Racemic van der Waals Assembly of Planar-Chiral 2D Materials for Intrinsic One-Dimensional Moiré Superlattices

Intrinsic one-dimensional (1D) moiré superlattices provide a state-of-the-art platform for exploring 1D physics. They emerge when one of the two long-range moiré periodicities collapses, which requires a mirror symmetry in the parent 2D materials. Planar-chiral 2D materials such as ReSe2, which lack mirror symmetry, have been excluded from hosting intrinsic 1D moiré superlattices, severely limiting the available material platforms. Here, we propose a racemic van der Waals assembly strategy to overcome this symmetry requirement by compensating the planar chirality through stacking opposite enantiomers, which cannot be achieved by conventional enantiomer-pure assembly. Using the racemic assembly, we fabricated planar-achiral bilayer ReSe2, which was confirmed by circularly polarized Raman spectroscopy, and identified two 1D moiré superlattices near 58 and 61° via transmission electron microscopy. Geometrical analysis identifies six discrete critical twist angles that satisfy the intrinsic 1D condition. Our results establish racemic assembly as a general route to achieve intrinsic 1D moiré superlattices in planar-chiral 2D materials.