Coupling Stacking Orders with Interlayer Magnetism in Bilayer H-VSe_2

Stacking-dependent magnetism in van der Waals materials has caught intense interests. Based on the first principle calculations, we investigate the coupling between stacking orders and interlayer magnetic orders in bilayer H-VSe_2. It is found that there are two stable stacking orders in bilayer H-VSe_2, named AB-stacking and A^\primeB-stacking. Under standard DFT framework, the A^\primeB-stacking prefers the interlayer AFM order and is semiconductive, whereas the AB-stacking prefers the FM order and is metallic. However, under the DFT+U framework both the stacking orders prefer the interlayer AFM order and are semiconductive. By detailedly analyzing this difference, we find that the interlayer magnetism originates from the competition between antiferromagnetic interlayer super-superexchange and ferromagnetic interlayer double exchange, in which both the interlayer Se-4p_z orbitals play a crucial role. In the DFT+U calculations, the double exchange is suppressed due to the opened bandgap, such that the interlayer magnetic orders are decoupled with the stacking orders. Based on this competition mechanism, we propose that a moderate hole doping can significantly enhance the interlayer double exchange, and can be used to switch the interlayer magnetic orders in bilayer VSe_2. This method is also applicable to a wide range of semiconductive van der Waals magnets.