On the origin of the A_(1g) and B_(1g) electronic Raman scattering peaks in the superconducting state of YBa₂Cu₃O_(7-δ)

The electronic Raman scattering has been investigated in optimally oxygen doped YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ single crystals as well as in crystals with non-magnetic, Zn, and magnetic, Ni, impurities. We found that the intensity of the A$_{1g}$ peak is impurity independent and their energy to $T_{c}$ ratio is almost constant ($2\Delta/k_{B}T_{c}\sim5$). Moreover, the signal at the B$_{1g}$ channel is completely smeared out when non-magnetic Zn impurities are present. These results are qualitatively interpreted in terms of the Zeyher and Greco's theory that relates the electronic Raman scattering in the A$_{1g}$ and B$_{1g}$ channels to \textit{d}-CDW and superconducting order parameters fluctuations, respectively.