Electronic and Magnonic Properties of $g$-Wave Altermagnetism in Intercalated Transition Metal Dichalcogenides

TL;DR

This study investigates the electronic and magnetic properties of intercalated transition-metal dichalcogenides as altermagnetic materials, revealing how bond anisotropy and spin orientation influence spin splitting and magnon behavior.

Contribution

It demonstrates the origin of $g$-wave spin splitting and magnon chiral splitting in specific materials using first-principles and effective models, highlighting their potential as altermagnetic platforms.

Findings

Bond-dependent hopping anisotropy causes $g$-wave electronic spin splitting.

Chiral magnon splitting depends on spin orientation and single-ion anisotropy.

Magnon-magnon interactions preserve symmetry and reduce splitting magnitude.

Abstract

Altermagnetism is a recently identified class of magnetic order characterized by unconventional momentum-dependent spin splitting in the absence of net magnetization, and understanding its electronic and magnetic properties is essential for revealing its fundamental physics and potential applications. In this work we investigate two intercalated transition-metal dichalcogenides, Fe$_{1/4}$NbS$_2$ and V$_{1/3}$NbS$_2$, as candidate altermagnetic materials by using effective tight-binding and spin models complemented by first-principles calculations. We show that the $g$-wave electronic spin splitting originates from bond-dependent hopping anisotropy, leading to material-dependent nodal structures. For the magnetic excitations, the emergence of chiral splitting in the magnon dispersion is controlled by single-ion anisotropy, which manifests as altermagnetic-like nodal structures when spins are oriented along an easy-axis. Conversely, this altermagnetic signature disappears when the spins are aligned in an easy-plane. Beyond linear spin-wave theory, we find that $1/S$ corrections from magnon--magnon interactions preserve the symmetry and nodal structure of the band splitting while generally reducing its magnitude, with strong antiferromagnetic exchange leading to a non-negligible renormalization of the chiral splitting. Our findings establish intercalated transition-metal dichalcogenides as promising platforms for understanding the interplay between crystal symmetry, non-relativistic spin splitting, and magnetic properties in altermagnets.