Oral: Diverse Impacts of Spin-Orbit Coupling on Superconductivity in Rhombohedral Graphene

Spin-orbit coupling (SOC) has played an important role in many topological and correlated electron materials. In graphene-based systems, SOC induced by transition metal dichalcogenide (TMD) at proximity was shown to drive topological states and strengthen superconductivity. Rhombohedral multilayer graphene with layer N≥3 is a robust platform of electron topology, exhibiting both integer & fractional quantum anomalous Hall effect. However, superconductivity and the role of SOC in such systems remain largely unexplored. Here we report transport study of TMD-proximitized rhombohedral trilayer graphene (RTG). We observed a new hole-doped superconducting state SC4 with Tc = 230 mK. On the electron-doped side, we identified a new symmetry-breaking three-quarter-metal (TQM) phase. Near the TQM, the originally weak SC3 is fully developed into a superconducting state with Tc = 110 mK. The behavior of SC3 and SC4 are aligned with the existing understanding that SOC enhances graphene superconductivity. Surprisingly, the original superconducting state SC1 in bare RTG is strongly suppressed in the presence of TMD and is missing down to 40 mK - opposite to all other graphene superconductivities. Our observations provide experimental evidence that challenges the understanding of the impacts of SOC on graphene superconductivity.