# Proximity exchange effects in MoSe$_2$ and WSe$_2$ heterostructures with CrI$_3$: twist angle, layer, and gate dependence

## TL;DR

This study uses first-principles calculations to demonstrate how proximity exchange effects in MoSe2 and WSe2 heterostructures with CrI3 can be controlled by twist angle, layer stacking, and gating, revealing potential for magnetic property tuning in 2D materials.

## Contribution

It reveals that proximity exchange in MoSe2 and WSe2 can be modulated by twist, gate, and layer configuration, and shows the effects are detectable via optical signatures, advancing 2D magnetic heterostructure design.

## Key findings

- Proximity exchange can be tuned by twist angle and gating.
- Antiferromagnetic CrI3 bilayers induce similar exchange effects as ferromagnetic layers.
- Adding an hBN barrier reduces the proximity exchange significantly.

## Abstract

Proximity effects in two-dimensional (2D) van der Waals heterostructures offer controllable ways to tailor the electronic band structure of adjacent materials. Exchange proximity in particular is important for making materials magnetic without hosting magnetic ions. Such synthetic magnets could be used for studying magnetotransport in high-mobility 2D materials, or magneto-optics in highly absorptive nominally nonmagnetic semiconductors. Using first-principles calculations, we show that the proximity exchange in monolayer MoSe$_2$ and WSe$_2$ due to ferromagnetic monolayer CrI$_3$ can be tuned (even qualitatively) by twisting and gating. Remarkably, the proximity exchange remains the same when using antiferromagnetic CrI$_3$ bilayer, paving the way for optical and electrical detection of layered antiferromagnets. Interestingly, the proximity exchange is opposite to the exchange of the adjacent antiferromagnetic layer. Finally, we show that the exchange proximity is confined to the layer adjacent to CrI$_3$, and that adding a separating hBN barrier drastically reduces the proximity effect. We complement our it ab initio results with tight-binding modeling and solve the Bethe-Salpeter equation to provide experimentally verifiable optical signatures (in the exciton spectra) of the proximity exchange effects.