Isospin magnetism and spin-polarized superconductivity in Bernal bilayer graphene

We report the observation of spin-polarized superconductivity in Bernal bilayer graphene when doped to a saddle-point van Hove singularity generated by large applied perpendicular electric field.   We observe a cascade of electrostatic gate-tuned transitions between electronic phases distinguished by their polarization within the isospin space defined by the combination of the spin and momentum-space valley degrees of freedom. While all of these phases are metallic at zero magnetic field, we observe a transition to a superconducting state at finite B|| ≈ 150mT applied parallel to the two dimensional sheet. Superconductivity occurs near a symmetry breaking transition, and exists exclusively above the B||-limit expected of a paramagnetic superconductor with the observed Tc ≈ 30mK, implying a spin-triplet order parameter.Â