Weak-Coupling Theory of Neutron Scattering as a Probe of Altermagnetism

TL;DR

This paper introduces a theoretical framework using a Hubbard model to study altermagnetism and predicts unique neutron scattering signatures that can identify this new magnetic phase.

Contribution

It presents a minimal Hubbard model with anisotropy to describe altermagnetism and predicts its distinctive neutron scattering response.

Findings

Altermagnetic state evolves from metallic to insulating with increasing Coulomb interaction.

Magnetic excitation spectrum depends on chirality along certain reciprocal space directions.

Neutron scattering can potentially detect altermagnetism through its unique spectral features.

Abstract

Inelastic neutron scattering provides a powerful probe of the magnetic excitations of quantum magnets. Altermagnets have recently emerged as a new class of magnets with vanishing net magnetization characteristic of antiferromagnets and with a spin-split electronic structure typical of ferromagnets. Here we introduce a minimal Hubbard model with two-sublattice orthorhombic anisotropy as a framework to study altermagnetism. Using unrestricted Hartree-Fock calculations, we find an altermagnetic state for this model that evolves from a metallic state to an insulating state with increasing Hubbard-$U$ Coulomb repulsion. We then examine the inelastic neutron scattering response in these states using random-phase approximation calculations of the dynamic spin susceptibility $\chi''({\bf q}, \omega)$. We find that the magnetic excitation spectrum depends on its chirality for ${\bf q}$ along certain directions in reciprocal space, an observation that may be used in inelastic neutron scattering experiments as a probe of altermagnetism.