Nuclear spin-lattice relaxation rate in noncentrosymmetric superconductor Y$_2$C$_3$

TL;DR

This paper models the nuclear spin-lattice relaxation rate in the noncentrosymmetric superconductor Y$_2$C$_3$, revealing how parity-mixing affects quasiparticle excitations and matches experimental observations.

Contribution

It introduces a parity-mixing model with spin-singlet and triplet components, explaining the anomalous relaxation rate behavior in Y$_2$C$_3$.

Findings

Distinct nodal structures due to parity-mixing

Noninteger power laws in relaxation rate at low temperatures

Qualitative agreement with experimental data

Abstract

For a noncentrosymmetric superconductor such as Y$_2$C$_3$, we consider a parity-mixing model composed of spin-singlet s-wave and spin-triplet f-wave pairing components. The $d$-vector in f-wave state is chosen to be parallel to the Dresselhaus asymmetric spin-orbit coupling vector. It is found that, the quasiparticle excitation spectrum exhibits distinct nodal structure as a consequence of parity-mixing. Our calculation predict anomalous noninteger power laws for low-temperature nuclear spin-lattice relaxation rate $T_{1}^{-1}$. We demonstrate particularly that such a model can qualitatively account for the existing experimental results of the temperature dependence of $T_{1}^{-1}$ in Y$_2$C$_3$.