Proximity-driven ferromagnetism and superconductivity in the triangular Rashba-Hubbard model

Bilayer moir\'e structures are a highly tunable laboratory to investigate the physics of strongly correlated electron systems. Moir\'e transition metal dichalcogenides (TMDs) at low energies, in particular, are believed to be described by a single narrow band Hubbard model on a triangular lattice. Motivated by recent experimental evidence for superconductivity in twisted bilayer materials, we investigate the possible superconducting pairings for TMDs deposited on a substrate by studying a two-dimensional single-band Rashba-Hubbard model. Using a random-phase approximation in the presence of nearest- and next-nearest-neighbor hopping, we analyze the structure of spin fluctuations and the symmetry of the superconducting gap function. We show that Rashba spin-orbit coupling favors ferromagnetic fluctuations which strengthen triplet superconductivity. If parity is violated due to the absence of spatial inversion symmetry, singlet ($d$-wave) and triplet ($p$-wave) channels of superconductivity will be mixed. Moreover, we show that time-reversal symmetry can be spontaneously broken, leading to a chiral superconducting state. Finally, we consider quasiparticle interference as a possible experimental technique to observe the superconducting gap symmetry.