Prediction of phonon-mediated superconductivity and topological surface states in NbRu3C

Based on the first-principles calculations, we obtain the superconducting transition temperature (Tc) of 21.17 K for NbRu3C. For the superconductivity of NbRu3C, the strong electron–phonon coupling mainly comes from the coupling between Ru 4d orbitals and low-energy phonon modes which include triply degenerate T1u and doubly degenerate E. Moreover, NbRu3C is found to have a topological insulating phase, confirmed by the calculated nontrivial surface states and spin textures. The presence of superconductivity and topological surface states in NbRu3C suggests that NbRu3C may be a candidate for the topological superconductor.