Interplay between Rashba Spin-Orbit Coupling, Magnetic Field, and Topological Superconductivity in Monolayer NbSe_2

The persistence of superconductivity above the Pauli limit in monolayer 1H-NbSe_2 is indicative of strong Ising spin-orbit coupling (SOC). It has been suggested that the interplay between Ising SOC and strong in-plane magnetic fields can lead to a topological nodal superconducting phase protected by a time reversal-like symmetry. An important ingredient not fully considered, however, is Rashba SOC. Not only is it expected to be significant due to substrate effects, but it is also tunable by electrostatic gating. In this talk, we present a microscopic model for superconductivity of NbSe_2 driven by repulsive electronic interactions as a function of magnetic field and Rashba SOC. For large enough magnetic fields, a small Rashba SOC lifts the nodes unless the magnetic field is aligned along certain directions, in which case a residual mirror symmetry protects some of the nodes and corresponding flat band edge modes. In the opposite limit of small magnetic fields, a topological chiral phase is found to be stabilized by large Rashba SOC.