Twisted moiré bilayers at small twist angles have defined the paradigm for flat bands and correlated topological phases. In this talk, I shift the focus to the less-charted territory of moiré structures formed at large twist angles where commensurability occurs only accidentally at discreate angles. Using twisted WSe₂ as a model system, at 30°, we realize a dodecagonal moiré quasicrystal that lacks translational symmetry. Valley-resolved scanning tunneling spectroscopy visualizes dense quasi-minigaps arising from strong interlayer Umklapp scattering. Moving to the twist angles near but deviate from large commensurate angles (e.g. 21.8˚ and 27.8˚), instead of forming incommensurate moiré structure, the lattice reconstructs into a periodic super-moiré comprising three inequivalent commensurate rotational faults. The resulting zone-folding produces a cascade of minibands, including narrow bands near the valence-band maximum. Together, these results extend moiré physics well beyond the small-angle paradigm and open routes to engineered correlated and topological phases without relying on magic-angle conditions.
*These works are primarily supported by the National Science Foundation (NSF) through the Center for Dynamics and Control of Materials, which is an NSF Materials Research Science and Engineering Center under Cooperative Agreement No. DMR-2308817.
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Publication:[1] Li, Y., Shi, C., Zhang, F., Liu, X., Xue, Y., Ha, V. A., ... & Shih, C. K. (2025). Robust supermoiré pattern in large-angle single-twist bilayers. Nature Physics, 1-8. [2] Li, Y., Zhang, F., Ha, V. A., Lin, Y. C., Dong, C., Gao, Q., ... & Shih, C. K. (2024). Tuning commensurability in twisted van der Waals bilayers. Nature, 625(7995), 494-499. [3] Liu, Z., Gao, Q., Li, Y., Liu, X., Zhang, F., Kim, D. S., ... & Li, X. (2024). Field-Tunable Valley Coupling and Localization in a Dodecagonal Semiconductor Quasicrystal. arXiv preprint arXiv:2408.02176.
