Dual Twisted Interfaces Enable Tunable Second Harmonic Generation in Chemical Vapor Deposition Grown Trilayer MoS₂

Twisted bilayer transition metal dichalcogenides, governed by a single twisted interface, offer a versatile platform for manipulating interlayer coupling and emergent optical behavior. However, despite extensive studies on single twisted interface systems, how multi-interface twisted stacking influences nonlinear optical behavior remains unclear. Here, we address this gap by systematically investigating the nonlinear optical performance of chemical vapor deposition (CVD) grown twisted trilayer MoS₂ (TT-MoS₂) with multi-interface twisted stacking. We fabricate all nine distinct trilayer MoS₂ configurations by CVD. Raman and photoluminescence show that twisted interfaces modulate interlayer coupling, giving rise to stacking-dependent phonon and excitonic responses. Atomic-resolution scanning, transmission electron microscopy, and selected area electron diffraction confirm dual twisted interfaces and a supermoiré lattice. Guided by these structural insights, we examine the second harmonic generation (SHG) response across all nine trilayer configurations. Extending the coherent SH field superposition model to a trilayer system with two independent twisted interfaces, we develop a framework that describes how the dual interfaces govern the SHG intensity and polarization orientation across stacking configurations. Our findings establish TT-MoS₂ as a versatile nonlinear platform and open new avenues for understanding and exploiting multi-interface twisted coupling to engineer nonlinear optical responses in van der Waals materials.