Topological p plus ip superconductivity in doped graphene-like single-sheet materials BC3

We theoretically study exotic superconducting phases in graphene-like single-sheet material BC3 doped to its type-II van Hove singularity whose saddle-point momenta are not time-reversal invariant. From combined renormalization group analysis and random-phase approximation calculations, we show that the dominant superconducting instability induced by weak repulsive interactions is in the time-reversal-invariant p + ip pairing channel because of the interplay among dominant ferromagnetic fluctuations, subleading spin fluctuations at finite momentum, and spin-orbit coupling. Such time-reversal-invariant p + ip superconductivity has nontrivial Z(2) topological invariant. Our results show that doped BC3 provides a promising route to realizing a genuine two-dimensional helical p + ip superconductor.