Ferromagnetism in tilted fermionic Mott insulators

We investigate the magnetism of tilted fermionic Mott insulators. With a small tilt, the fermions are almost localized and still form a Mott-insulating state, where the localized spins interact with each other via antiferromagnetic exchange coupling modified by the tilt [1,2]. A large tilt, rather than destroying localization, induces the Wannier-Stark localization and the fermions can still be regarded as a localized spin system. The sign of the exchange coupling can be changed to realize ferromagnetic interaction. We show these behaviors via both perturbation theory and real-time numerical simulation for the fermionic Hubbard chain. Our simulation shows that it is possible to effectively control the speed and time-direction of the real-time dynamics with the tilt.

[1] K. Takasan and M. Sato, Phys. Rev. B 100, 060408 (2019).

[2] S. C. Furuya, K. Takasan, and M. Sato, Phys. Rev. Research 3, 033066 (2021).