Relaxation timescales and electron-phonon coupling in optically-pumped YBa$_2$Cu$_3$O$_{6+x}$ revealed by time-resolved Raman scattering

TL;DR

This study uses time-resolved Raman scattering to explore electron-phonon interactions and relaxation timescales in YBa₂Cu₃O₆₊ₓ, revealing strong coupling effects and transient phonon energy shifts under optical excitation.

Contribution

It demonstrates the application of pump-probe Raman scattering to directly measure electron-phonon coupling and phonon dynamics in a high-temperature superconductor.

Findings

Strong electron-phonon coupling observed

Phonon energy shifts align with theoretical predictions

Insights into photoinduced superconductivity at lower doping

Abstract

Time resolved measurements provide a new way to disentangle complex interactions in quantum materials due to their different timescales. We used pump-probe Raman scattering to investigate the apical oxygen vibration in YBa$_2$Cu$_3$O$_{6+x}$ under nonequilibrium conditions. Time-dependence of the phonon population demonstrated strong electron-phonon coupling. Most importantly, the phonon shifts to a higher energy due to transient smearing of the Fermi surface in a remarkable agreement with diagrammatic theory. We also discuss new insights into photoinduced superconductivity reported at lower doping that follow from these results.