Quadruple Moiré Pockets in Lateral Heterobilayers: Programmable Phononic Reconfiguration and Anomalous Second Harmonic Generation.

Abstract

Moiré-engineering in 2D transition-metal dichalcogenides offers access to correlated quantum phenomena. However, simultaneous control over twist-angle (θ) and material combinations to tune phonons, excitons, and their collective interactions remains limited. This study presents scalable, quadruple moiré-pockets formed by vertically stacking chemical vapor deposition-grown monolayer MoS₂-WS₂ and MoSe₂-WSe₂ lateral heterostructures with controlled θ (0⁰-60°), within a single flatland. Moiré non-rigidity induces lattice-relaxation via rotational reconstruction (θ<8°) and volumetric dilation (θ>8°), resulting in strain-mediated phonon frequency-softening and linewidth-broadening, respectively. Strain localizes selectively in mechanically softer crystal for θ<8°, while an epitaxial-pseudomorphic pattern dominates for θ>8°. Degree of phonon-reconfiguration and angle-resolved photoemission spectroscopy uncover the role of interfacial orbitals in modulating interlayer coupling. At aligned angles (θ-0° and 60°), specifically, MoS₂ exhibits Davydov splitting and reduced valley polarization, reflecting symmetry breaking and chiral phonon effects. At θ-3°, WS₂/WSe₂ shows up to 480% enhancement in second-harmonic generation (SHG), while WS₂/MoSe₂ records the lowest due to variations in interlayer-coherence and band-offset-driven phase delay. Notably, at θ-60°, only WS₂/MoSe₂ exhibits an anomalous 300% SHG enhancement, attributed to large phase delay and reconstruction-induced strain. Electronic bandstructure calculations support these observations. These findings offer programmable multi-moiré platforms for opto-straintronics, sensing, and on-chip quantum photonics applications.