Spin-lattice relaxation in the mixed state of YBaCuO: Can we see Doppler-shifted d-wave quasiparticles?

TL;DR

This paper investigates the mechanisms of spin-lattice relaxation in YBaCuO's mixed state, focusing on vortex vibrations and quasiparticle scattering, and finds that quasiparticle scattering partially explains experimental observations.

Contribution

It provides a detailed calculation of relaxation rates considering vortex vibrations and Doppler-shifted quasiparticles, highlighting the dominant relaxation mechanism in YBaCuO.

Findings

Vortex vibrations are too slow to significantly affect relaxation.

Electron spin-flip scattering partially agrees with experimental data.

Relaxation rates are position-dependent due to vortex presence.

Abstract

We present calculations of the rate of planar Cu spin lattice relaxation in the mixed state of YBaCuO due to (i) vortex vibrations and (ii) electron spin-flip scattering. We emphasize that both mechanisms give position dependent rates due to the presence of vortices, and hence the magnetization recovery is characterized by a distribution of rates. We conclude that relaxation by vortex vibrations is too slow to be a significant factor in this material. Using a semiclassical model of Doppler shifted d-wave quasiparticles with a linear dispersion around the nodes, our calculation of the relaxation rate from electron spin-flip scattering shows partial agreement with experiment.