  The enhanced superconductivity in monolayer FeSe on titanates opens a
fascinating pathway towards the rational design of high-temperature
superconductors. Utilizing the state-of-the-art oxide plus chalcogenide
molecular beam epitaxy systems in situ connected to a synchrotron
angle-resolved photoemission spectroscope, epitaxial LaTiO3 layers with varied
atomic thicknesses are inserted between monolayer FeSe and SrTiO3, for
systematic modulation of interfacial chemical potential.With the dramatic
increase of electron accumulation at the LaTiO3-SrTiO3 surface, providing a
substantial surge of work function mismatch across the FeSe-oxide interface,
the charge transfer and the superconducting gap in the monolayer FeSe are found
to remain markedly robust. This unexpected finding indicates the existence of
an intrinsically anchored magic doping within the monolayer FeSe systems.
