Floquet theory of spin dynamics under circularly polarized light pulses

Within the Floquet theory of periodically driven quantum systems, the nonlinear single-spin dynamics under pulse of a circularly polarized electromagnetic field is analyzed. It is demonstrated that the field, first, lifts the spin degeneracy and, second, the field-induced spin splitting is accompanied by the photon emission at the spitting frequency. This two-stage process leads, particularly, to the polarization of spins along angular momentum of the circularly polarized field. As a result, the pulse-induced magnetization appears, what can be observed in state-of the-art measurements.