Skyrmion Hall effect in altermagnets

TL;DR

This paper predicts a skyrmion Hall effect in altermagnets with zero net magnetization, driven by a hidden gauge field from magnetic quadrupoles, revealing new physics for neutral quasiparticles.

Contribution

It introduces the concept of a skyrmion Hall effect in altermagnets with zero charge, driven by magnetic quadrupoles and a hidden gauge field, expanding understanding of topological effects in magnetic materials.

Findings

Skyrmion Hall effect predicted in zero-net-magnetization altermagnets.

Sign change of Hall angle when swapping exchange couplings.

Skyrmion velocity and Hall angle depend on current direction.

Abstract

It is widely believed that the skyrmion Hall effect is absent in antiferromagnets because of the vanishing topological charge. However, the Aharonov-Casher theory indicates the possibility of topological effects for neutral particles. In this work, we predict the skyrmion Hall effect in emerging altermagnets with zero net magnetization and zero skyrmion charge. We first show that the neutral skyrmion manifests as a magnetic quadrupole in altermagnets. We reveal a hidden gauge field from the magnetic quadrupole, which induces the skyrmion Hall effect when driven by spin transfer torque. Interestingly, we identify a sign change of the Hall angle when one swaps the anisotropic exchange couplings in altermagnets. Furthermore, we demonstrate that both the velocity and Hall angle of altermagnetic skyrmions sensitively depend on the current direction. Our findings real the critical role of magnetic quadrupole in driving the skyrmion Hall effect with vanishing charge, and pave the way to discovering new Hall effect of neutral quasiparticles beyond magnetic skyrmions.