---
_id: '10025'
abstract:
- lang: eng
text: Ferromagnetism is most common in transition metal compounds but may also arise
in low-density two-dimensional electron systems, with signatures observed in silicon,
III-V semiconductor systems, and graphene moiré heterostructures. Here we show
that gate-tuned van Hove singularities in rhombohedral trilayer graphene drive
the spontaneous ferromagnetic polarization of the electron system into one or
more spin- and valley flavors. Using capacitance measurements on graphite-gated
van der Waals heterostructures, we find a cascade of density- and electronic displacement
field tuned phase transitions marked by negative electronic compressibility. The
transitions define the boundaries between phases where quantum oscillations have
either four-fold, two-fold, or one-fold degeneracy, associated with a spin and
valley degenerate normal metal, spin-polarized `half-metal', and spin and valley
polarized `quarter metal', respectively. For electron doping, the salient features
are well captured by a phenomenological Stoner model with a valley-anisotropic
Hund's coupling, likely arising from interactions at the lattice scale. For hole
filling, we observe a richer phase diagram featuring a delicate interplay of broken
symmetries and transitions in the Fermi surface topology. Finally, by rotational
alignment of a hexagonal boron nitride substrate to induce a moiré superlattice,
we find that the superlattice perturbs the preexisting isospin order only weakly,
leaving the basic phase diagram intact while catalyzing the formation of topologically
nontrivial gapped states whenever itinerant half- or quarter metal states occur
at half- or quarter superlattice band filling. Our results show that rhombohedral
trilayer graphene is an ideal platform for well-controlled tests of many-body
theory and reveal magnetism in moiré materials to be fundamentally itinerant in
nature.
acknowledgement: "The authors acknowledge discussions with A. Macdonald, L. Fu, F.
Wang and M. Zaletel. AFY acknowledges support of the National Science Foundation
under DMR1654186, and the Gordon and Betty Moore Foundation under award GBMF9471.
The authors acknowledge the use of the research facilities within the California
NanoSystems Institute, supported by the University of California, Santa Barbara
and the University of California, Office of the President.\r\nK.W. and T.T. acknowledge
support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant
Number JPMXP0112101001 and JSPS KAKENHI, Grant Number JP20H00354. EB and TH were
supported by the European Research Council (ERC) under grant HQMAT (Grant Agreement
No. 817799). A.G. acknowledges support by the European Unions Horizon 2020 research
and innovation program under the Marie Sklodowska-Curie Grant Agreement\r\nNo. 754411.\r\n"
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Haoxin
full_name: Zhou, Haoxin
last_name: Zhou
- first_name: Tian
full_name: Xie, Tian
last_name: Xie
- first_name: Areg
full_name: Ghazaryan, Areg
id: 4AF46FD6-F248-11E8-B48F-1D18A9856A87
last_name: Ghazaryan
orcid: 0000-0001-9666-3543
- first_name: Tobias
full_name: Holder, Tobias
last_name: Holder
- first_name: James R.
full_name: Ehrets, James R.
last_name: Ehrets
- first_name: Eric M.
full_name: Spanton, Eric M.
last_name: Spanton
- first_name: Takashi
full_name: Taniguchi, Takashi
last_name: Taniguchi
- first_name: Kenji
full_name: Watanabe, Kenji
last_name: Watanabe
- first_name: Erez
full_name: Berg, Erez
last_name: Berg
- first_name: Maksym
full_name: Serbyn, Maksym
id: 47809E7E-F248-11E8-B48F-1D18A9856A87
last_name: Serbyn
orcid: 0000-0002-2399-5827
- first_name: Andrea F.
full_name: Young, Andrea F.
last_name: Young
citation:
ama: Zhou H, Xie T, Ghazaryan A, et al. Half and quarter metals in rhombohedral
trilayer graphene. Nature. 2021. doi:10.1038/s41586-021-03938-w
apa: Zhou, H., Xie, T., Ghazaryan, A., Holder, T., Ehrets, J. R., Spanton, E. M.,
… Young, A. F. (2021). Half and quarter metals in rhombohedral trilayer graphene.
Nature. Springer Nature. https://doi.org/10.1038/s41586-021-03938-w
chicago: Zhou, Haoxin, Tian Xie, Areg Ghazaryan, Tobias Holder, James R. Ehrets,
Eric M. Spanton, Takashi Taniguchi, et al. “Half and Quarter Metals in Rhombohedral
Trilayer Graphene.” Nature. Springer Nature, 2021. https://doi.org/10.1038/s41586-021-03938-w.
ieee: H. Zhou et al., “Half and quarter metals in rhombohedral trilayer graphene,”
Nature. Springer Nature, 2021.
ista: Zhou H, Xie T, Ghazaryan A, Holder T, Ehrets JR, Spanton EM, Taniguchi T,
Watanabe K, Berg E, Serbyn M, Young AF. 2021. Half and quarter metals in rhombohedral
trilayer graphene. Nature.
mla: Zhou, Haoxin, et al. “Half and Quarter Metals in Rhombohedral Trilayer Graphene.”
Nature, Springer Nature, 2021, doi:10.1038/s41586-021-03938-w.
short: H. Zhou, T. Xie, A. Ghazaryan, T. Holder, J.R. Ehrets, E.M. Spanton, T. Taniguchi,
K. Watanabe, E. Berg, M. Serbyn, A.F. Young, Nature (2021).
date_created: 2021-09-19T22:01:25Z
date_published: 2021-09-01T00:00:00Z
date_updated: 2025-04-14T07:43:46Z
day: '01'
department:
- _id: MaSe
- _id: MiLe
doi: 10.1038/s41586-021-03938-w
ec_funded: 1
external_id:
arxiv:
- '2104.00653'
isi:
- '000706977400002'
isi: 1
keyword:
- condensed matter - mesoscale and nanoscale physics
- condensed matter - strongly correlated electrons
- multidisciplinary
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/2104.00653
month: '09'
oa: 1
oa_version: Preprint
project:
- _id: 260C2330-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '754411'
name: ISTplus - Postdoctoral Fellowships
publication: Nature
publication_identifier:
eissn:
- 1476-4687
issn:
- 0028-0836
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
link:
- relation: erratum
url: https://doi.org/10.1038/s41586-021-04181-z
scopus_import: '1'
status: public
title: Half and quarter metals in rhombohedral trilayer graphene
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
year: '2021'
...