Current-driven nonlinear skyrmion dynamics in altermagnets

TL;DR

This paper investigates current-driven skyrmion dynamics in frustrated altermagnets, revealing unanticipated helicity rotation behaviors and potential applications in THz technology and frequency combs.

Contribution

It uncovers the unidirectional helicity rotation independent of the Hall angle and demonstrates the generation of magnon frequency combs in altermagnets.

Findings

Helicity unidirectionally rotates with current density squared.

Helicity rotation velocity is highly anisotropic.

Helicity oscillations occur in the terahertz regime.

Abstract

The center of mass and helicity are two dynamic degrees of freedom of skyrmions. In this work, we study the current-driven skyrmion motion in frustrated altermagnets. Contrary to conventional wisdom, we find that the skyrmion helicity is not locked with the skyrmion Hall angle, but unidirectionally rotates with a global angular velocity proportional to the square of the current density. In addition, we find that the helicity rotation velocity is highly anisotropic, depending on the direction of current flows. We also observe helicity oscillation in the terahertz regimes, where the nonlinear mixing between the fast and slow modes generates a magnon frequency comb. Full atomistic spin dynamics simulations verify our theoretical predictions. Our results establish frustrated altermagnets as a promising platform for skyrmionics, THz technology, and frequency comb.