The interface-enhanced superconductivity of FeSe/SrTiO3 has been one of the most attractive topics in the field of condensed matter physics.Fabricating heterostructures based on ultrathin FeSe films provides a promising method to tune their superconductivity and to construct novel quantum states.Here,we prepared high-quality CoSe/FeSe vertical heterostructure films on SrTiO3(001)substrate by molecular beam epitaxy.Scanning tunneling microscopy(STM)and scanning tunneling spectroscopy(STS)were employed to investigate their electronic properties and the spatial distribution of electronic states.Due to the significant interfacial charge transfer from CoSe to FeSe,FeSe was in an over-doped state,which broken the non-adiabatic approximation in FeSe/STO and suppressed its superconductivity.The space-resolved STS measurements revealed the direction-dependent edge states and corner states tuned by the interfacial charge transfer at the CoSe/FeSe interface.This work provides a reference for the tuning of superconductivity and the construction of quantum structures based on single-layer FeSe/SrTiO3.
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