Observations of a pseudogap in thec-axis electronic Raman continuum ofYBa2Cu4O8single crystals

Abstract

We report the results of c-axis polarized electronic Raman scattering measurements on single crystals of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{4}{\mathrm{O}}_{8}.$ As the temperature is lowered we find a monotonic depletion of spectral weight below a Raman shift of around 900 ${\mathrm{cm}}^{\ensuremath{-}1},$ consistent in character with the pseudogap, but unaffected by the onset of superconductivity. We also establish that the c-axis continuum in ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{4}{\mathrm{O}}_{8}$ can be described by a simple relaxational response, without the inclusion of electron-phonon scattering effects. In contrast to the c-axis transport properties, the CuO chains appear to have little influence on the c-axis Raman continuum.