Li Geng, Krishna Kumar Roshan, Stepanov Petr, Pantaleón Pierre A, Zhan Zhen, Agarwal Hitesh, Bercher Adrien, Barrier Julien, Watanabe Kenji, Taniguchi Takashi, Kuzmenko Alexey B, Guinea Francisco, Torre Iacopo, Koppens Frank H L
ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Av. Carl Friedrich Gauss 3, Castelldefels, Barcelona 08860, Spain.
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain.
Nano Lett. 2024 Dec 18;24(50):15956-15963. doi: 10.1021/acs.nanolett.4c02853. Epub 2024 Dec 5.
Twisted bilayer graphene (TBG) represents a highly tunable, strongly correlated electron system. However, understanding the single-particle band structure alone has been challenging due to a lack of spectroscopic measurements over a broad energy range. Here, we probe the band structure of TBG around the magic angle using infrared spectroscopy and reveal spectral features that originate from interband transitions. In combination with quantum transport, we connect spectral features over a broad energy range (10-700 meV) and track their evolution with the twist angle. We compare our data with calculations of the band structures obtained via the continuum model and find good agreement only when considering a variation of interlayer/intralayer tunneling parameters with the twist angle. Our analysis suggests that the magic angle also shifts due to lattice relaxation and is better defined for a wide angular range of 0.9-1.1°. Additionally, our measurements offer an optical fingerprint of the magic angle for screening heterostructures before nanofabrication.
扭曲双层石墨烯（TBG）是一种高度可调谐的强关联电子系统。然而，由于缺乏在宽能量范围内的光谱测量，仅理解单粒子能带结构一直具有挑战性。在这里，我们使用红外光谱探测了魔角附近的TBG能带结构，并揭示了源于带间跃迁的光谱特征。结合量子输运，我们在宽能量范围（10 - 700毫电子伏特）内连接光谱特征，并追踪它们随扭曲角的演变。我们将我们的数据与通过连续模型获得的能带结构计算结果进行比较，发现只有在考虑层间/层内隧穿参数随扭曲角变化时才具有良好的一致性。我们的分析表明，由于晶格弛豫，魔角也会发生移动，并且在0.9 - 1.1°的宽角度范围内能更好地定义。此外，我们的测量为在纳米制造之前筛选异质结构提供了魔角的光学指纹。
