Laser-induced magnetization curve

We propose an all optical ultrafast method to highly magnetize general quantum magnets using a circularly polarized terahertz laser. The key idea is to utilize a circularly polarized laser and its chirping. Through this method, one can obtain magnetization curves of a broad class of quantum magnets as a function of time even without any static magnetic field. We numerically demonstrate the laser-induced magnetization process in realistic quantum spin models and find a condition for the realization. The onset of magnetization can be described by a many-body version of Landau-Zener mechanism. In a particular model, we show that a plateau state with topological properties can be realized dynamically.