Correlated metals and unconventional superconductivity in rhombohedral trilayer graphene: A renormalization group analysis

Motivated by recent experimental observations of correlated metallic phases and superconductivity in rhombo-hedral trilayer graphene (RTG), we perform an unbiased study of electronic ordering instabilities in hole-doped RTG. Specifically, we focus on electronic states energetically proximate to Van Hove singularities (VHSs), where a large density of states promotes different interaction-induced symmetry-breaking electronic orders. To resolve the Fermi surface near VHSs, we construct a fermionic hot-spot model and demonstrate that a perpendicular electric field can tune different nesting structures of the Fermi surface. Subsequently, we apply a renormalization group analysis to describe the low-energy phase diagrams of our model under both short-range repulsive interactions as well as realistic (long-range) Coulomb interactions. Our analysis shows instabilities towards either intervalley coherent metallic phases or superconducting phases. The dominant pairing channel depends crucially on the nature of Fermi surface nesting-repulsive Coulomb interaction favors spin-singlet d-wave pairing for relatively small displacement field and spin-singlet i-wave pairing for larger displacement field. We argue that the phase diagram of RTG can be well-understood by modeling the realistic Coulomb interaction as the sum of repulsive density-density interaction and ferromagnetic spin-triplet intervalley coherence (IVC) Hund's coupling, while phonon-mediated electronic interactions have a negligible effect on this system, in sharp contrast to twisted graphene multilayers.

Automated summary

Motivated by recent experimental observations, this study investigates the electronic ordering instabilities in hole-doped rhombohedral trilayer graphene (RTG). The Fermi surface near Van Hove singularities (VHSs) is resolved using a fermionic hot-spot model, showing possibilities of metallic or superconducting phases. The dominant pairing channel depends on the Fermi surface nesting and Coulomb interaction.