Enhanced superconductivity in spin–orbit proximitized bilayer graphene
Abstract
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 superconductivity1. 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 for which the normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal that superconductivity in BLG–WSe₂ can exhibit 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, indicating that proximity-induced (Ising) spin–orbit coupling plays a key role in stabilizing the pairing. Our results pave the way for engineering robust, highly tunable and ultra-clean graphene-based superconductors.
Additional Information
© 2023 Springer Nature. We thank A. Young and A. Macdonald for fruitful discussions. This work has been primarily supported by NSF-CAREER award (no. DMR-1753306), and the Office of Naval Research (grant no. N142112635) and the Army Research Office (grant award no. W911NF17-1-0323). Nanofabrication efforts have been in part supported by the 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 the 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 no. GBMF1250. C.L. and E.L.-H. acknowledge support from the Gordon and Betty Moore Foundation's EPiQS Initiative, grant no. GBMF8682. Contributions. Y.Z. and S.N.-P. designed the experiment. Y.Z., R.P. and H.Z. performed the measurements, fabricated the devices and analysed the data. A.T., E.L.-H. and C.L. developed the theoretical models and performed the calculations supervised by J.A. K.W. and T.T. provided the 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 shown in the main figures are available from the CaltechDATA at https://doi.org/10.22002/wecmz-csm13. Code availability. The code used to reproduce data plots is available from the CaltechDATA at https://doi.org/10.22002/wecmz-csm13. The code used for the modelling is available upon reasonable request. The authors declare no competing interests.Attached Files
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Additional details
- Eprint ID
- 119483
- Resolver ID
- CaltechAUTHORS:20230223-726426000.4
- NSF
- DMR-1753306
- Office of Naval Research (ONR)
- N142112635
- Army Research Office (ARO)
- W911NF17-1-0323
- Department of Energy (DOE)
- DE-SC0019166
- Alfred P. Sloan Foundation
- FG-2020-13716
- Institute for Quantum Information and Matter (IQIM)
- Gordon and Betty Moore Foundation
- GBMF1250
- Gordon and Betty Moore Foundation
- GBMF8682
- Created
-
2023-02-24Created from EPrint's datestamp field
- Updated
-
2023-06-07Created from EPrint's last_modified field
- Caltech groups
- Institute for Quantum Information and Matter, TAPIR, Walter Burke Institute for Theoretical Physics, Kavli Nanoscience Institute