Moiré-driven multiferroic order in twisted CrCl₃, CrBr₃ and CrI₃ bilayers

Layered van der Waals materials are one of the most promising platforms to engineer novel states of matter. In particular, the twist angle that can be imposed between layers has revolutionized the artificial design of materials, by driving different symmetry-breaking orders.

In this talk, we will theoretically demonstrate the emergence of a multiferroic order in twisted chromium trihalide CrX₃ (X=Cl, Br, and I) bilayers using a combination of spin models and ab initio calculations [1]. First, we show that a spin texture arises in the moiré supercell of the twisted system as a consequence of the site-dependent interlayer magnetic exchange created by the moiré. Associated with that non-collinear magnetic state, an electric polarization emerges due to the spin-orbit coupling of the ligand atoms. In particular, we found that CrBr₃ displays the strongest multiferroic order among the stoichiometric compounds. Strong magnetoelectric coupling is found in this system, allowing electric generation and control of magnetic skyrmions.