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Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene

Zhang, Yiran and Polski, Robert and Thomson, Alex and Lantagne-Hurtubise, Étienne and Lewandowski, Cyprian and Zhou, Haoxin and Watanabe, Kenji and Taniguchi, Takashi and Alicea, Jason and Nadj-Perge, Stevan (2022) Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene. . (Unpublished)

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In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases as well as magnetic-field-induced superconductivity. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature T꜀ ≈ 30~mK. Here, we show that placing monolayer tungsten diselenide (WSe₂) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in T꜀, and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe₂ as a function of electric field and doping, we establish that superconductivity emerges throughout a region whose normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal a striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe₂ -- suggesting that proximity-induced (Ising) spin-orbit coupling plays a key role in enhancing the pairing. Our results pave the way for engineering robust, highly tunable, and ultra-clean graphene-based superconductors.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Zhang, Yiran0000-0002-8477-0074
Polski, Robert0000-0003-0887-8099
Thomson, Alex0000-0002-9938-5048
Lantagne-Hurtubise, Étienne0000-0003-0417-6452
Lewandowski, Cyprian0000-0002-6944-9805
Zhou, Haoxin0000-0003-1235-0035
Watanabe, Kenji0000-0003-3701-8119
Taniguchi, Takashi0000-0002-1467-3105
Alicea, Jason0000-0001-9979-3423
Nadj-Perge, Stevan0000-0002-2916-360X
Additional Information:Attribution 4.0 International (CC BY 4.0). We thank Andrea Young and Allan Macdonald for fruitful discussions. This work has been primarily supported by NSF-CAREER award (DMR-1753306), and Office of Naval Research (grant no. N142112635), and Army Research Office under Grant Award W911NF17-1-0323. Nanofabrication efforts have been in part supported by Department of Energy DOE-QIS program (DE-SC0019166). S.N-P. acknowledges support from the Sloan Foundation (grant no. FG-2020-13716). J.A. and S.N.-P. also acknowledge support of the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation through Grant GBMF1250. C.L. and E.L.H. acknowledge support from the Gordon and Betty Moore Foundation’s EPiQS Initiative, grant GBMF8682. Author Contribution: Y.Z. and S.N.-P. designed the experiment. Y.Z., R.P. and H.Z. performed the measurements, fabricated the devices, and analyzed the data. A.T., E.L.-H. and C.L. developed theoretical models and performed calculations supervised by J.A. K.W. and T.T. provided hBN crystals. S.N.-P. supervised the project. Y.Z., A.T., E.L.-H., C.L., H.Z., R.P., J.A., and S.N.-P. wrote the manuscript with the input of other authors. Data availability: The data supporting the findings of this study are available from the corresponding authors on reasonable request. Code availability: All code used in modeling in this study is available from the corresponding authors on reasonable request. The authors declare no competing interests.
Group:Institute for Quantum Information and Matter
Funding AgencyGrant Number
Office of Naval Research (ONR)N142112635
Army Research Office (ARO)W911NF17-1-0323
Department of Energy (DOE)DE-SC0019166
Alfred P. Sloan FoundationFG-2020-13716
Institute for Quantum Information and Matter (IQIM)UNSPECIFIED
Gordon and Betty Moore FoundationGBMF1250
Gordon and Betty Moore FoundationGBMF8682
Record Number:CaltechAUTHORS:20220524-180301852
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114895
Deposited By: George Porter
Deposited On:24 May 2022 20:47
Last Modified:24 May 2022 20:47

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