Spectroscopy of a tunable moiré system with a correlated and topological flat band.
Spectroscopy of a tunable moiré system with a correlated and topological flat band.
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DOI：
10.1038/s41467-021-23031-0
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发表时间：
2021-05-12
影响因子：
16.6
通讯作者：
Yazdani A
中科院分区：
文献类型：
--
作者：
Liu X;Chiu CL;Lee JY;Farahi G;Watanabe K;Taniguchi T;Vishwanath A;Yazdani A
由二维晶体扭曲堆叠产生的莫尔超晶格可以容纳具有平坦能量色散的电子带，其中增强的相互作用促进相关电子态。扭曲双层石墨烯（TDBG），其中两个Bernal双层石墨烯以扭曲角堆叠，是具有可调平坦带的莫尔系统。在这里，我们使用门调谐扫描隧道光谱直接证明TDBG的带结构与电场的可调谐性，并显示其平坦带的电子相关性和拓扑结构的光谱特征。我们的光谱实验与TDBG带结构的连续模型一致，并揭示了相关绝缘体间隙在其孤立的平带部分填充的签名。该平坦带的拓扑性质的探讨与应用程序的磁场，这导致谷极化和分裂的陈带与一个大的有效g-因子。扭曲的双层石墨烯具有可以用电场调谐的平坦带。在这里，通过使用门调谐扫描隧道光谱，作者证明了可调谐的平带，并揭示相关电子态的光谱特征和拓扑性质的平带。
Moiré superlattices created by the twisted stacking of two-dimensional crystals can host electronic bands with flat energy dispersion in which enhanced interactions promote correlated electron states. The twisted double bilayer graphene (TDBG), where two Bernal bilayer graphene are stacked with a twist angle, is such a moiré system with tunable flat bands. Here, we use gate-tuned scanning tunneling spectroscopy to directly demonstrate the tunability of the band structure of TDBG with an electric field and to show spectroscopic signatures of electronic correlations and topology for its flat band. Our spectroscopic experiments are in agreement with a continuum model of TDBG band structure and reveal signatures of a correlated insulator gap at partial filling of its isolated flat band. The topological properties of this flat band are probed with the application of a magnetic field, which leads to valley polarization and the splitting of Chern bands with a large effective g-factor. Twisted double bilayer graphene hosts flat bands that can be tuned with an electric field. Here, by using gate-tuned scanning tunneling spectroscopy, the authors demonstrate the tunability of the flat band and reveal spectral signatures of correlated electron states and the topological nature of the flat band.
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