ARPES sensitivity to short-range antiferromagnetic correlations

TL;DR

This paper demonstrates that ARPES can effectively probe short-range antiferromagnetic correlations in Mott insulators, revealing a direct link between spectral weight and spin correlation length, thus expanding ARPES's applicability beyond itinerant systems.

Contribution

It shows that ARPES can detect short-range magnetic correlations in insulating materials, providing a new tool for studying electron-spin interactions in strongly correlated systems.

Findings

Spectral weight beyond the AF zone boundary correlates with spin correlation length.

Significant spectral weight is observed even for short-range correlations.

Temperature dependence of spectral weight scales with spin stiffness.

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is one of most powerful techniques to unravel the electronic properties of layered materials and in the last decades it has lead to a significant progress in the understanding of the band structures of cuprates, pnictides and other materials of current interest. On the other hand, its application to Mott-Hubbard insulating materials where a Fermi surface is absent has been more limited. Here we show that in these latter materials, where electron spins are localized, ARPES may provide significant information on the spin correlations which can be complementary to the one derived from neutron scattering experiments. Sr$_2$Cu$_{1-x}$Zn$_x$O$_2$Cl$_2$, a prototype of diluted spin $S=1/2$ antiferromagnet (AF) on a square lattice, was chosen as a test case and a direct correspondence between the amplitude of the spectral weight beyond the AF zone boundary derived from ARPES and the spin correlation length $\xi$ estimated from $^{35}$Cl NMR established. It was found even for correlation lengths of a few lattice constants a significant spectral weight in the back-bended band is present which depends markedly on $\xi$. Moreover the temperature dependence of that spectral weight is found to scale with the $x$ dependent spin-stiffness. These findings prove that ARPES technique is very sensitive to short-range correlations and its relevance in the understanding of the electronic correlations in cuprates is discussed.