Interplay of Superconductivity, Magnetism, and Isospin Fluctuations in Rhombohedral Graphene

The flat-band regime of rhombohedral multilayer graphene (RMG) offers a uniquely tunable platform for correlated electron physics, where the high density of states stabilizes a wide range of symmetry-broken phases. Recent experiments have revealed a diverse set of superconducting states in RMG, coexisting with spin- and valley-polarized phases that dominate its phase diagram. Unlike in most materials, superconductivity and magnetism are not mutually exclusive here. In this talk, I will present transport and thermodynamic measurements probing their interplay in RMG devices on different substrates. I will map the magnetic phase diagram near superconductivity, uncovering spin-canted phases, and discuss the implications for possible pairing mechanisms. Remarkably, even above the critical temperatures of magnetic and superconducting order, RMG exhibits large excess entropy and pronounced Pomeranchuk effects driven by isospin fluctuations—behavior reminiscent of local moments despite the itinerant nature of the electron wave functions raising the question how local moments form from bands with strong Berry curvature. I will also highlight recent advances in fabricating high-yield, large-area RMG van-der-Waals structures, which open new opportunities for mesoscopic devices.