Zn-induced in-gap electronic states in La214 probed by uniform magnetic susceptibility: relevance to the suppression of superconducting Tc

TL;DR

This study investigates how Zn substitution in cuprate superconductors creates in-gap electronic states that suppress superconductivity, supporting the idea that these states are weakly localized quasiparticles affecting Tc.

Contribution

The paper provides evidence that Zn induces in-gap electronic states in La214, linking these states to the suppression of superconducting Tc, and supports the quasiparticle localization scenario.

Findings

Zn substitution enhances low-temperature magnetic susceptibility.

In-gap electronic states are associated with Zn in cuprates.

Suppression of Tc correlates with the extent of susceptibility enhancement.

Abstract

Substitution of isovalent non-magnetic defects, such as Zn, in CuO2 plane strongly modifies the magnetic properties of strongly electron correlated hole doped cuprate superconductors. The reason for enhanced uniform magnetic susceptibility, \c{hi}, in Zn substituted cuprates is debatable. So far, the observed magnetic behavior has been analyzed mainly in terms of two somewhat contrasting scenarios, (a) that due to independent localized moments appearing in the vicinity of Zn arising because of the strong electronic/magnetic correlations present in the host compound and (b) that due to transfer of quasiparticle spectral weight and creation of weakly localized low energy electronic states associated with each Zn atom in place of an in-plane Cu. If the second scenario is correct, one should expect a direct correspondence between Zn induced suppression of superconducting transition temperature, Tc, and the extent of the enhanced magnetic susceptibility at low temperature. In this case, the low-T enhancement of \c{hi} would be due to weakly localized quasiparticle states at low energy and these electronic states will be precluded from taking part in Cooper pairing. We explore this second possibility by analyzing the \c{hi}(T) data for La2-xSrxCu1-yZnyO4 with different hole contents, p (= x), and Zn concentrations (y) in this paper. Results of our analysis support this scenario.