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

High temperature superconductivity in one unit cell (1 UC) FeSe on SrTiO3 heterostructure has become a research frontier in condensed matter physics and material science. The superconducting transition temperature (Tc) 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 Tc enhancement, electron pairing and topological phases in 1 UC FeSe on SrTiO3. The potential coexistence of high temperature superconductivity and topological electronic states promotes such two dimensional heterostructure as the candidate of next generation connate high temperature topological superconductor and (or) topological quantum computation platform.