Effects of Magnetic and non-Magnetic Impurities on the Superconducting State of YBa$_{2}$Cu$_{3}$O$_{7-\delta}$

TL;DR

This study investigates how magnetic and non-magnetic impurities, Zn and Ni, affect the superconducting properties of YBa₂Cu₃O₇−δ, revealing that the superconducting gap remains unchanged while collective modes vary with impurities.

Contribution

It provides new insights into the impurity effects on superconducting gap and collective modes in YBCO, highlighting the different behaviors of magnetic and non-magnetic impurities.

Findings

Superconducting gap energy is unaffected by Zn and Ni substitutions.

The A₁g collective mode follows the critical temperature with different slopes for Zn and Ni.

The A₁g mode correlates with the magnetic resonance observed in neutron scattering.

Abstract

We report Electronic Raman Scattering measurements on optimally doped Zn and Ni substituted YBCO in A$_{1g}$ and B$_{1g}$ channels. We show that the superconducting gap energy is independant of magnetic Ni and non-magnetic Zn substitutions. On the contrary the collective A$_{1g}$ mode follows the critical temperature $T_c$ with two distinct slopes for Ni and Zn, and tracks the magnetic resonance seen in inelastic neutron scattering. We explain the unconventionnal energy dependence of the superconducting gap and discuss the behaviour of the A$_{1g}$ mode within magnetic and non-magnetic impurities.