Spin-polarized superconductivity in semimetallic rhombohedral graphene: Part II

Rhombohedral graphene has emerged as a highly tunable platform for correlated and topological phenomena, including unconventional superconductivity and integer/fractional Chern insulators. In both moiré and non-moiré devices, most studies have focused on high displacement fields in samples with six or fewer layers, where charge neutrality is gapped. With increasing layer number, however, rhombohedral graphene remains semimetallic over a broad range of carrier density and displacement field. In Part I of this talk, we showed in an unaligned octalayer sample that this semimetallic regime realizes a surface-bifurcated charge distribution and can host superconductivity. Building on these results, here we discuss a heptalayer device with a moiré superlattice from alignment to hexagonal boron nitride. The device exhibits two distinct pockets of superconductivity within the dual-surface semimetal, connected by a single sharp resistive feature. At larger displacement fields, outside the semimetallic regime, this feature also nucleates an integer quantum anomalous Hall (IQAH) state near ν = 1. Applying an in-plane magnetic field triggers superconductivity along the entire resistive feature, extending close to the IQAH state and traversing both the band-isolated and semimetallic regions. These findings highlight the important roles of the dual-surface charge distribution, symmetry breaking, and intrinsic spin-orbit coupling in rhombohedral graphene.