Tunable Orbital Ferromagnetism at Noninteger Filling of a Moiré Superlattice

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Abstract

The flat bands resulting from moiré superlattices exhibit fascinating correlated electron phenomena such as correlated insulators, ( Nature 2018, 556 (7699), 80-84), ( Nature Physics 2019, 15 (3), 237) superconductivity, ( Nature 2018, 556 (7699), 43-50), ( Nature 2019, 572 (7768), 215-219) and orbital magnetism. ( Science 2019, 365 (6453), 605-608), ( Nature 2020, 579 (7797), 56-61), ( Science 2020, 367 (6480), 900-903) Such magnetism has been observed only at particular integer multiples of n0, the density corresponding to one electron per moiré superlattice unit cell. Here, we report the experimental observation of ferromagnetism at noninteger filling (NIF) of a flat Chern band in a ABC-TLG/hBN moiré superlattice. This state exhibits prominent ferromagnetic hysteresis behavior with large anomalous Hall resistivity in a broad region of densities centered in the valence miniband at n = -2.3n0. We observe that, not only the magnitude of the anomalous Hall signal, but also the sign of the hysteretic ferromagnetic response can be modulated by tuning the carrier density and displacement field. Rotating the sample in a fixed magnetic field demonstrates that the ferromagnetism is highly anisotropic and likely purely orbital in character.

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Contributors

Guorui Chen: (View ORCID Profile)

Aaron L. Sharpe: (View ORCID Profile)

Bosai Lyu: (View ORCID Profile)

Lili Jiang: (View ORCID Profile)

Hongyuan Li: (View ORCID Profile)

Kenji Watanabe: (View ORCID Profile)

Takashi Taniguchi: (View ORCID Profile)

Michael F. Crommie: (View ORCID Profile)

Zhiwen Shi: (View ORCID Profile)

Journal

Title: Nano Letters

Abbreviated Title: Nano Lett.

Publisher: American Chemical Society (ACS)

ISSN (Print): 1530-6984

ISSN (Electronic): 1530-6992

Publication date Created: January 12 2022

Publication date (Electronic): January 03 2022

Publication date (Print): January 12 2022

Volume: 22

Issue: 1

Pages: 238-245

Affiliations

[1 ]Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States

[2 ]Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China

[3 ]Department of Applied Physics, Stanford University, Stanford, California 94305, United States

[4 ]Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States

[5 ]Quantum and Electronic Materials Department, Sandia National Laboratories, Livermore, California 94550, United States

[6 ]Department of Physics, Stanford University, Stanford, California 94305, United States

[7 ]Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

[8 ]Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

[9 ]International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

[10 ]Kavli Energy NanoSciences Institute, University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

[11 ]Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

[12 ]State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China

[13 ]Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China