Optical detection of 4-spin chiral interaction in a 2D honeycomb ferrimagnet

Abstract

Broken inversion symmetry of magnetic lattice is normally described by Lifshitz invariants in micromagnetic energy functional. Three exceptions are the lattices with T${}_{\text{d}}$, C${}_{\text{3h}}$ and D${}_{\text{3h}}$ point group symmetries. The inversion symmetry breaking of the corresponding magnets is described by more complex 4-spin chiral invariants that cannot be related to Dzyaloshinskii-Moriya interaction. Experimental detection of 4-spin chiral interactions is an important task that has yet to be performed. We propose that the 4-spin chiral interaction can be probed by energy selective magnon relaxation in two-dimensional ferromagnet Fe${}_3$GeTe${}_2$ that possess D${}_{\text{3h}}$ point group symmetry.