扭曲双层石墨烯在准晶-莫尔 crossover 处的电子重构
Electronic Reconstruction at the Quasicrystal-Moiré Crossover in Twisted Bilayer Graphene
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中文总结 AI 辅助
研究发现扭转双层石墨烯在约29°扭转角处发生准晶-莫尔 crossover，层间强杂化使朗道能级简并度随温度从4重变为12重，为研究准周期对称性对低能电子态的调控提供了新平台。
中文摘要 AI 辅助
人们普遍认为，扭曲双层石墨烯的大扭转角在电子层面是平凡的，层间耦合可忽略且无电子重构，这与小扭转角下由莫尔驱动的丰富能带重构及关联物理形成鲜明对比。本文表明，该范式在扭转角约29°附近被打破，此时系统在准晶与公度序之间发生 crossover。原子分辨透射电子显微镜直接揭示了近十二边形准晶对称性与新兴莫尔周期性共存，表明存在一种中间的非周期结构 regime。磁输运测量揭示了由 Umklapp 散射介导的强层间杂化，表现为磁子带间振荡和高度非常规的朗道能级谱。值得注意的是，朗道能级简并度随温度升高从4重演变为12重，这一行为与两个解耦的石墨烯单层不符。这些发现确立了大角度扭曲双层石墨烯作为一个平台，其中准周期对称性从根本上重塑了超越传统莫尔框架的低能电子态。
英文摘要
Large twist angles in twisted bilayer graphene are widely expected to be electronically trivial, with negligible interlayer coupling and no electronic reconstruction, in contrast to the rich moiré-driven band reconstruction and correlated physics that emerge at small twist angles. Here, we show that this paradigm breaks down near a twist angle of 29°, where the system crosses over between quasicrystalline and commensurate order. Atomic-resolution transmission electron microscopy directly reveals the coexistence of near-dodecagonal quasicrystalline symmetry and emerging moiré periodicity, indicating an intermediate, nonperiodic structural regime. Magnetotransport measurements uncover strong interlayer hybridization mediated by Umklapp scattering, manifested by magneto-intersubband oscillations and a highly unconventional Landau-level spectrum. Remarkably, the Landau-level degeneracy evolves from 4- to 12-fold with increasing temperature, a behavior incompatible with two decoupled graphene monolayers. These findings establish large-angle twisted bilayer graphene as a platform where quasiperiodic symmetry fundamentally reshapes low-energy electronic states beyond the conventional moiré framework.
