Pressure-induced anomalous magnetism and unconventional superconductivity inCeRhIn5:115In-NQR study under pressure

Abstract

We report ${}^{115}\mathrm{In}$ nuclear-quadrupole-resonance (NQR) measurements of the pressure $\mathrm{}\left(P\right)\mathrm{}$-induced superconductor ${\mathrm{CeRhIn}}_5$ in the antiferromagnetic (AF) and superconducting (SC) states. In the AF region, the internal field $H_{\mathrm{int}}$ at the In site is substantially reduced from $H_{\mathrm{int}}=1.75\mathrm{}\mathrm{kOe}$ at $P=0\mathrm{}$ to 0.39 kOe at $P=1.23\mathrm{}\mathrm{GPa},$ while the Néel temperature slightly changes with increasing P. This suggests that either the size in the ordered moment $M_Q\mathrm{}\left(P\right)\mathrm{}$ or the angle $\theta \mathrm{}\left(P\right)\mathrm{}$ between the direction of $M_Q\mathrm{}\left(P\right)\mathrm{}$ and the tetragonal c axis is extrapolated to zero at $P^{*}=1.6\mathrm{}\pm 0.1\mathrm{GPa}$ at which a bulk SC transition is no longer emergent. In the SC state at $P=2.1\mathrm{}\mathrm{GPa},$ the nuclear spin-lattice relaxation rate ${}^{115}{(1/T}_1)$ has revealed a $T^3$ dependence without the coherence peak just below $T_c,$ giving evidence for the unconventional superconductivity. The dimensionality of the magnetic fluctuations in the normal state is also discussed.