Effect of impurity states on the NMR spectra of high-$T_c$ cuprates

TL;DR

This paper investigates how impurity-induced resonance states in high-$T_c$ cuprates influence their magnetic susceptibility and NMR spectra, revealing their effective magnetic moments and explaining experimental observations across doping regimes.

Contribution

It provides a detailed analysis of impurity resonance states' effects on magnetic properties and NMR spectra in high-$T_c$ cuprates, highlighting their role in different doping regimes.

Findings

Resonance states behave like free magnetic moments.

Impurity susceptibility explains NMR spectral features.

Effective moments vary between overdoped and underdoped regimes.

Abstract

A strong nonmagnetic impurity can induce a resonance state in the d-wave superconducting state. As far as magnetic properties are concerned, this resonance state behaves effectively like a free moment. It leads to a Curie-Weiss-like magnetic susceptibility in an intermediate temperature regime below $T_{c}$. From the impurity susceptibility, the effective moment of the resonance state is deduced and compared with experiments. The contribution of the resonance to the magnetic susceptibility can account for the main feature of the NMR spectra in overdoped high-$T_c$ materials. In the underdoped regime, the contribution from the resonance to the magnetic susceptibility is also substantial, but the effective moment of the resonance is smaller than the total moment induced by a nonmagnetic impurity.