Symmetry Engineering of van der Waals magnetic VCl₃ monolayer

The discovery of 2D van der Waals magnetic monolayers attracted tremendous interest due to their stacking-dependent magnetism. Further breaking their spatial symmetry leads to more exotic properties including possible multiferroicity and Morie physics. In this talk, I will introduce our recent progress in symmetry engineering of semiconducting magnetic monolayer VCl₃ via the van der Waals interface. Using molecular beam epitaxy, we achieved controllable growth of high-quality monolayer (ML) VCl₃ on different van der Waals substrates. We first discuss the ML-VCl₃/NbSe₂ heterojunction, in which the commensurate NbSe₂ substrate breaks both rotational and inversion symmetries of VCl3. Combined with scanning tunneling microscopy, first-principle calculation, and magnetization measurement, we show evidence of coexisting in-plane ferroelectricity and antiferromagnetism in the ML-VCl₃. Next, ML-VCl₃ on epitaxy graphene/SiC substrate is discussed. We demonstrate the creation of unexpected electronic superlattice potential in ML-VCl₃. Substrate SiC reconstruction plays a key role in creating the superlattice, which induces a periodic strain and therefore breaks the translation symmetry in ML-VCl₃. Our work shows V-based trihalides as a promising platform for realizing both multiferroic order and Morie-related correlation phenomena.