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Superconductivity in metallic twisted bilayer graphene stabilized by WSe₂

Arora, Harpreet Singh and Polski, Robert and Zhang, Yiran and Thomson, Alex and Choi, Youngjoon and Kim, Hyunjin and Lin, Zhong and Wilson, Ilham Zaky and Xu, Xiaodong and Chu, Jiun-Haw and Watanabe, Kenji and Taniguchi, Takashi and Alicea, Jason and Nadj-Perge, Stevan (2020) Superconductivity in metallic twisted bilayer graphene stabilized by WSe₂. Nature, 583 (7816). pp. 379-384. ISSN 0028-0836. https://resolver.caltech.edu/CaltechAUTHORS:20200225-102617489

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[img] PDF (Supplementary Methods - includes the continuum model details used in Fig. 4 and Extended Data Fig. 10, and Landau level diagram derivations used in Extended Data Fig. 9) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 1: Fabrication details) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 2: Optical images of devices D1–D4) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 3: Additional temperature data for device D1 (0.97°)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 4: Additional data for device D3 (1.04°)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 5: Additional data for device D2 (0.83° contacts)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 6: Additional data from device D1 (0.97°)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 7: Additional data for device D4 (0.80°)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 8 Weak antilocalization data measured in D4 (θ = 0.80°)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 9: Theoretical Landau-level spectrum) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 10: SOI dependence of the band structure) - Supplemental Material
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Abstract

Magic-angle twisted bilayer graphene (TBG), with rotational misalignment close to 1.1 degrees, features isolated flat electronic bands that host a rich phase diagram of correlated insulating, superconducting, ferromagnetic and topological phases. Correlated insulators and superconductivity have been previously observed only for angles within 0.1 degree of the magic angle and occur in adjacent or overlapping electron-density ranges; nevertheless, the origins of these states and the relation between them remain unclear, owing to their sensitivity to microscopic details. Beyond twist angle and strain, the dependence of the TBG phase diagram on the alignment and thickness of the insulating hexagonal boron nitride (hBN) used to encapsulate the graphene sheets indicates the importance of the microscopic dielectric environment. Here we show that adding an insulating tungsten diselenide (WSe₂) monolayer between the hBN and the TBG stabilizes superconductivity at twist angles much smaller than the magic angle. For the smallest twist angle of 0.79 degrees, superconductivity is still observed despite the TBG exhibiting metallic behaviour across the whole range of electron densities. Finite-magnetic-field measurements further reveal weak antilocalization signatures as well as breaking of fourfold spin–valley symmetry, consistent with spin–orbit coupling induced in the TBG via its proximity to WSe₂. Our results constrain theoretical explanations for the emergence of superconductivity in TBG and open up avenues towards engineering quantum phases in moiré systems.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1038/s41586-020-2473-8DOIArticle
https://rdcu.be/b5DvFPublisherFree ReadCube access
https://arxiv.org/abs/2002.03003arXivDiscussion Paper
ORCID:
AuthorORCID
Arora, Harpreet Singh0000-0002-7674-735X
Polski, Robert0000-0003-0887-8099
Zhang, Yiran0000-0002-8477-0074
Thomson, Alex0000-0002-9938-5048
Kim, Hyunjin0000-0001-9886-0487
Watanabe, Kenji0000-0003-3701-8119
Alicea, Jason0000-0001-9979-3423
Nadj-Perge, Stevan0000-0002-2916-360X
Alternate Title:Superconductivity in metallic twisted bilayer graphene stabilized by monolayer WSe₂, Superconductivity in metallic twisted bilayer graphene stabilized by monolayer WSe2, Superconductivity in metallic twisted bilayer graphene stabilized by WSe₂, Superconductivity in metallic twisted bilayer graphene stabilized by WSe2, Superconductivity without insulating states in twisted bilayer graphene stabilized by monolayer WSe₂, Superconductivity without insulating states in twisted bilayer graphene stabilized by monolayer WSe2
Additional Information:© 2020 Springer Nature Limited. Received 31 January 2020. Accepted 21 May 2020. Published 15 July 2020. We acknowledge discussions with H. Ren, D. Zhong, Y. Peng, G. Refael, F. von Oppen, Y. Saito, A. Young, D. Efetov, J. Eisenstein and P. Lee. The device nanofabrication was performed at the Kavli Nanoscience Institute (KNI) at Caltech. This work was supported by the National Science Foundation through programme CAREER DMR-1753306 and grant DMR-1723367, the Gist–Caltech memorandum of understanding and the Army Research Office under grant award W911NF-17-1-0323. Nanofabrication performed by Y.Z. was supported by the US Department of Energy DOE-QIS programme (DE-SC0019166). J.A. and S.N.-P. also acknowledge the support of IQIM (an NSF-funded Physics Frontiers Center). A.T. and J.A. are grateful for support from the Walter Burke Institute for Theoretical Physics at Caltech and the Gordon and Betty Moore Foundation’s EPiQS Initiative, grant GBMF8682. The material synthesis at the University of Washington was supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the DOE, Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443 and the Gordon and Betty Moore Foundation’s EPiQS Initiative, grant GBMF6759 to J.-H.C. These authors contributed equally: Harpreet Singh Arora, Robert Polski, Yiran Zhang. Author Contributions: H.S.A., R.P., Y.Z. and S.N.-P. designed the experiment. H.S.A. made the TBG–WSe2 devices assisted by Y.Z., H.K. and Y.C. H.S.A. and R.P. performed the measurements. Y.Z. made and measured initial TBG devices and D4. H.S.A., R.P. and S.N.-P. analysed the data. A.T. and J.A. developed the continuum model that includes spin–orbit interactions and performed model calculations. Z.L., I.Z.W., X.X. and J.-H.C. provided WSe2 crystals. K.W. and T.T. provided hBN crystals. H.S.A., R.P., Y.Z., A.T., J.A. and S.N.-P. wrote the manuscript with input from other authors. S.N.-P. supervised the project. Data availability: The data that support the findings of this study are available from the corresponding authors on reasonable request. The authors declare no competing interests. Peer review information: Nature thanks Ronny Thomale and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Group:Institute for Quantum Information and Matter, Kavli Nanoscience Institute, Walter Burke Institute for Theoretical Physics
Funders:
Funding AgencyGrant Number
NSFDMR-1753306
NSFDMR-1723367
GIST-Caltech Research CollaborationUNSPECIFIED
Army Research Office (ARO)W911NF-17-1-0323
Department of Energy (DOE)DE-SC0019166
Institute for Quantum Information and Matter (IQIM)UNSPECIFIED
NSF Physics Frontiers CenterUNSPECIFIED
Walter Burke Institute for Theoretical Physics, CaltechUNSPECIFIED
Gordon and Betty Moore FoundationGBMF8682
Department of Energy (DOE)DE-SC0019443
Gordon and Betty Moore FoundationGBMF6759
Issue or Number:7816
Record Number:CaltechAUTHORS:20200225-102617489
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200225-102617489
Official Citation:Arora, H.S., Polski, R., Zhang, Y. et al. Superconductivity in metallic twisted bilayer graphene stabilized by WSe2. Nature 583, 379–384 (2020). https://doi.org/10.1038/s41586-020-2473-8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101531
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Feb 2020 18:51
Last Modified:15 Jul 2020 22:05

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