An anisotropic van der Waals dielectric for symmetry engineering in functionalized heterointerfaces

Van der Waals dielectrics are fundamental materials for condensed matter physics and advanced electronic applications. Most dielectrics host isotropic structures in crystalline or amorphous forms, and only a few studies have considered the role of anisotropic crystal symmetry in dielectrics as a delicate way to tune electronic properties of channel materials. Here, we demonstrate a layered anisotropic dielectric, SiP₂, with non-symmorphic twofold-rotational C₂ symmetry as a gate medium which can break the original threefold-rotational C₃ symmetry of MoS₂ to achieve unexpected linearly-polarized photoluminescence and anisotropic second harmonic generation at SiP₂/MoS₂ interfaces. In contrast to the isotropic behavior of pristine MoS₂, a large conductance anisotropy with an anisotropy index up to 1000 can be achieved and modulated in SiP₂-gated MoS₂ transistors. Theoretical calculations reveal that the anisotropic moiré potential at such interfaces is responsible for the giant anisotropic conductance and optical response. Our results provide a strategy for generating exotic functionalities at dielectric/semiconductor interfaces via symmetry engineering.