Evidence for Novel Pairing State in Noncentrosymmetric Superconductor CePt3Si: 29Si-NMR Knight Shift Study

TL;DR

This study provides evidence for a novel two-component pairing state in the noncentrosymmetric superconductor CePt3Si, indicated by unchanged Knight shift across T_c and a mixed spin-singlet and triplet order parameter.

Contribution

It demonstrates the presence of a two-component order parameter in CePt3Si, combining spin-singlet and triplet pairing, supported by Knight shift and relaxation measurements.

Findings

Knight shift remains unchanged across T_c for H along c-axis.

Nuclear spin-lattice relaxation suggests mixed pairing state.

Data supports a two-component order parameter in CePt3Si.

Abstract

We report the measurements of the $^{29}$Si Knight shift $^{29}K$ on the noncentrosymmetric heavy-fermion compound CePt$_{3}$Si in which antiferromagnetism (AFM) with $T_{\rm N}=2.2$ K coexists with superconductivity (SC) with $T_{c}=0.75$ K. Its spin part $^{29}K_{\rm s}$, which is deduced to be $K_{\rm s}^{c}\ge 0.11$ and 0.16% at respective magnetic fields $H=2.0061$ and 0.8671 T, does not decrease across the superconducting transition temperature $T_{c}$ for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of $^{195}$Pt below $T_{c}$ has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePt$_{3}$Si.