Displacement-Field-Driven Transition between Superconducting and Ferromagnetic instabilities: A Case Study of Twisted Bilayer WSe2

Recent experiments have observed superconductivity and correlated magnetism in twisted bilayer $WSe_2$ along van-Hove fillings at different displacement field strengths $D$. Here, we theoretically propose a mechanism for a displacement-field-driven phase transition between superconducting and ferromagnetic phases induced by six van Hove singularities (VHS) in a 2D Ising superconductor. The key observation here is that the electronic interactions between different VHS evolve with the displacement field $D$ in different ways. By performing renormalization group analyses for these inter-VHS interactions at different $D$'s with experimentally extracted parameters, we find a chiral $p/d$-wave superconductivity ($p/d$-SC) when $D<D_c$ is small but finite. In contrast, at a larger displacement field $D>D_c$, a non-uniform ferromagnetic phase with an $f$-wave form factor ($f$-FM) dominates over the $p/d$-SC by satisfying the Stoner criteria. I will discuss possible detections for the proposed $p/d$-SC and $f$-FM phases, and how the proposed phase transition can generally occur in 2D spin-orbit-coupled hexagonal superconductors near van Hove fillings.