn$_5$.

Superconducting transition temperature $T_c$ doubles at 2.1 GPa.

Multiple mechanisms may induce superconductivity in 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, $T_{\rm c}$ increases to $T_{\rm c}$ = 0.8 K that is twice $T_{\rm c}$($P$ = 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 $T_{\rm c}$. Our results suggest that multiple mechanisms work to produce superconductivity in the same compound CeIrIn$_5$.