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Title: Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene

Abstract

When two sheets of graphene are stacked at a small twist angle, the resulting flat superlattice minibands are expected to strongly enhance electron-electron interactions. Here, we present evidence that near three-quarters ( 3 4 ) filling of the conduction miniband, these enhanced interactions drive the twisted bilayer graphene into a ferromagnetic state. In a narrow density range around an apparent insulating state at 3 4 , we observe emergent ferromagnetic hysteresis, with a giant anomalous Hall (AH) effect as large as 10.4 kilohms and indications of chiral edge states. Notably, the magnetization of the sample can be reversed by applying a small direct current. Although the AH resistance is not quantized, and dissipation is present, our measurements suggest that the system may be an incipient Chern insulator.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [3]; ORCiD logo [4];  [4]; ORCiD logo [5]; ORCiD logo [2]
  1. Stanford Univ., CA (United States). Dept. of Applied Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States). Dept. of Physics
  3. Stanford Univ., CA (United States). Dept. of Physics
  4. National Inst. for Materials Science, Tsukuba (Japan)
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States). Dept. of Physics; Science Philanthropy Alliance, Palo Alto, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE
OSTI Identifier:
1548254
Alternate Identifier(s):
OSTI ID: 1545527
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Published Article
Journal Name:
Science
Additional Journal Information:
Journal Volume: 365; Journal Issue: 6453; Journal ID: ISSN 0036-8075
Publisher:
AAAS
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE

Citation Formats

Sharpe, Aaron L., Fox, Eli J., Barnard, Arthur W., Finney, Joe, Watanabe, Kenji, Taniguchi, Takashi, Kastner, M. A., and Goldhaber-Gordon, David. Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. United States: N. p., 2019. Web. doi:10.1126/science.aaw3780.
Sharpe, Aaron L., Fox, Eli J., Barnard, Arthur W., Finney, Joe, Watanabe, Kenji, Taniguchi, Takashi, Kastner, M. A., & Goldhaber-Gordon, David. Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. United States. doi:10.1126/science.aaw3780.
Sharpe, Aaron L., Fox, Eli J., Barnard, Arthur W., Finney, Joe, Watanabe, Kenji, Taniguchi, Takashi, Kastner, M. A., and Goldhaber-Gordon, David. Thu . "Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene". United States. doi:10.1126/science.aaw3780.
@article{osti_1548254,
title = {Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene},
author = {Sharpe, Aaron L. and Fox, Eli J. and Barnard, Arthur W. and Finney, Joe and Watanabe, Kenji and Taniguchi, Takashi and Kastner, M. A. and Goldhaber-Gordon, David},
abstractNote = {When two sheets of graphene are stacked at a small twist angle, the resulting flat superlattice minibands are expected to strongly enhance electron-electron interactions. Here, we present evidence that near three-quarters ( 3 4 ) filling of the conduction miniband, these enhanced interactions drive the twisted bilayer graphene into a ferromagnetic state. In a narrow density range around an apparent insulating state at 3 4 , we observe emergent ferromagnetic hysteresis, with a giant anomalous Hall (AH) effect as large as 10.4 kilohms and indications of chiral edge states. Notably, the magnetization of the sample can be reversed by applying a small direct current. Although the AH resistance is not quantized, and dissipation is present, our measurements suggest that the system may be an incipient Chern insulator.},
doi = {10.1126/science.aaw3780},
journal = {Science},
number = 6453,
volume = 365,
place = {United States},
year = {2019},
month = {7}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1126/science.aaw3780

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