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Tunable Sample-Wide Electronic Kagome Lattice in Low-Angle Twisted Bilayer Graphene
Physical Review Letters ( IF 8.1 ) Pub Date : 2022-08-11 , DOI: 10.1103/physrevlett.129.076803
Qi Zheng 1 , Chen-Yue Hao 1 , Xiao-Feng Zhou 1 , Ya-Xin Zhao 1 , Jia-Qi He 1 , Lin He 1
Affiliation  

Overlaying two graphene layers with a small twist angle θ can create a moiré superlattice to realize exotic phenomena that are entirely absent in a graphene monolayer. A representative example is the predicted formation of localized pseudo-Landau levels (PLLs) with kagome lattice in tiny-angle twisted bilayer graphene (TBG) with θ<0.3° when the graphene layers are subjected to different electrostatic potentials. However, this was shown only for the model of rigidly rotated TBG, which is not realized in reality due to an interfacial structural reconstruction. It is believed that the interfacial structural reconstruction strongly inhibits the formation of the PLLs. Here, we systematically study electronic properties of the TBG with 0.075°θ<1.2° and demonstrate, unexpectedly, that the PLLs are quite robust for all the studied TBG. The structural reconstruction suppresses the formation of the emergent kagome lattice in the tiny-angle TBG. However, for the TBG around the magic angle, the sample-wide electronic kagome lattices with tunable lattice constants are directly imaged by using a scanning tunneling microscope. Our observations open a new direction to explore exotic correlated phases in moiré systems.

中文翻译:

低角度扭曲双层石墨烯中的可调谐样品范围电子 Kagome 晶格

以小扭转角覆盖两个石墨烯层θ可以创建莫尔超晶格来实现石墨烯单层中完全不存在的奇异现象。一个具有代表性的例子是在小角度扭曲双层石墨烯 (TBG) 中预测形成具有 kagome 晶格的局部伪朗道能级 (PLL)θ<0.3°当石墨烯层受到不同的静电势时。然而,这仅针对刚性旋转的 TBG 模型显示,由于界面结构重建,这在现实中并未实现。相信界面结构重建强烈抑制PLL的形成。在这里,我们系统地研究了 TBG 的电子特性0.075°θ<1.2°并且出乎意料地证明,对于所有研究的 TBG,PLL 都非常稳健。结构重建抑制了小角TBG中涌现的kagome晶格的形成。然而,对于魔角附近的TBG,具有可调晶格常数的样品范围的电子kagome晶格是通过使用扫描隧道显微镜直接成像的。我们的观察为探索莫尔系统中奇异的相关相开辟了一个新方向。
更新日期:2022-08-11
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