Topological superconductivity in Sn/Si(111) driven by nonlocal Coulomb interactions

Superconductivity was recently observed in boron-doped (root 3 x root 3)Sn/Si(111). The material can be de-scribed by an extended Hubbard model on a triangular lattice. Here, we use the random-phase approximation to investigate the charge and spin fluctuations as well as the superconducting properties of the system with respect to filling and the relative strength of the extended versus the on-site Hubbard interactions. Our calculations reveal that near half-filling and weak extended Hubbard interactions, the superconducting ground state exhibits chiral d-wave pairing. Far from half filling and for stronger nearest-neighbor Coulomb interactions, the system shows chiral p-wave (hole-doping) and f-wave (electron-doping) pairings. The dependence of the pairing symmetry on the extended Hubbard interactions suggests that charge fluctuations play an important role in the formation of Cooper pairs. Finally, the temperature dependence of the Knight shift is calculated for all observed superconducting textures and put forward as an experimental method to examine the symmetry of the superconducting gap function.

Automated summary

Superconductivity in boron-doped (root 3 x root 3)Sn/Si(111) was studied using the random-phase approximation. The results showed that under certain conditions, chiral d-wave pairing was observed near half-filling and weak extended Hubbard interactions, while chiral p-wave and f-wave pairings were present at different filling levels and stronger nearest-neighbor Coulomb interactions. These findings suggest that charge fluctuations play a significant role in the formation of Cooper pairs, and the temperature dependence of the Knight shift can be used to examine the symmetry of the superconducting gap function.