Magnetic Field Dependence of the Spin Susceptibility on Conventional s-wave Superconductor LaRu$_4$P$_{12}$ Revealed by $^{31}$P-NMR and $^{139}$La-NMR

TL;DR

This study investigates how the spin susceptibility in the conventional s-wave superconductor LaRu$_4$P$_{12}$ varies with magnetic field using NMR, revealing a proportional relationship indicative of orbital pair-breaking effects.

Contribution

It provides the first detailed NMR analysis of the magnetic field dependence of spin susceptibility in LaRu$_4$P$_{12}$, confirming theoretical expectations for orbital pair-breaking effects.

Findings

Spin susceptibility is proportional to magnetic field in the superconducting state.

The spin susceptibility connects smoothly to the normal state.

Results exemplify orbital pair-breaking in conventional superconductors.

Abstract

The magnetic field dependence of the spin part of Knight shift, which is proportional to the superconducting-state spin susceptibility, was investigated at two nuclear sites, $^{31}$P and $^{139}$La in a conventional s-wave superconductor LaRu$_4$P$_{12}$. After the analyses, we confirmed that the superconducting-state spin susceptibility is proportional to magnetic field, and connects to the normal-state spin susceptibility smoothly. This is a textbook example, when the superconductivity is broken with the orbital pair-breaking effect.