Séminaire IQ/RQMP : Étienne Lantagne-Hurtubise

Enhanced superconductivity in spin-orbit proximitized Bernalbilayer graphene

Crystalline graphenemultilayers present a promising platform to explore correlated electronicphenomena in an ultra-clean setting free of the inhomogeneities ubiquitous inmoiré systems. For instance, Bernal-stacked bilayer graphene (BLG) in a strongperpendicular electric field exhibits several symmetry-broken metallic phasesand a fragile, magnetic-field induced superconducting phase with a criticaltemperature Tc ~ 30 mK [1]. I will first discuss the experimental discovery [2]that placing monolayer WSe₂ on BLG promotes Cooper pairing to an extraordinary degree:superconductivity appears at zero magnetic field with an order-of-magnitudeenhancement of Tc to ~300 mK. Quantum oscillations show that superconductivityarises from spin-valley polarized Fermi surfaces, while in-plane magnetic fieldmeasurements reveal a Pauli limit violation that can be continuously tuned withdoping. I will then describe theoretical work suggesting plausible mechanismsfor the enhancement of pairing by WSe₂, and show how competitionbetween proximity-induced spin-orbit couplings and orbital effects can accountfor the doping dependence of the Pauli limit violation. These results pave theway for engineering robust, tunable and ultra-clean graphene-basedsuperconductors.

[1] Isospin magnetism and spin-polarizedsuperconductivity in Bernal bilayer graphene, H. Zhou, L. Holleis, Y. Saito, L. Cohen, W. Huynh, C. L. Patterson,F. Yang, T. Taniguchi, K. Watanabe, A. F. Young. Science 375(2021)

[2] Enhancedsuperconductivity in spin-orbit proximitized Bernal bilayer graphene, Y. Zhang, R.Polski, A. Thomson, ÉLH, C. Lewandowski, H. Zhou, K. Watanabe, T.Taniguchi, J. Alicea, and S. Nadj-Perge, arXiv:2205.05087.