Temperature-Induced Magnonic Chern Insulator in Collinear Antiferromagnets

Thermal fluctuation in magnets will bring temperature-dependent self-energy corrections to the magnons, however, their effects on the topological orders of magnons is not well explored. Here we demonstrate that such corrections can induce a Chern insulating phase in two-dimensional collinear antiferromagnets with sublattice asymmetries by increasing temperature. We present the phase diagram of the system and show that the trivial magnon bands at zero temperature exhibit Chern insulating phase above a critical temperature before the paramagnetic phase transition. The self-energy corrections close and reopen the bandgap at {\Gamma} or K points, accompanied by a magnon chirality switch and nontrivial Berry curvature transition. The thermal Hall effect of magnons or detecting the magnon polarization can give experimentally prominent signatures of topological transitions. We include the numerical results based on van der Waals magnet MnPS3, calling for experimental implementation. Our work presents a new paradigm for constructing topological phase that is beyond the linear spin wave theory.