ELECTRONIC RAMAN-SCATTERING IN YBA2CU4O8 AT HIGH-PRESSURE

We have investigated the electronic Raman scattering in YBa2Cu4O8 at h ydrostatic pressures up to 9 GPa. At pressures below 1.5 GPa, the cont inuum in the normal state is strongly temperature dependent in all thr ee polarization configurations measured. This temperature dependence f ollows a Bose-Einstein form, consistent with the earlier report of Don ovan et al. With increasing pressure, the temperature dependence impli ed by the Bose-Einstein factor gradually decreases, and above 6 GPa th e electronic continuum of the normal state becomes very weakly tempera ture dependent in all three configurations, an effect which is also ob served in YBa2Cu3O7 at ambient pressure. With increasing pressure, YBa 2Cu4O8 is generally believed to be tuned from underdoped to optimally doped. Given this scenario, we can explain our results within a model recently proposed by Varma, who suggests there is a crossover from the Fermi-Liquid to the so-called Marginal-Fermi-Liquid when the supercon ducting cuprates are tuned toward optimal doping. Additionally, we rep ort on the pressure dependent rearrangement of the continuum which occ urs below T-c. Copyright (C) 1996 Elsevier Science Ltd.