Local moment formation in zinc doped cuprates

TL;DR

This paper investigates how zinc impurities in cuprate superconductors can form local magnetic moments, challenging the assumption of a fixed valency, by modeling impurity effects within a Hubbard framework.

Contribution

It introduces a model considering variable zinc valency influenced by the medium, explaining local moment formation and spin susceptibility changes in doped cuprates.

Findings

Zinc impurities can induce local magnetic moments in cuprates.

The impurity valency is medium-dependent rather than fixed at 2+.

Modification of spin susceptibility near impurities was observed.

Abstract

We suggest that when zinc is substituted for copper in the copper oxide planes of high $T_{c}$ superconductors, it does not necessarily have a valency of 2+. Rather, the valency of a zinc impurity should be determined by its surrounding medium. In order to study this hypothesis, we examine the effect of static impurities inducing diagonal disorder within a one band Hubbard model coupled to a localised state. We use this model to discuss the physics of zinc doping in the cuprates. Specifically, we discuss the formation of local moments near impurity sites and the modification of the transverse spin susceptibility in the antiferromagnetic state.