Spontaneous Formation of Altermagnetism from Orbital Ordering

TL;DR

This paper demonstrates that altermagnetism, a third type of collinear magnetism with unique spin-splitting properties, can spontaneously emerge from orbital ordering without relying on crystallographic anisotropy, expanding the understanding of magnetic phases.

Contribution

It introduces a microscopic two-orbital model showing that interaction-induced orbital and antiferromagnetic order can generate altermagnetism independently of lattice anisotropy.

Findings

Altermagnetism can arise from electronic interactions without crystallographic anisotropy.

The model predicts measurable spin-splitter conductivity.

Potential material candidates for interaction-induced altermagnetism are discussed.

Abstract

Altermagnetism has emerged as a third type of collinear magnetism. In contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit extra even-parity wave spin order parameters resulting in a spin-splitting of electronic bands in momentum space. In real space, sublattices of opposite spin polarization are anisotropic and related by rotational symmetry. In the hitherto identified altermagnetic candidate materials the anisotropies arise from the local crystallographic symmetry. Here, we show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without the crystallographic sublattice anisotropy. We provide a microscopic example of a two-orbital model showing that the coexistence of staggered antiferromagnetic and orbital order can realize robust altermagnetism. We quantify the spin-splitter conductivity as a key experimental observable and discuss material candidates for the interaction-induced realization of altermagnetism.