Twist-Programmable Exciton Polarization through Dual Anisotropic Proximity in CrOCl/WSe2/CrOCl Heterostructures

Abstract Polarization control in atomically thin semiconductors enables optical information to be encoded beyond intensity and energy. In group-VI transition metal dichalcogenides (TMDs), however, the high in-plane lattice symmetry suppresses excitonic linear polarization, and symmetry breaking from a single van der Waals interface typically provides only weak, weakly programmable anisotropy. Here we create a dual-interface anisotropic proximity platform by sandwiching monolayer WSe2 between two low-symmetry antiferromagnetic CrOCl crystals with controlled relative orientation. When the CrOCl crystallographic axes are nearly aligned, the two interfaces act cooperatively and enhance the degree of linear polarization of WSe2 excitons by a factor of 4–6 relative to single-interface structures. Rotating the CrOCl axes drives a continuous evolution from constructive enhancement to near cancellation, following a cosine-like dependence captured by a Stokes-vector superposition model. An out-of-plane magnetic field further reconfigures the anisotropy through the antiferromagnetic-to-ferrimagnetic transition of CrOCl, yielding a nonmonotonic polarization response. First-principles calculations show that the dual interface strengthens charge redistribution and amplifies W–Se bond distortion by approximately 3-fold. These results establish multi-interface anisotropy engineering as a programmable strategy for controlling exciton polarization in van der Waals semiconductors.