Signatures of quartic asymmetric exchange in a class of two-dimensional magnets

The indirect quartic interaction of spins is suggested to play an important role in two-dimensional magnets with trigonal prismatic symmetry such as an Fe3GeTe2 monolayer and many transition metal dichalcogenides. The proposed interaction is described by terms in micromagnetic energy that are linear in magnetization gradients. Such terms enable the stability of noncollinear magnetic textures. We investigate signatures of the quartic interaction in magnon spectra in the presence of anisotropy and an external magnetic field. We also show how magnetic spirals, which are induced by the proposed interaction, can be manipulated by an external field. Our analysis is based on symmetry considerations and can be used to quantify the quartic interaction strength in experiments with magnetic monolayers.