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Superconductivity in twisted double bilayer graphene stabilized by WSe2

Abstract

Identifying the essential components of superconductivity in graphene-based systems remains a critical problem in two-dimensional materials research. This field is connected to the mysteries that underpin investigations of unconventional superconductivity in condensed-matter physics. Superconductivity has been observed in magic-angle twisted stacks of monolayer graphene but conspicuously not in twisted stacks of bilayer graphene, although both systems host topological flat bands and symmetry-broken states. Here we report the discovery of superconductivity in twisted double bilayer graphene (TDBG) in proximity to WSe2. Samples with twist angles 1.24° and 1.37° superconduct in small pockets of the gate-tuned phase diagram within the valence and conduction band, respectively. Superconductivity emerges from unpolarized phases near van Hove singularities and next to regions with broken isospin symmetry. Our results show the correlation between a high density of states and the emergence of superconductivity in TDBG while revealing a possible role for isospin fluctuations in the pairing.

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Fig. 1: Device characterization.
Fig. 2: Signatures of superconductivity.
Fig. 3: Metrics of superconductivity in D1.
Fig. 4: Van Hove singularities and isospin-polarized phases.

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Data availability

Source data are provided with this paper. All other data are available from the corresponding author upon reasonable request.

Code availability

Codes used for data analysis in this study are also available from the corresponding author upon reasonable request.

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Acknowledgements

We thank A. MacDonald, J. Zhu, N. Wei, S. D. Sarma, Y.-Z. Chou, A. Potter and M. Franz for fruitful discussions. M.K. acknowledges a postdoctoral research fellowship from the Stewart Blusson Quantum Matter Institute (SBQMI). Experiments at the University of British Columbia were undertaken with support from SBQMI, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the Canadian Institute for Advanced Research and the Canada First Research Excellence Fund, Quantum Materials and Future Technologies Program (J.F.). Growing the hBN crystals received support from the Japan Society for the Promotion of Science (KAKENHI grant nos. 19H05790, 20H00354 and 21H05233) to K.W. and T.T.

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R.S. fabricated the devices, with help from M.K. R.S. performed the measurements. R.S., M.K. and J.F. interpreted the data and wrote the paper. J.F. supervised the experiment. K.W. and T.T. provided the hBN crystals.

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Correspondence to Joshua Folk.

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Nature Materials thanks Guangyu Zhang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Sections A–L, each containing a multi-panel figure and discussion in the figure caption.

Source data

Source Data Fig. 1

Experimental data for Fig. 1.

Source Data Fig. 2

Experimental data for Fig. 2.

Source Data Fig. 3

Experimental data for Fig. 3.

Source Data Fig. 4

Experimental data for Fig. 4.

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Su, R., Kuiri, M., Watanabe, K. et al. Superconductivity in twisted double bilayer graphene stabilized by WSe2. Nat. Mater. 22, 1332–1337 (2023). https://doi.org/10.1038/s41563-023-01653-7

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