  Dynamic manipulation of magnetism in topological materials is demonstrated
here via a Floquet engineering approach using circularly polarized light.
Increasing the strength of the laser field, besides the expected topological
phase transition, the magnetically doped topological insulator thin film also
undergoes a magnetic phase transition from ferromagnetism to paramagnetism,
whose critical behavior strongly depends on the quantum quenching. In sharp
contrast to the equilibrium case, the non-equilibrium Curie temperatures vary
for different time scale and experimental setup, not all relying on change of
topology. Our discoveries deepen the understanding of the relationship between
topology and magnetism in the non-equilibrium regime and extend optoelectronic
device applications to topological materials.
