Superconductivity in topological nodal line semimetals

We theoretically investigate the superconductivity induced by ferromagnetic fluctuations in doped nodal line semimetals (NLSMs). We find that only spin triplet pairing channels are favored and also derive the critical temperatures for the leading instability. We show that the superconudcting state in an orbital singlet and spin triplet channel displays nodal rings on the torus-like Fermi surface (FS). From the prior results on tenfold way classifications for gapless systems with inversion symmetry, the Bogoliubov-de Gennes (BdG) Hamiltonian in our model belongs to the CI class and the BdG nodal rings are protected by an integer topological charge ±2. In the presence of a ferromagnetic order, the superconducting nodal ring is split into two rings with charge ±1.