Spin wave contribution to the nuclear spin-lattice relaxation in triplet superconductors

TL;DR

This paper investigates how collective spin wave excitations in triplet superconductors influence nuclear spin-lattice relaxation, revealing a power-law temperature dependence that varies with system dimensionality.

Contribution

It introduces an effective bosonic model for spin waves in triplet superconductors and estimates their impact on nuclear relaxation rates in specific materials.

Findings

Spin wave excitations have frequencies of 1-20 GHz in studied materials.

The relaxation rate 1/T_1 scales as T^3 in 2D and T^5 in 3D systems.

Spin waves significantly contribute to nuclear relaxation in triplet superconductors.

Abstract

We discuss collective spin wave excitations in triplet superconductors with an easy axis anisotropy for the order parameter. Using a microscopic model for interacting electrons we estimate the frequency of such excitations in Bechgaard salts and ruthenate superconductors to be one and twenty GHz respectively. We introduce an effective bosonic model to describe spin-wave excitations and calculate their contribution to the nuclear spin lattice relaxation rate. We find that in the experimentally relevant regime of temperatures, this mechanism leads to the power law scaling of 1/T_1 with temperature. For two and three dimensional systems the scaling exponents are three and five respectively. We discuss experimental manifestations of the spin wave mechanism of the nuclear spin lattice relaxation.