Microscopic Theory of Superconductivity in NbSe_2 Monolayer in Presence of a Magnetic Field

Monolayers of NbSe_2, a 2D transition metal dichalcogenide, have recently been found to be superconducting below a critical temperature of 3K. This superconducting state survives even in the presence of in-plane magnetic fields of up to 35 T, far above the Pauli limit, indicating strong out-of-plane spin-orbit coupling (SOC). This remarkable observation led to interesting theoretical proposals of Ising superconductivity and topological superconductivity in this and also in other similar 2D dichalcogenides. Here, we introduce a microscopic low-energy model for NbSe_2 monolayer that includes the Ising SOC, the Rashba SOC, an external in-plane magnetic field, and all possible low-energy electronic interactions. By performing a parquet renormalization group calculation, we investigate the superconducting instabilities of the system that arise due to purely repulsive interactions. We discuss the possible emergence of topological superconductivity and finite-momentum pairing, and compare our results with experiments.