High temperature superconductivity at FeSe/LaFeO interface.

Enormous enhancement of superconducting pairing temperature (T) to 65 K in FeSe/SrTiO has made it a spotlight. Despite the effort of interfacial engineering, FeSe interfaced with TiO remains the unique case in hosting high T, hindering a decisive understanding on the general mechanism and ways to further improving T. Here we constructed a new high-T interface, single-layer FeSe interfaced with FeO-terminated LaFeO. Large superconducting gap and diamagnetic response evidence that the superconducting pairing can emerge near 80 K, highest amongst all-known interfacial superconductors. Combining various techniques, we reveal interfacial charge transfer and strong interfacial electron-phonon coupling (EPC) in FeSe/LaFeO, showing that the cooperative pairing mechanism works beyond FeSe-TiO. Intriguingly, the stronger interfacial EPC than that in FeSe/SrTiO is likely induced by the stronger interfacial bonding in FeSe/LaFeO, and can explain the higher T according to recent theoretical calculations, pointing out a workable route in designing new interfaces to achieve higher T.