Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity

TL;DR

This paper compares s-wave and d-wave gap symmetries in nonequilibrium superconductivity, analyzing classical models and experimental data to determine pairing symmetry in high-Tc cuprates.

Contribution

It reexamines classical models for nonequilibrium superconductivity, clarifies their predictions for different pairing symmetries, and evaluates their consistency with recent experiments.

Findings

D-wave gap suppression scales as n^{3/2}

Recent experiments conflict with d-wave pairing

Experiments do not support s-wave pairing either

Abstract

Recent application of ultrafast pump/probe optical techniques to superconductors has renewed interest in nonequilibrium superconductivity and the predictions that would be available for novel superconductors, such as the high-Tc cuprates. We have reexamined two of the classical models which have been used in the past to interpret nonequilibrium experiments with some success: the mu* model of Owen and Scalapino and the T* model of Parker. Predictions depend on pairing symmetry. For instance, the gap suppression due to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave as opposed to n for s-wave. Finally, we consider these models in the context of S-I-N tunneling and optical excitation experiments. While we confirm that recent pump/probe experiments in YBCO, as presently interpreted, are in conflict with d-wave pairing, we refute the further claim that they agree with s-wave.