Chin. Phys. Lett.  2021, Vol. 38 Issue (4): 047301    DOI: 10.1088/0256-307X/38/4/047301
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES |
Emergence of Chern Insulating States in Non-Magic Angle Twisted Bilayer Graphene
Cheng Shen1,2, Jianghua Ying1,2, Le Liu1,2, Jianpeng Liu3,4, Na Li1,2,6, Shuopei Wang1,2,6, Jian Tang1,2, Yanchong Zhao1,2, Yanbang Chu1,2, Kenji Watanabe7, Takashi Taniguchi8, Rong Yang1,5,6, Dongxia Shi1,2,5, Fanming Qu1,2,6, Li Lu1,2,6, Wei Yang1,2,6*, and Guangyu Zhang1,2,5,6*
1Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
3School of Physical Sciences and Technology, ShanghaiTech University, Shanghai 200031, China
4ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 200031, China
5Beijing Key Laboratory for Nanomaterials and Nanodevices, Beijing 100190, China
6Songshan-Lake Materials Laboratory, Dongguan 523808, China
7Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
8International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
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Cheng Shen, Jianghua Ying, Le Liu et al  2021 Chin. Phys. Lett. 38 047301
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Abstract Twisting two layers into a magic angle (MA) of $\sim$$1.1^{\circ}$ is found essential to create low energy flat bands and the resulting correlated insulating, superconducting, and magnetic phases in twisted bilayer graphene (TBG). While most of previous works focus on revealing these emergent states in MA-TBG, a study of the twist angle dependence, which helps to map an evolution of these phases, is yet less explored. Here, we report a magneto-transport study on one non-magic angle TBG device, whose twist angle $\theta$ changes from 1.25$^{\circ}$ at one end to 1.43$^{\circ}$ at the other. For $\theta =1.25^{\circ}$ we observe an emergence of topological insulating states at hole side with a sequence of Chern number $\left| C \right|=4-\left| v \right|$, where $v$ is the number of electrons (holes) in moiré unite cell. When $\theta >1.25^{\circ}$, the Chern insulator from flat band disappears and evolves into fractal Hofstadter butterfly quantum Hall insulator where magnetic flux in one moiré unite cell matters. Our observations will stimulate further theoretical and experimental investigations on the relationship between electron interactions and non-trivial band topology.
Received: 11 February 2021      Published: 17 March 2021
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http://cpl.iphy.ac.cn/10.1088/0256-307X/38/4/047301       OR      http://cpl.iphy.ac.cn/Y2021/V38/I4/047301
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Cheng Shen
Jianghua Ying
Le Liu
Jianpeng Liu
Na Li
Shuopei Wang
Jian Tang
Yanchong Zhao
Yanbang Chu
Kenji Watanabe
Takashi Taniguchi
Rong Yang
Dongxia Shi
Fanming Qu
Li Lu
Wei Yang
and Guangyu Zhang
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