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.