Sunku Sai S, McLeod Alexander S, Stauber Tobias, Yoo Hyobin, Halbertal Dorri, Ni Guangxin, Sternbach Aaron, Jiang Bor-Yuan, Taniguchi Takashi, Watanabe Kenji, Kim Philip, Fogler Michael M, Basov D N
Department of Physics, Columbia University, New York, New York 10027-6902, United States.
Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027-6902, United States.
Nano Lett. 2020 May 13;20(5):2958-2964. doi: 10.1021/acs.nanolett.9b04637. Epub 2020 Apr 3.
We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moiré superlattices in other van der Waals heterostructures.
我们报告了一项对扭曲双层石墨烯（TBG）的纳米光电流与红外纳米显微镜联用研究，该研究能够在短至20纳米的长度尺度上探究局部电子现象。我们表明，光电流在载流子密度处改变符号，追踪TBG的局部超晶格态密度。我们利用这一特性通过局部光热效应识别不同局部扭曲角的区域。与光电流研究一致，红外纳米成像实验揭示了由扭曲角相关的带间跃迁主导的光导率特征。我们的结果提供了一种快速且可靠的方法来绘制TBG的电子结构，并表明类似方法可广泛应用于探测其他范德华异质结构中莫尔超晶格的电子不均匀性。
