Correlation length in cuprates deduced from the impurity-induced magnetization

TL;DR

This paper introduces a novel NMR technique to image impurity-induced magnetization in cuprates, revealing the magnetic correlation length's behavior across different doping levels and its relation to the pseudogap regime.

Contribution

A new multi-nuclei NMR method is developed to measure the impurity-induced magnetization and extract the intrinsic magnetic correlation length in cuprates.

Findings

The impurity-induced polarization extends up to six lattice constants at 80K in underdoped cuprates.

The correlation length follows a Curie law and evolves smoothly through the pseudogap regime.

The correlation length is reduced near optimal doping but retains similar spatial shape.

Abstract

We report a new multi-nuclei based NMR method which allows us to image the staggered polarization induced by nonmagnetic Li impurities in underdoped O6.6 and slightly overdoped O7 YBa2Cu3O6+y above T_C. The spatial extension of the polarization xi_imp approximately follows a Curie law, increasing up to six lattice constants at T=80K at O6.6 in the pseudogap regime. Near optimal doping, the staggered magnetization has the same shape, with xi_imp reduced by a factor 2. xi_imp is argued to reveal the intrinsic magnetic correlation length of the pure system. It is found to display a smooth evolution through the pseudogap regime.