Bi on Ge (111)

Unconventional superconductivity stems from strong anisotropic electron correlation in the momentum space. For systems with nonvanishing Berry curvature, the electron-electron scatterings in the reciprocal space will acquire additional geometric (Berry) phases, thus enhancing the degrees of freedom for accommodating the anisotropy of electron correlation. Here, we explore the exotic superconducting phases in doped monolayer Pb₃Bi grown on Ge (111). First, based on first-principles calculations, we reveal a large Rashba-type spin-orbit splitting of the band structure and a type-II van Hove singularity of the density of states below the Fermi level. Next, a phenomenological low-energy model is developed to capture the essential physics at the van Hove filling. Using renormalization group method, we find that a superconducting instability with p-wave pairing symmetry can be induced by Berry phase effect within repulsive electron-electron interaction, and dominates over other competing orders in the weak interaction regime. Furthermore, condensation energy calculations show that the superconducting state prefers fully-gapped chiral p_x+ip_y pairing symmetry. These results demonstrate that monolayer Pb₃Bi is a promising candidate for realizing intrinsic topological superconductivity.