Dual-modulation strategy for inducing optical anisotropy in 2D WS₂/CrOCl heterostructures

The intrinsic in-plane isotropy of high-symmetry two-dimensional (2D) transition metal dichalcogenides (TMDs) limits their applicability in polarization-sensitive optoelectronic devices. Conventional strategies such as heterointerface and strain engineering can break rotational symmetry and induce anisotropy, yet they suffer from lattice-matching constraints and limited strain tunability. Here, we present a dual-modulation approach that integrates bilayer WS₂ with the anisotropic van der Waals crystal CrOCl and applies externally engineered hole-induced stress. The in-plane lattice anisotropy of CrOCl induces interfacial symmetry breaking in WS₂, while hole geometry generates controllable stress gradients. This synergy yields a pronounced optical anisotropy, with excitonic linear polarization reaching up to 59%. Furthermore, external magnetic fields can effectively modulate exciton anisotropy, whereas the anisotropy remains stable across various temperatures. First-principles calculations reveal that interfacial charge redistribution, induced by lattice distortion, underlies the observed optical anisotropy. Our results demonstrate a multi-field tuning platform—mechanical, magnetic, and thermal—for tailoring anisotropic light-matter interactions in 2D semiconductors, advancing the development of next-generation directional optoelectronic and quantum devices.