On the origin of the A$_{1g}$ and B$_{1g}$ electronic Raman scattering peaks in the superconducting state of YBa$_{2}$Cu$_{3}$O$_{7-\delta}$

TL;DR

This study investigates the origins of A₁g and B₁g electronic Raman peaks in YBa₂Cu₃O₇−δ superconductors, revealing impurity effects and supporting a theory linking these peaks to different order parameter fluctuations.

Contribution

It provides experimental evidence on impurity effects on Raman peaks and supports a theoretical model connecting these peaks to specific order parameter fluctuations.

Findings

A₁g peak intensity is impurity independent with a constant energy to T_c ratio.

B₁g peak is suppressed by non-magnetic Zn impurities.

Results support the theory linking Raman peaks to d-CDW and superconducting fluctuations.

Abstract

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.