Relaxation of Hot Quasiparticles in a d-Wave Superconductor

TL;DR

This paper investigates how high-energy quasiparticles relax in a d-wave superconductor, revealing that pair-breaking processes are suppressed and relaxation mainly occurs via scattering with thermal quasiparticles, with specific temperature and intensity dependencies.

Contribution

It provides an analytical solution to the Boltzmann equation describing quasiparticle relaxation, highlighting the suppression of pair-breaking and the dominance of small-angle scattering at low temperatures.

Findings

Pair-breaking processes are forbidden in large momentum regions.

Umklapp scattering is exponentially suppressed at low temperatures.

Small-angle scattering leads to power-law relaxation behavior.

Abstract

Motivated by recent pump-probe experiments we consider the processes by which "hot" quasiparticles produced near the antinodes of a d-wave superconductor can relax. We show that in a large region of momentum space processes which break Cooper pairs are forbidden by energy and momentum conservation. Equilibration then occurs by scattering with thermal quasiparticles: Umklapp scattering is exponentially suppressed at low temperatures, but small-angle scattering leads to power-law behavior. By solving the Boltzmann equation analytically we make detailed predictions for the temperature and intensity dependence of these processes, which we compare with experiment.