Emerging Ferroelectric Domains: Stacking and Rotational Landscape of MoS₂ Moiré Bilayers.

The structures and properties of moiré patterns in the twisted bilayers of two-dimensional (2D) materials are known to depend sensitively on the twist angle, yet their dependence on the stacking order remains comparatively underexplored. In this study, we use molecular dynamics simulations to systematically investigate the combined effects of the stacking order and rotation in MoS₂ bilayers. Beginning from five well-established high-symmetry bilayer stackings, we apply twist angles between 1° and 120° to the top layer, revealing a variety of relaxed moiré structures. Our results show that the initial stacking significantly influences the moiré domain configurations that emerge at a given twist angle. While all five stacking orders are metastable without twist, they form two moiré-equivalent classes, AA/AB and AA'/A'B/AB', i.e., for a given twist angle, structures within each class relax to the same moiré configuration. Specifically, initial AA and AB stackings give rise to triangular ferroelectric domains near 0 ± 3°, while AA', A'B, and AB' stackings produce triangular ferroelectric domains near 60 ± 3°. At precisely 60° and 120° twists, the bilayers relax into pure high-symmetry stackings, highlighting the rotational relationships between these configurations and explaining the shift of 60° in the ferroelectric rotational range. These findings demonstrate the critical role of the stacking order in governing the rich moiré landscapes accessible in twistronic systems.