Topological superconducting states in monolayer FeSe/SrTiO3

The monolayer FeSe with a thickness of one unit cell grown on a single-crystal SrTiO3 substrate (FeSe/STO) exhibits striking high-temperature superconductivity with transition temperature T-c over 65 K reported by recent experimental measurements. In this work, through analyzing the distinctive electronic structure, and providing systematic classification of the pairing symmetry, we find that both s- and p-wave pairing with odd parity give rise to topological superconducting states in monolayer FeSe, and the exotic properties of s-wave topological superconducting states have close relations with the unique nonsymmorphic lattice structure which induces the orbital-momentum locking. Our results indicate that the monolayer FeSe could be in the topological nontrivial s-wave superconducting states if the relevant effective pairing interactions are dominant in comparison with other candidates.