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

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.

New expanded version including analysis and comparison of phonon softening to diagrammatic theory