Probing magnetism and Chiral superconductivity in rhombohedral graphene

We report on three complementary investigations of strongly correlated phases in rhombohedral multilayer graphene, enabled by high-resolution magnetic imaging with a scanning SQUID-on-tip. In rhombohedral tetralayer graphene, we directly visualize isospin magnetic textures and identify sharp, spontaneous phase transitions that break time-reversal symmetry. Analysis of spin and orbital alignment in the quarter-metal phase provides an experimental bound on the spin–orbit coupling energy, while the weak anisotropy in the half-metal phase yields a lower bound on the intervalley Hund’s exchange interaction, approaching its theoretical maximum [1]. In a second study, we investigate a WS₂-proximitized pentalayer graphene device and uncover a high-Chern-number (C = –5) quantum anomalous Hall (QAH) insulator. The QAH state emerges from a layer-antiferromagnetic background through a first-order transition and exhibits distinct spatial signatures of orbital magnetism, including patterned magnetic domains. Adjacent to this phase, we identify a metallic regime with fluctuating, valley-dependent magnetism [2]. Finally, we present preliminary indications of chiral superconductivity in pentalayer graphene, where a superconducting dome arises within a symmetry-broken quarter-metal phase. Magnetic imaging reveals rich spatial variations in magnetization surrounding the superconducting region, indicating a complex landscape of coexisting orders. These results highlight the utility of nanoscale magnetic imaging in probing the microscopic origins of symmetry breaking, topology, and unconventional superconductivity in rhombohedral multilayer graphene.