The pseudogap and superconducting gap in the ab-plane electronic Raman continuum of YBa2Cu4O8

We report plane-polarised Raman spectra from YBa₂Cu₄O₈ single crystals between 300 and 10 K. In the normal state we observe a gap-like depletion of intensity from the electronic continuum extending to around 1200 cm⁻¹ with an onset temperature of around 225 K. We remove the phonons and pseudogap depletion from the spectra using a simple model and recover a characteristic high-T_c superconductor continuum. In the superconducting state, intensity returns to the continuum in the form of a very broad pair-breaking peak.