First-principles calculations of the electronic and possible topological properties of confirmed two-dimensional high T c superconductors Nb2CoS4, Nb2CuS4, and PtN2.

Recently, next generation two-dimensional high-T c superconductors have attracted intense interest. Motivated by this development, we had great interests to explore whether these high-T c superconducting monolayers has topological properties. Here, a systematic investigation of three high-temperature, two-dimensional superconductors Nb2CoS4, Nb2CuS4, and PtN2 was conducted to examine their electronic band structures. Their band structures without SOC displayed Dirac-like crossings near the Fermi level. Upon including SOC, we found virtual evidence for locally gapped Dirac-like crossings in hexagonal PtN2 and SOC-resolved nodal-ring features in the two niobium compounds. These phenomena indicated possible topologically nontrivial phases, suggesting that these high-T c superconductors are possible candidates for the ongoing search for topological superconductivity.