Inferior Interfacial Superconductivity in 1 UC FeSe/SrVO₃/SrTiO₃ with Screened Interfacial Electron–Phonon Coupling

Single-unit cell (1 UC) FeSe interfaced with TiO_<i>x</i> or FeO_<i>x</i> exhibits significantly enhanced superconductivity compared to that of bulk FeSe, with interfacial electron-phonon coupling (EPC) playing a crucial role. However, the reduced dimensionality in 1 UC FeSe, which may drive superconducting fluctuations, complicates our understanding of the enhancement mechanisms. We construct a new superconducting interface, 1 UC FeSe/SrVO₃/SrTiO₃. Here, the itinerant electrons of highly metallic SrVO₃ films can screen all high-energy Fuchs-Kliewer phonons, including those of SrTiO₃, making it the first FeSe/oxide system with screened interfacial EPC while maintaining the 1 UC FeSe thickness. Despite comparable doping levels, the heavily electron-doped 1 UC FeSe/SrVO₃ exhibits a pairing temperature (<i>T</i>_g ∼ 48 K) lower than those of FeSe/SrTiO₃ and FeSe/LaFeO₃. Our findings disentangle the contributions of interfacial EPC from dimensionality in terms of enhancing <i>T</i>_g in FeSe/oxide interfaces, underscoring the critical importance of interfacial EPC. This FeSe/VO_<i>x</i> interface also provides a platform for studying interfacial superconductivity.