States of Local Moment Induced by Nonmagnetic Impurities in Cuprate Superconductors

TL;DR

This paper models how nonmagnetic impurities induce local magnetic moments in cuprate superconductors, revealing dependence on impurity placement and interactions, with implications for experimental observations.

Contribution

It introduces a theoretical framework combining d-wave superconductivity and antiferromagnetic order to analyze impurity-induced magnetic moments in cuprates.

Findings

Single impurities induce local moments with S_z=0 or 1/2.

Two impurities at nearest neighbors produce zero net moment.

Impurity placement affects the magnitude and spin state of induced moments.

Abstract

By using a model Hamiltonian with d-wave superconductivity and competing antiferromagnetic (AF) orders, the local staggered magnetization distribution due to nonmagnetic impurities in cuprate superconductors is investigated. From this, the net magnetic moment induced by a single or double impurities can be obtained. We show that the net moment induced by a single impurity corresponds to a local spin with S_z=0, or 1/2 depending on the strength of the AF interaction and the impurity scattering. When two impurities are placed at the nearest neighboring sites, the net moment is always zero. For two unitary impurities at the next nearest neighboring sites, and at sites separated by a Cu-ion site, the induced net moment has S_z=0, or 1/2, or 1. The consequence of these results on experiments will be discussed.