  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.
