Floquet engineering of exchange interaction in multi-orbital Mott insulators

We consider driving multi-orbital Mott insulators using laser radiation. We derive general expressions for periodically driven spin-orbital models using time-dependent perturbation theory. We show that the effective exchange interactions of the Floquet spin-orbital Hamiltonians are highly tunable by the frequency, amplitude, and polarization of the laser. We also take the effect of finite bandwidth of excitations into account and study possible heating effects. We further apply our formalism to orthorhombic titanates YTiO₃ and LaTiO₃ based on first-principles calculations, and find that the spin exchange interactions in these compounds can be engineered to a large extent by tuning the frequency and electric-field amplitude of the laser.