Spectroscopic Visualization of Flat Bands in Magic-Angle Twisted Monolayer-Bilayer Graphene: Coexistence of Localization and Delocalization,Physical Review Letters

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Spectroscopic Visualization of Flat Bands in Magic-Angle Twisted Monolayer-Bilayer Graphene: Coexistence of Localization and Delocalization
Physical Review Letters ( IF 8.1 ) Pub Date : 2022-03-22 , DOI: 10.1103/physrevlett.128.126401
Ling-Hui Tong ₁ , Qingjun Tong ₁ , Li-Zhen Yang ₁ , Yue-Ying Zhou ₁ , Qilong Wu ₁ , Yuan Tian ₁ , Li Zhang ₁ , Lijie Zhang ₁ , Zhihui Qin ₁ , Long-Jing Yin ₁

Affiliation

Recent transport studies have demonstrated the great potential of twisted monolayer-bilayer graphene (TMBG) as a new platform to host moiré flat bands with a higher tunability than twisted bilayer graphene (TBG). However, a direct visualization of the flat bands in TMBG and its comparison with the ones in TBG remain unexplored. Here, via fabricating on a single sample with exactly the same twist angle of

\sim 1.1 3 °

, we present a direct comparative study between TMBG and TBG using scanning tunneling microscopy and spectroscopy. We observe a sharp density of states peak near the Fermi energy in tunneling spectroscopy, confirming unambiguously the existence of flat electronic bands in TMBG. The bandwidth of this flat-band peak is found to be slightly narrower than that of the TBG, validating previous theoretical predictions. Remarkably, by measuring spatially resolved spectroscopy, combined with continuum model calculation, we show that the flat-band states in TMBG exhibit a unique layer-resolved localization-delocalization coexisting feature, which offers an unprecedented possibility to utilize their cooperation on exploring novel correlation phenomena. Our work provides important microscopic insight of flat-band states for better understanding the emergent physics in graphene moiré systems.

中文翻译：

魔角扭曲单层-双层石墨烯平带的光谱可视化：局域化和离域化共存

最近的传输研究表明，扭曲的单层-双层石墨烯 (TMBG) 具有巨大的潜力，可作为承载比扭曲双层石墨烯 (TBG) 更高可调性的莫尔平面带的新平台。然而，TMBG 中平坦带的直接可视化及其与 TBG 中的平坦带的比较仍未探索。在这里，通过在具有完全相同的扭曲角的单个样品上制造

～ 1.1 3 °

，我们使用扫描隧道显微镜和光谱学对 TMBG 和 TBG 进行了直接比较研究。我们在隧道光谱中观察到在费米能量附近有一个尖锐的态密度峰，明确地证实了 TMBG 中平坦电子能带的存在。发现这个平带峰的带宽比 TBG 的带宽略窄，验证了之前的理论预测。值得注意的是，通过测量空间分辨光谱，结合连续介质模型计算，我们表明 TMBG 中的平带态表现出独特的层分辨定位-离域共存特征，这为利用它们的合作探索新的相关现象提供了前所未有的可能性.

更新日期：2022-03-22

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