Electronic Raman scattering in Y1-xCaxBa2Cu3O7-δ single crystals

Polarized Raman scattering measurements have been performed on single crystals of the high temperature superconductor Y0.8Ca0.2Ba2Cu3O7-δ as a function of carrier concentration. For strongly overdoped crystals we found that positions of the pair-breaking peaks decrease with increasing overdoping and, unlike in optimally doped crystals, almost coincide. In both doping states the Raman response follows a linear power law at low frequencies for the A1g channel and a αω + βω3 dependence for the B1g one. Our results agree with similar data on overdoped Bi-2212 and Tl-2201, and should therefore represent a universal property of the overdoped cuprate high-Tc superconductors. For the strongly underdoped sample, no superconductivity-induced change in the electronic continuum has been observed. (orig.)