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Title: Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice

Abstract

Studies of two-dimensional electron systems in a strong magnetic field revealed the quantum Hall effect1, a topological state of matter featuring a finite Chern number C and chiral edge states2,3. Haldane4 later theorized that Chern insulators with integer quantum Hall effects could appear in lattice models with complex hopping parameters even at zero magnetic field. The ABC-trilayer graphene/hexagonal boron nitride (ABC-TLG/hBN) moiré superlattice provides an attractive platform with which to explore Chern insulators because it features nearly flat moiré minibands with a valley-dependent, electrically tunable Chern number5,6. Here we report the experimental observation of a correlated Chern insulator in an ABC-TLG/hBN moiré superlattice. We show that reversing the direction of the applied vertical electric field switches the moiré minibands of ABC-TLG/hBN between zero and finite Chern numbers, as revealed by large changes in magneto-transport behaviour. For topological hole minibands tuned to have a finite Chern number, we focus on quarter filling, corresponding to one hole per moiré unit cell. The Hall resistance is well quantized at h/2e2 (where h is Planck's constant and e is the charge on the electron), which implies C = 2, for a magnetic field exceeding 0.4 tesla. The correlated Chern insulator is ferromagnetic, exhibiting substantial magnetic hysteresismore » and a large anomalous Hall signal at zero magnetic field. Our discovery of a C = 2 Chern insulator at zero magnetic field should open up opportunities for discovering correlated topological states, possibly with topological excitations7, in nearly flat and topologically nontrivial moiré minibands.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [5];  [6];  [1];  [7];  [7];  [6];  [4];  [3];  [8];  [9]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
  2. Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  5. Univ. of California, Berkeley, CA (United States)
  6. Shanghai Jiao Tong Univ. (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing (China)
  7. National Inst. for Materials Science, Tsukuba (Japan)
  8. Collaborative Innovation Center of Advanced Microstructures, Nanjing (China); Fudan Univ., Shanghai (China)
  9. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; National Science Foundation (NSF); Gordon and Betty Moore Foundation; National Key Research Program of China; National Science Foundation of China; Chinese Academy of Sciences; National Natural Science Foundation of China (NNSFC)
OSTI Identifier:
1647087
Alternate Identifier(s):
OSTI ID: 1676375
Grant/Contract Number:  
AC02-76SF00515; GBMF3429; 2016YFA0300703; 2018YFA0305600; U1732274; 11527805; 11425415; 11421404; XDB30000000; 2016YFA0302001; 11574204; 11774224; DMR-1608505; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Volume: 579; Journal Issue: 7797; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
electronic properties and devices; ferromagnetism; topological matter

Citation Formats

Chen, Guorui, Sharpe, Aaron L., Fox, Eli J., Zhang, Ya-Hui, Wang, Shaoxin, Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Shi, Zhiwen, Senthil, T., Goldhaber-Gordon, David, Zhang, Yuanbo, and Wang, Feng. Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice. United States: N. p., 2020. Web. doi:10.1038/s41586-020-2049-7.
Chen, Guorui, Sharpe, Aaron L., Fox, Eli J., Zhang, Ya-Hui, Wang, Shaoxin, Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Shi, Zhiwen, Senthil, T., Goldhaber-Gordon, David, Zhang, Yuanbo, & Wang, Feng. Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice. United States. doi:10.1038/s41586-020-2049-7.
Chen, Guorui, Sharpe, Aaron L., Fox, Eli J., Zhang, Ya-Hui, Wang, Shaoxin, Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Shi, Zhiwen, Senthil, T., Goldhaber-Gordon, David, Zhang, Yuanbo, and Wang, Feng. Wed . "Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice". United States. doi:10.1038/s41586-020-2049-7.
@article{osti_1647087,
title = {Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice},
author = {Chen, Guorui and Sharpe, Aaron L. and Fox, Eli J. and Zhang, Ya-Hui and Wang, Shaoxin and Jiang, Lili and Lyu, Bosai and Li, Hongyuan and Watanabe, Kenji and Taniguchi, Takashi and Shi, Zhiwen and Senthil, T. and Goldhaber-Gordon, David and Zhang, Yuanbo and Wang, Feng},
abstractNote = {Studies of two-dimensional electron systems in a strong magnetic field revealed the quantum Hall effect1, a topological state of matter featuring a finite Chern number C and chiral edge states2,3. Haldane4 later theorized that Chern insulators with integer quantum Hall effects could appear in lattice models with complex hopping parameters even at zero magnetic field. The ABC-trilayer graphene/hexagonal boron nitride (ABC-TLG/hBN) moiré superlattice provides an attractive platform with which to explore Chern insulators because it features nearly flat moiré minibands with a valley-dependent, electrically tunable Chern number5,6. Here we report the experimental observation of a correlated Chern insulator in an ABC-TLG/hBN moiré superlattice. We show that reversing the direction of the applied vertical electric field switches the moiré minibands of ABC-TLG/hBN between zero and finite Chern numbers, as revealed by large changes in magneto-transport behaviour. For topological hole minibands tuned to have a finite Chern number, we focus on quarter filling, corresponding to one hole per moiré unit cell. The Hall resistance is well quantized at h/2e2 (where h is Planck's constant and e is the charge on the electron), which implies C = 2, for a magnetic field exceeding 0.4 tesla. The correlated Chern insulator is ferromagnetic, exhibiting substantial magnetic hysteresis and a large anomalous Hall signal at zero magnetic field. Our discovery of a C = 2 Chern insulator at zero magnetic field should open up opportunities for discovering correlated topological states, possibly with topological excitations7, in nearly flat and topologically nontrivial moiré minibands.},
doi = {10.1038/s41586-020-2049-7},
journal = {Nature (London)},
issn = {0028-0836},
number = 7797,
volume = 579,
place = {United States},
year = {2020},
month = {3}
}

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    Works referencing / citing this record:

    Correlated states in twisted double bilayer graphene
    journal, March 2020