Pure One-Dimensional Moiré Superlattice in Racemate-Stacked Bilayer ReSe₂ With Large Twist Angle

One-dimensional moiré structures, where atoms align periodically along a single direction, represent a new class of moiré patterns distinct from conventional low-angle, two-dimensional lattices. Such patterns have been proposed in low-symmetry materials like WTe₂, black phosphorus and PdSe₂, but their formation typically requires intrinsic mirror planes, limiting material candidates.

Here, we introduce racemate stacking as a new conceptual framework to generate one-dimensional moiré structures in low-symmetry two-dimensional materials that lack intrinsic mirror symmetry, such as ReSe₂. In this approach, we stack two monolayer-ReSe₂ sheets of opposite chirality—what we term racemate stacking—thereby effectively introducing a mirror plane that enables the formation of one-dimensional moiré patterns. We demonstrated this principle experimentally by observing stripe-like moiré superlattices in racemate-stacked ReSe₂ using scanning transmission electron microscopy (STEM) and conductive atomic force microscopy (c-AFM).

This framework highlights the stripe patterns observed in large-angle bilayers are a natural consequence of symmetry and geometric constraints, rather than accidental features. Our results establish racemate stacking as a powerful strategy for creating one-dimensional moiré patterns in low-symmetry two-dimensional materials, opening new opportunities for exploring their unconventional electronic properties.