SPICE Workshop on Unconventional Superconductors and Magnets May 12th - 14th, 2026
Long Ju
Rhombohedral stacking is a crystalline form of natural graphite. At the few-layer limit, rhombohedral graphene exhibits electrically tunable band structures and Berry curvature. Various spin and valley symmetry-broken states have been observed in such systems, fostering highly unconventional superconductivities. I will discuss the most exotic one in which the electrical resistance shows magnetic hysteresis at both above and below the transition temperature—a phenomenon that has not been observed in any other superconductors. This observation indicates a spontaneous time-reversal-symmetry-breaking at the orbital level, thus defining the chirality of the Cooper pairs. I will also discuss other superconducting states observed in multi-layer rhombohedral graphene, most of which exhibit Pauli-Limit-Violation of tens of times and spin-polarized superconductivity. Rhombohedral graphene therefore provides an ideal platform to study unconventional superconductivity, featuring a highly crystalline order, low defect level, electrical tunability and co-existence with other topological phases of matters, such as integer and fractional quantum anomalous Hall effects.