Disorder effects in the quantum kagome antiferromagnet ZnCu3(OH)6Cl2

TL;DR

This study uses exact diagonalization to analyze how non-magnetic defects influence the magnetic properties of the kagome antiferromagnet ZnCu3(OH)6Cl2, aligning with recent NMR findings and questioning the existence of a spin gap.

Contribution

It provides a parameter-free theoretical analysis of defect effects in the kagome lattice, supporting experimental defect interpretations and highlighting disorder's role at low temperatures.

Findings

Good agreement with NMR data

Defects influence magnetic behavior at low temperatures

Disorder effects challenge the spin gap hypothesis

Abstract

The recent NMR experiments on ZnCu3(OH)6Cl2 motivate our study of the effect of non- magnetic defects on the antiferromagnetic spin-1/2 kagome lattice. We use exact diagonalization methods to study the effect of two such defects on finite size systems. Our results, obtained without adjustable parameters, are in good quantitative agreement with recent Oxygen 17 NMR data. They provide support for the experimental interpretation of the presence of defects within the kagome layers due to Zn/Cu substitutions. Our results also show that disorder effects become relevant at lower temperatures, raising questions about the experimental evidence for the absence of an intrinsic spin gap in the kagome 2D layers.