Ising Superconductivity in Bernal Bilayer Graphene WSe₂ Heterostructures

Bernal Bilayer Graphene features a gate-tuned van Hove singularity, leading to a cascade of symmetry breaking states [1]. Surprisingly, superconductivity emerges above a critical in plane magnetic field, and is not Pauli limited, suggesting a spin triplet order parameter. Recently, it has been shown that superconductivity can be stabilized at zero magnetic field—and ten times higher temperature—by supporting the graphene bilayer on a monolayer of WSe2 [2]. WSe2 substrates are known to introduce Ising spin-orbit coupling (SOC), raising questions about possible changes to the magnetic phase diagram and superconducting order parameter that might account for the change in critical temperature. I will describe transport and capacitance measurements of WSe2 supported BBG with large spin orbit coupling. We report the observation of several distinct superconducting states; for all of these, the magnetic field dependence of the critical temperature is in good agreement with expectations for Ising superconductivity. Using penetration field capacitance and quantum oscillation measurements, we analyze the underlying phases of both superconductors and their Fermiology to construct a full phase diagram of BBG with monolayer WSe2. We will discuss these results in the context of general mechanisms for superconductivity in graphene multilayers without twist.

[1] H. Zhou, L. Holleis, Y. Saito, L. Cohen, W. Huynh, C. L. Patterson, F. Yang, T. Taniguchi, K. Watanabe, A. F. Young, Science 375, 774–778 (2022)

[2] Y. Zhang, R. Polski, A. Thomson, É. Lantagne-Hurtubise, C. Lewandowski, H. Zhou, K. Watanabe, T. Taniguchi, J. Alicea, S. Nadj-Perge, arXiv:2205.05087v1