Moir\'e skyrmions and chiral magnetic phases in twisted CrX$_{3}$ (X $=$ I, Br, Cl) bilayers

TL;DR

This paper develops a comprehensive theory of magnetic phases in twisted bilayer Cr-trihalides, revealing how stacking and twist angles lead to diverse noncollinear magnetic states, including skyrmion crystals.

Contribution

It introduces a novel theoretical framework combining first-principles calculations and atomistic simulations to predict magnetic phases in twisted CrX$_{3}$ bilayers, including skyrmion formations.

Findings

Skyrmion crystal phases can be stabilized at small twist angles.

Stacking-dependent interlayer exchange creates a moiré field with ferromagnetic and antiferromagnetic patches.

Noncollinear magnetic phases observed align with recent experimental findings.

Abstract

We present a comprehensive theory of the magnetic phases in twisted bilayer Cr-trihalides through a combination of first-principles calculations and atomistic simulations. We show that the stacking-dependent interlayer exchange leads to an effective moir\'e field that is mostly ferromagnetic with antiferromagnetic patches. A wide range of noncollinear magnetic phases can be stabilized as a function of the twist angle and Dzyaloshinskii-Moriya interaction as a result of the competing interlayer antiferromagnetic coupling and the energy cost for forming domain walls. In particular, we demonstrate that for small twist angles various skyrmion crystal phases can be stabilized in both CrI$_3$ and CrBr$_3$. Our results provide an interpretation for the recent observation of noncollinear magnetic phases in twisted bilayer CrI$_3$ and demonstrate the possibility of engineering further nontrivial magnetic ground states in twisted bilayer Cr-trihalides.