Light-induced magnetic phase transition in van der Waals antiferromagnets

Control over magnetic properties by optical stimulation is not only interesting from the physics point of view, but also important for practical applications such as magneto-optical devices. Here, based on a simple tight-binding (TB) model, we propose a general theory of light-induced magnetic phase transition (MPT) in antiferromagnets. Considering the fact that the bandgap of the antiferromagnetic (AFM) phase is usually larger than that of the ferromagnetic (FM) one for a given system, we suggest that light-induced electronic excitation prefers to stabilize the FM state over the AFM one, and will induce an MPT from AFM phase to FM phase once a critical photocarrier concentration (alpha(c)) is reached. This theory has been confirmed by performing first-principles calculations on a series of 2D van der Waals (vdW) antiferromagnets. Interestingly, a linear relationship between alpha(c) and the intrinsic material parameters is obtained, in agreement with our TB model analysis. Our general theory paves a new way to manipulate 2D magnetism with high speed and superior resolution.