Approximate symmetries, insulators, and superconductivity in the continuum-model description of twisted WSe 2

Motivated by the recent discovery of superconductivity in twisted bilayer WSe_{2}, we analyze the correlated physics in this system in the framework of a continuum model for the moiré superlattice. Using the symmetries in a fine-tuned limit of the system, we identify the strong-coupling ground states and their fate when the perturbations caused by finite bandwidth, displacement field, and the phase of the intralayer potential are taken into account. We classify the superconducting instabilities and, employing a spin-fermion-like model, study the superconducting instabilities in proximity to these insulating particle-hole orders. This reveals that only a neighboring intervalley coherent phase (with zero or nonzero wave vector) is naturally consistent with the observed superconducting state, which we show to be crucially affected by the nontrivial band topology. Depending on details, the superconductor will be nodal or a chiral gapped state while further including electron-phonon coupling leads to a fully gapped, time-reversal symmetric pairing state.