Inducing chiral bound states in multilayer graphene via Berry curvature: Analytical and numerical approach

Rhombohedral graphene can host spin-valley polarized quarter metal phases at low temperatures. We investigate the formation of two-electron bound states in this phase using both analytical and numerical methods. As the system is already spin-polarized, Fermi statistics require the orbital wavefunction of the bound state to have odd symmetries, favoring a p-wave. Using a simple yet realistic toy model for the bound state, we argue that Berry curvature associated with the graphene bandstructure further lowers the energy of the chiral linear superposition of the p-wave states, favoring a chiral p+ip bound state as the ground state. Signatures of chiral superconductivity have been observed in some recent experiments. Our results indicate that Berry curvature enhances the formation of two-electron bound state, which contributes towards a clear picture of the microscopic mechanism of superconductivity observed in rhombohedral stacking of graphene layers. Moreover, we study the energetics of the bound state as a function of the number of graphene layers, and discuss why it is feasible to experimentally observe chiral superconductivity by stacking a few layers.