Observations of a pseudogap in the c-axis electronic Raman continuum of YBa2Cu4O8 single crystals -: art. no. 100508

We report the results of c-axis polarized electronic Raman scattering measurements on single crystals of YBa2Cu4O8. As the temperature is lowered we find a monotonic depletion of spectral weight below a Raman shift of around 900 cm(-1), consistent in character with the pseudogap, but unaffected by the onset of superconductivity. We also establish that the c-axis continuum in YBa2Cu4O8 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.