Theory for ultrafast nonequilibrium dynamics in d-wave superconductors

TL;DR

This paper employs density-matrix theory to model the ultrafast nonequilibrium dynamics in d-wave superconductors, predicting spectral regimes and effects of electron-phonon interactions from a microscopic perspective.

Contribution

It introduces a microscopic theoretical framework for ultrafast dynamics in d-wave superconductors, including spectral predictions and the role of electron-phonon coupling.

Findings

Identification of three spectral regimes in ultrafast response

Prediction of a suppressed pair-breaking peak at high energies

Derivation of rate equations incorporating electron-phonon effects

Abstract

We use density-matrix theory to calculate the ultrafast dynamics of unconventional superconductors from a microscopic viewpoint. We calculate the time evolution of the optical conductivity as well as pump-probe spectra for a d-wave order parameter. Three regimes can be distinguished in the spectra. The Drude response at low photon energies is the only one of those which has been measured experimentally so far. At higher energies, we predict two more regimes: the pair-breaking peak, which is reduced as Cooper-pairs are broken up by the exciting pulse; and a suppression above the pair-breaking peak due to nonequilibrium quasiparticles. Furthermore, we consider the influence of the electron-phonon coupling, and derive rate equations which have been widely used so far.