Coarsening of chiral domains in a triangular Heisenberg antiferromagnet

We study the relaxation dynamics of a classical triangular Heisenberg antiferromagnet with an additional four-spin exchange interaction, a model relevant to nuclear magnetism in solid 3He layers. When the four-spin interaction dominates, a novel spin configuration with scalar chiral order emerges. While long-range tetrahedral spin order is destroyed by thermal fluctuations in two dimensions, the chiral order, arising from the breaking of a discrete Ising symmetry, remains stable at finite temperatures. Previous work indeed confirmed that the chiral transition belongs to the 2D Ising universality class. Using a large-scale Landau–Lifshitz–Gilbert dynamics method to simulate a thermal quench of the magnets; however, we find that the coarsening of chiral domains deviates from the Allen–Cahn growth law expected for a non-conserved Ising order parameter. This anomaly appears to be linked to the unusual domain morphology, which retains a mixture of smooth and straight interfaces even at late times.