Nematic, chiral and topological superconductivity in transition metal dichalcogenides

We introduce and study a realistic model for superconductivity in twisted bilayer WSe$_{2}$, where electron pairing arises from spin-valley fluctuations in the weak-coupling regime. Our model comprises both the full continuum model moir\'{e} bandstructure and a short-ranged repulsive interaction that accounts for the Coulomb interaction projected onto the localized Wannier orbitals. By calculating the spin-valley susceptibility, we identify a Fermi surface nesting feature near half-filling of the top-most moir\'{e} band, which induces significantly enhanced spin-valley fluctuations. We then analyze the dominant Kohn-Luttinger pairing instabilities due to these spin-valley fluctuations and show that the leading instability can induce nematic, chiral and topological superconductivity. As our findings are asymptotically exact for small interaction strengths, they provide a viable starting point for future studies of superconductivity in twisted transition metal dichalcogenide bilayers.