Ultra-fast control of magnetic relaxation in a periodically driven Hubbard model

Motivated by cold atom and ultra-fast pump-probe experiments we study the melting of long-range antiferromagnetic order of a perfect N\'eel state in a periodically driven repulsive Hubbard model. The dynamics is calculated for a Bethe lattice in infinite dimensions with non-equilibrium dynamical mean-field theory. In the absence of driving melting proceeds differently depending on the quench of the interactions to hopping ratio $U/J_0$ from the atomic limit. For $U \gg J_0$ decay occurs due to mobile charge-excitations transferring energy to the spin sector, while for $J_0 \gtrsim U$ it is governed by the dynamics of residual quasi-particles. Here we explore the rich effects strong periodic driving has on this relaxation process spanning three frequency $\omega$ regimes: (i) high-frequency $\omega \gg U,J_0$, (ii) resonant $l\omega = U > J_0$ with integer $l$, and (iii) in-gap $U > \omega > J_0$ away from resonance. In case (i) we can quickly switch the decay from quasi-particle to charge-excitation mechanism through the suppression of $J_0$. For (ii) the interaction can be engineered, even allowing an effective $U=0$ regime to be reached, giving the reverse switch from a charge-excitation to quasi-particle decay mechanism. For (iii) the exchange interaction can be controlled with little effect on the decay. By combining these regimes we show how periodic driving could be a potential pathway for controlling magnetism in antiferromagnetic materials. Finally, our numerical results demonstrate the accuracy and applicability of matrix product state techniques to the Hamiltonian DMFT impurity problem subjected to strong periodic driving.