Chiral diffraction from aperiodic monotile structure

Aperiodic systems, such as quasiperiodic structures, exhibit properties distinct from those of periodic structures. In 2023, Smith et al. discovered an aperiodic structure based on a single tile shape that can tessellate the plane only aperiodically, known as an aperiodic monotile. Here, by using this monotile tiling, we propose a quasiperiodic structure which possesses perfect threefold rotational (C3) symmetry but lacks mirror symmetry. Diffraction experiments reveal quasicrystalline properties of the proposed aperiodic structure through observation of clear Bragg peaks and independence of illumination position. Furthermore, we observe chiral properties including pinwheel-like diffraction patterns and unconventional circular-polarization-dependent behavior, which is absent in conventional quasiperiodic structures with mirror symmetry. These findings establish chiral quasiperiodic structures as a platform for studying aperiodic systems beyond traditional quasicrystals, broadening the study of nonperiodic structures. The authors artificially realized an aperiodic monotile structure discovered in 2023 and observed chiral optical diffraction. The results reveal distinctive circular-polarization responses from inversion-asymmetric quasiperiodic order.