Ultra‐Fast Control of Magnetic Relaxation in a Periodically Driven Hubbard Model

• Published in: Annalen der Physik 2017-10, Vol.529 (10), p.n/a
• Main Authors: Mendoza‐Arenas, Juan Jose, Gómez‐Ruiz, Fernando Javier, Eckstein, Martin, Jaksch, Dieter, Clark, Stephen R.
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Charge transfer; Excitation; Floquet theory; Magnetic induction; Magnetic relaxation; Magnetic resonance; Mathematical models; Mean field theory; non‐equilibrium dynamical mean‐field theory; Particle decay; Particle spin; Ultrafast control
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.201700024

Motivated by cold atom and ultra‐fast pump‐probe experiments we study the melting of long‐range antiferromagnetic order of a perfect Néel 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/ν0 from the atomic limit. For U≫ν0 decay occurs due to mobile charge‐excitations transferring energy to the spin sector, while for ν0≳U it is governed by the dynamics of residual quasi‐particles. Here we explore the rich effects that strong periodic driving has on this relaxation process spanning three frequency ω regimes: (i) high‐frequency ω≫U,ν0, (ii) resonant lω=U>ν0 with integer l, and (iii) in‐gap U>ω>ν0 away from resonance. In case (i) we can quickly switch the decay from quasi‐particle to charge‐excitation mechanism through the suppression of ν0. 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. Motivated by state‐of‐the‐art experiments on ultra‐fast control of many‐body quantum systems, the dynamics of a periodically‐driven Hubbard lattice is analyzed in an infinite‐dimensional Bethe geometry. Its evolution from an antiferromagetic state is simulated by combining nonequilibrium DMFT with a MPS impurity solver. Tuning the driving frequency, magnetic melting slowdown (high frequency), enhancement and dynamics reversal (resonance) are induced. Periodic driving thus provides a pathway for manipulating magnetism in complex systems.