Floquet engineering of Mott insulators with strong spin-orbit coupling

TL;DR

This paper introduces a method to control exchange interactions in Mott insulators with strong spin-orbit coupling using circularly polarized light, enabling tuning of magnetic properties in materials like $ ext{RuCl}_3$.

Contribution

It derives an effective Hamiltonian for multiorbital systems under light irradiation and demonstrates how to manipulate exchange interactions, including the possibility of suppressing the Heisenberg term.

Findings

Magnitudes and signs of $J$, $K$, and $\Gamma$ can be simultaneously tuned.

The Heisenberg interaction $J$ can be minimized relative to anisotropic exchanges.

The method applies to models relevant for $ ext{RuCl}_3$ and similar materials.

Abstract

We propose a method for controlling the exchange interactions of Mott insulators with strong spin-orbit coupling. We consider a multiorbital system with strong spin-orbit coupling and a circularly polarized light field and derive its effective Hamiltonian in the strong-interaction limit. Applying this theory to a minimal model of $\alpha$-RuCl$_{3}$, we show that the magnitudes and signs of three exchange interactions, $J$, $K$, and $\Gamma$, can be changed simultaneously. Then, considering another case in which one of the hopping integrals has a different value and the other parameters are the same as those for $\alpha$-RuCl$_{3}$, we show that the Heisenberg interaction $J$ can be made much smaller than the anisotropic exchange interactions $K$ and $\Gamma$.