Two-dimensional XY-type Magnetic Properties of Locally Noncentrosymmetric Superconductor CeRh$_2$As$_2$

TL;DR

This study reveals that CeRh$_2$As$_2$ exhibits two-dimensional antiferromagnetic fluctuations and easy-plane magnetic anisotropy, which are potentially crucial for its unique multi-phase superconductivity.

Contribution

The paper provides the first detailed NMR investigation showing 2D magnetic correlations in CeRh$_2$As$_2$, highlighting their significance in its superconducting behavior.

Findings

Easy-plane magnetic anisotropy observed

Temperature dependence of $1/T_1$ indicates 2D antiferromagnetic fluctuations

Spatially 2D magnetic correlations are rare among heavy-fermion superconductors

Abstract

We performed $^{75}$As-NMR measurements to investigate the normal-state magnetic properties of CeRh$_2$As$_2$, a recently-discovered heavy-fermion superconductor. The magnitude and temperature dependence of the Knight shift at the As(2) site indicate easy-plane-type magnetic anisotropy in CeRh$_2$As$_2$. With regard to spin fluctuations, the temperature dependence of the nuclear spin-lattice relaxation rate $1/T_1$ arising from the 4$f$ electrons decreases from high-temperature constant behavior on cooling at $\sim$ 40~K, which is typical behavior of heavy-fermion systems. In addition, $1/T_1$ becomes constant at low temperatures, suggesting spatially two-dimensional antiferromagnetic fluctuations. Two-dimensional magnetic correlations in the real space are quite rare among heavy-fermion superconductors, and they may be a key factor in the unique superconducting multi-phase in CeRh$_2$As$_2$.