Floquet-Driven Indirect Exchange Interaction in Magnetically Doped Graphene

We investigate the non-equilibrium indirect exchange interaction in irradiated, magnetically doped two-dimensional election systems. Our theory goes beyond the linear response regime corresponding to the conventional RKKY theory and is non-perturbative in the strengths of both the electron-impurity spin interaction and the driving light field. Using magnetically doped graphene as an example, we focus on the case of strong coupling between magnetic impurities and present analytic and numerical results of the time-averaged exchange coupling as a function of the driving light field and other system parameters. In particular, we discuss the effects of interplay between non-equilibrium Floquet driving and quantum interference effects due to higher-order electron-impurity spin scattering.