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
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.
收稿日期: 2021-02-11
出版日期: 2021-03-17
引用本文:
. [J]. 中国物理快报, 2021, 38(4): 47301-047301.
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. Emergence of Chern Insulating States in Non-Magic Angle Twisted Bilayer Graphene. Chin. Phys. Lett., 2021, 38(4): 47301-047301.
Cao Y, Fatemi V, Demir A, Fang S, Tomarken S L, Luo J Y, Sanchez-Yamagishi J D, Watanabe K, Taniguchi T, Kaxiras E, Ashoori R C and Jarillo-Herrero P 2018 Nature556 80
[3]
Cao Y, Fatemi V, Fang S, Watanabe K, Taniguchi T, Kaxiras E and Jarillo-Herrero P 2018 Nature556 43
[4]
Yankowitz M, Chen S, Polshyn H, Zhang Y, Watanabe K, Taniguchi T, Graf D, Young A F and Dean C R 2019 Science363 1059
[5]
Lu X, Stepanov P, Yang W, Xie M, Aamir M A, Das I, Urgell C, Watanabe K, Taniguchi T, Zhang G, Bachtold A, MacDonald A H and Efetov D K 2019 Nature574 653
[6]
Choi Y, Kemmer J, Peng Y, Thomson A, Arora H, Polski R, Zhang Y, Ren H, Alicea J, Refael G, Oppen F V, Watanabe K, Taniguchi T and Nadj-Perge S 2019 Nat. Phys.15 1174
[7]
Kerelsky A, McGilly L J, Kennes D M, Xian L, Yankowitz M, Chen S, Watanabe K, Taniguchi T, Hone J, Dean C, Rubio A and Pasupathy A N 2019 Nature572 95
[8]
Xie Y, Lian B, Jäck B, Liu X, Chiu C L, Watanabe K, Taniguchi T, Bernevig B A and Yazdani A 2019 Nature572 101
[9]
Jiang Y, Lai X, Watanabe K, Taniguchi T, Haule K, Mao J and Andrei E Y 2019 Nature573 91
Sharpe A L, Fox E J, Barnard A W, Finney J, Watanabe K, Taniguchi T, Kastner M A and Goldhaber-Gordon D 2019 Science365 605
[12]
Serlin M, Tschirhart C L, Polshyn H, Zhang Y, Zhu J, Watanabe K, Taniguchi T, Balents L and Young A F 2020 Science367 900
[13]
Cao Y, Luo J Y, Fatemi V, Fang S, Sanchez-Yamagishi J D, Watanabe K, Taniguchi T, Kaxiras E and Jarillo-Herrero P 2016 Phys. Rev. Lett.117 116804
[14]
Kim K, DaSilvab A, Huangc S, Fallahazada B, Larentisa S, Taniguchid T, Watanabe K, LeRoyc B J, MacDonald A H and Tutuc E 2017 Proc. Natl. Acad. Sci. USA114 3364
[15]
Polshyn H, Zhu J, Kumar M A, Zhang Y, Yang F, Tschirhart C L, Serlin M, Watanabe K, Taniguchi T, MacDonald A H and Young A F 2020 arXiv:2004.11353v1
[16]
Chen S, He M, Zhang Y H, Hsieh V, Fei Z, Watanabe K, Taniguchi T, Cobden D H, Xu X, Dean C R and Yankowitz M 2020 arXiv:2004.11340v1
[17]
Chen G, Sharpe A L, Fox E J, Zhang Y H, Wang S, Jiang L, Lyu B, Li H, Watanabe K, Taniguchi T, Shi Z, Senthil T, Goldhaber-Gordon D, Zhang Y and Wang F 2020 Nature579 56
Dean C R, Wang L, Maher P, Forsythe C, Ghahari F, Gao Y, Katoch J, Ishigami M, Moon P, Koshino M, Taniguchi T, Watanabe K, Shepard K L, Hone J and Kim P 2013 Nature497 598
[25]
Ponomarenko L A, Gorbachev R V, Yu G L, Elias D C, Jalil R, Patel A A, Mishchenko A, Mayorov A S, Woods C R, Wallbank J R, Mucha-Kruczynski M, Piot B A, Potemski M, Grigorieva I V, Novoselov K S, Guinea F, Fal'ko V I and Geim A K 2013 Nature497 594
[26]
Hunt B, Sanchez-Yamagishi J D, Young A F, Yankowitz M, LeRoy B J, Watanabe K, Taniguchi T, Moon P, Koshino M, Jarillo-Herrero P and Ashoori R C 2013 Science340 1427
[27]
Yu G L, Gorbachev R V, Tu J S, Kretinin A V, Cao Y, Jalil R, Withers F, Ponomarenko L A, Piot B A, Potemski M, Elias D C, Chen X, Watanabe K, Taniguchi T, Grigorieva I V, Novoselov K S, Fal'ko V I, Geim A K and Mishchenko A 2014 Nat. Phys.10 525
[28]
Yang W, Lu X, Chen G, Wu S, Xie G, Cheng M, Wang D, Yang R, Shi D, Watanabe K, Taniguchi T, Voisin C, Plaçais B, Zhang Y and Zhang G 2016 Nano Lett.16 2387
[29]
Choi Y, Kim H, Peng Y, Thomson A, Lewandowski C, Polski R, Zhang Y, Arora H S, Watanabe K, Taniguchi T, Alicea J and Nadj-Perge S 2020 arXiv:2008.11746
[30]
Park J M, Cao Y, Watanabe K, Taniguchi T and Jarillo-Herrero P 2020 arXiv:2008.12296
Kumar R K, Chen X, Auton G H, Mishchenko A, Bandurin D A, Morozov S V, Cao Y, Khestanova E, Shalom M B, Kretinin A V, Novoselov K S, Eaves L, Grigorieva I V, Ponomarenko L A, Fal'ko V I and Geim A K 2017 Science357 181
2021, Vol. 38 
