Interplay between Interlayer Shift and Twist: Twisted van der Waals Nanowires Driven by Rotational Twinning
In van der Waals(vdW) layered materials, interlayer shift and twist have enabled the control of material properties through polytype and moire engineering. Various approaches, including bottom-up synthesis and manual layer-by-layer stacking, have been utilized to engineer targeted stacking configurations. However, the interplay between interlayer shift and twist, as well as reliable mechanisms for fine-tuning these parameters, remains largely unexplored. Here, we report a previously unrecognized twisting mechanism arising from preferred tilted stacking and twinning in vdW crystals. Electron diffraction and atomic-resolution scanning transmission electron microscopy(STEM) imaging reveal that the lattice planes of group-IV chalcogenide GeSe_{2-x}Te_x rotate continuously along the nanowire growth axis, with twist rates depending systematically on nanowire radius. Atomic-scale imaging further identifies a continuous rotational twin boundary extending along the central region of the nanowire. First-principles calculations and structural relaxation simulations confirm that the twisting deformation originates from energetic competition between the preferred interlayer stacking registry and the strain cost imposed by rotational twinning. These findings establish rotational twinning as an intrinsic route to spontaneous twist formation and provide a design principle for realizing twist-engineered vdW crystals with compatible crystal symmetries and stacking motifs.