Moir\'e-driven multiferroic order in twisted CrCl$_3$, CrBr$_3$ and CrI$_3$ bilayers

TL;DR

This paper demonstrates that twisting bilayers of chromium trihalides induces a moiré-driven multiferroic order with strong magnetoelectric coupling, enabling electric control of magnetic textures like skyrmions.

Contribution

It reveals the emergence of multiferroic order in twisted chromium trihalide bilayers driven by moiré patterns, a phenomenon absent in aligned layers, and highlights the potential for electric control of magnetic textures.

Findings

Moiré patterns induce non-collinear spin textures in twisted bilayers.

Twisted CrBr₃ bilayers exhibit the strongest multiferroic order.

Strong magnetoelectric coupling enables electric control of skyrmions.

Abstract

Layered van der Waals materials have risen as a powerful platform to engineer artificial competing states of matter. Here we show the emergence of multiferroic order in twisted chromium trihalide bilayers, an order fully driven by the moir\'e pattern and absent in aligned multilayers. Using a combination of spin models and ab initio calculations, we show that a spin texture is generated in the moir\'e supercell of the twisted system as a consequence of the competition between stacking-dependent interlayer magnetic exchange and magnetic anisotropy. An electric polarization arises associated with such a non-collinear magnetic state due to the spin-orbit coupling, leading to the emergence of a local ferroelectric order following the moir\'e. Among the stochiometric trihalides, our results show that twisted CrBr$_3$ bilayers give rise to the strongest multiferroic order. We further show the emergence of a strong magnetoelectric coupling, which allows the electric generation and control of magnetic skyrmions. Our results put forward twisted chromium trihalide bilayers, and in particular CrBr$_3$ bilayers, as a powerful platform to engineer artificial multiferroic materials and electrically tunable topological magnetic textures.