Strong Coupling between Antiferromagnetic and Superconducting Order Parameters in CeRhIn$_5$ Studied by In-NQR Spectroscopy

TL;DR

This study reveals a strong coupling between antiferromagnetic and superconducting order parameters in CeRhIn$_5$, showing how pressure induces a transition from incommensurate to commensurate magnetism and enhances superconductivity.

Contribution

It demonstrates the pressure-induced evolution of magnetic order and its strong coupling with superconductivity in CeRhIn$_5$, using In-NQR spectroscopy.

Findings

Commensurate antiferromagnetism appears above 1.7 GPa.

Superconducting transition temperature increases as AFM moment decreases.

Evidence of strong coupling between AFM and SC order parameters.

Abstract

We report on a novel pressure ($P$)-induced evolution of magnetism and superconductivity (SC) in a helical magnet CeRhIn$_5$ with an incommensurate wave vector $Q_i=({1/2},{1/2},0.297)$ through the $^{115}$In nuclear quadrupole resonance (NQR) measurements under $P$. Systematic measurements of the $^{115}$In-NQR spectrum reveal that the commensurate antiferromagnetism (AFM) with $Q_c=({1/2},{1/2},{1/2})$ is realized above $P_m \sim$ 1.7 GPa. An important finding is that the size of SC gap and $T_c$ increase as the magnitude of the AFM moment decreases in the $P$ region, where SC uniformly coexists with the commensurate AFM. This result provides evidence of strong coupling between the commensurate AFM order parameter (OP) and SC OP.