Comment on "Skyrmion Hall Effect in Altermagnets"

Abstract

In their Letter, Jin et al. [Phys. Rev. Lett. 133, 196701 (2024)] predict a transverse velocity $v_y$ for skyrmions driven by spin-transfer torque (STT), known as skyrmion Hall effect (SkHE), in d-wave altermagnets. Usually, the SkHE emerges from the skyrmion's topological charge which here cancels between sublattices. Instead, Jin et al. attribute the SkHE to the dimensionless quadrupole tensor $A_{ij}$. The result in their Eq. (12) is fitted to micromagnetic simulations, yielding a finite value for $A_{xy}$. However, via the divergence theorem, $A_{ij}$ simplifies to a boundary integral that vanishes for a sufficiently smooth and localized texture. In this Comment, we substantiate our claim from Ref. [2] that the numerically observed SkHE by Jin et al. for a micromagnetic model with standard Zhang-Li STT in the individual sublattices is merely a discretization artefact.

Comment on arXiv:2407.03959 [Phys. Rev. Lett. 133, 196701 (2024)], 2 pages, 1 figure