Investigations on the relationship between $T_c$ and the superconducting gap under magnetic and non-magnetic impurity substitutions in YBa$_2$Cu$_3$O$_{7-\delta}$

TL;DR

This study uses electronic Raman scattering to explore how magnetic and non-magnetic impurities affect the superconducting gap and critical temperature in YBa2Cu3O7, revealing a decoupling between gap features and Tc.

Contribution

It provides new insights into the impurity effects on the superconducting gap structure and its relation to Tc in high-temperature superconductors.

Findings

Antinodal peak energy is not related to Tc under impurity substitution.

Superconductivity signatures vanish in the nodal regions with impurities.

Evidence suggests the presence of gapless arcs around the nodes.

Abstract

We report electronic Raman scattering measurements on optimally doped YBa2Cu3O7 where Zn or Ni impurities have been substituted by Cu. Using Raman selection rules, we have probed the superconducting gap in the nodal and antinodal regions. We show that under impurity substitutions, the energy of the antinodal peak detected in the superconducting state is not related to the critical temperature Tc and that signatures of superconductivity disappear in the nodal regions. Our experimental findings advocate in favor of gapless arcs around the nodes. The breakdown of the relationship between the antinodal gap amplitude and Tc is discussed in terms of local superconducting gap and pseudogap.