Heterostructural one-unit-cell FeSe/SrTiO3: from high-temperature superconductivity to topological states

High-temperature superconductivity in one-unit-cell (1-UC) FeSe/SrTiO3 heterostructure has become a research frontier in condensed-matter physics and material science. The superconducting transition temperature (T-c) of ultrathin FeSe film is significantly enhanced compared to its bulk counterpart and possibly approaches the liquid-nitrogen region according to in situ spectroscopic measurements. Particularly, the Fermi-surface topology of 1-UC FeSe consists of no hole pockets at Brillouin-zone center, which poses a great challenge to the well-accepted s(+/-)-wave pairing nesting the sign-different electron-hole Fermi pockets in iron-based superconductors. In this review, we present the explorations of T-c-enhancing factors, superconducting pairing mechanism and potential topological phases in 1-UC FeSe/SrTiO3. The possible coexistence of high-temperature superconductivity and topological electronic states promotes such 2D heterostructure as the candidate of next-generation connate high-temperature topological superconductor and/or topological-quantum-computation platform.