# Anapole Correlations in Sr2IrO4 Defy the jeff = 1/2 Model

## TL;DR

This paper reveals that the magnetic neutron diffraction data for Sr2IrO4 contradicts the widely accepted jeff = 1/2 model, highlighting complex anapole correlations that challenge existing theoretical assumptions.

## Contribution

It demonstrates that anapole correlations in Sr2IrO4 violate the jeff = 1/2 model, providing new insights into the material's electronic and magnetic entanglement.

## Key findings

- Anapole correlations in Sr2IrO4 are incompatible with the jeff = 1/2 model.
- Neutron diffraction reveals entangled electronic degrees of freedom.
- Magnetic symmetry and quantum mechanics enforce specific diffraction properties.

## Abstract

Zel'dovich (spin) anapole correlations in Sr2IrO4 unveiled by magnetic neutron diffraction contravene the spin-orbit coupled ground state used by the jeff = 1/2 (pseudo-spin) model. Specifically, spin and space know inextricable knots which bind each to the other in the iridate. The diffraction property studied in the Letter is enforced by strict requirements from quantum mechanics and magnetic symmetry. It has not been exploited in the past, whereas neutron diffraction by anapole moments is established. Entanglement of the electronic degrees of freedom is captured by binary correlations of the anapole and position operators, and hallmarked in the diffraction amplitude by axial atomic multipoles with an even rank.

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Source: https://tomesphere.com/paper/1905.05535