Charge localization, frustration relief, and spin-orbit coupling in U$_3$O$_8$

TL;DR

This study reinterprets neutron scattering data on U$_3$O$_8$, revealing its magnetic order, charge localization effects, and significant spin-orbit coupling influence on electronic properties, providing new insights into its low-temperature behavior.

Contribution

The paper introduces a group theory-based analysis showing magnetic order and charge localization effects in U$_3$O$_8$, highlighting the impact of spin-orbit coupling on its electronic structure.

Findings

Ground state has collinear out-of-plane magnetic moments with antiferromagnetic coupling.

Charge localization relieves geometric frustration, leading to Néel order.

Spin-orbit coupling significantly affects conduction band states and band gap.

Abstract

Research efforts on the low temperature magnetic order and electronic properties of U$_3$O$_8$ have been inconclusive so far. Reinterpreting neutron scattering results, we use group representation theory to show that the ground state presents collinear out-of-plane magnetic moments, with antiferromagnetic coupling both in-layer and between layers. Charge localization relieves the initial geometric frustration, generating a slightly distorted honeycomb sublattice with N\'eel order. We show, furthermore, that spin-orbit coupling has a giant effect on the conduction band states and band gap value. Our results allow a reinterpretation of recent optical absorption measurements.