Interface-Suppressed Nematicity and Enhanced Superconducting Pairing Strength of FeSe/NdFeO in the Low-Doping Regime.

The discovery of interfacial superconductivity in monolayer FeSe/oxides has spurred intensive research interest. Here we not only extend the FeSe/FeO superconducting interface to FeSe/NdFeO but also establish robust interface-enhanced superconductivity at a very low doping level. Specifically, well-annealed FeSe/NdFeO exhibits a low doping level of 0.038-0.046 e/Fe with a larger superconducting pairing gap without a nematic gap, indicating an enhancement of the enhanced superconducting pairing strength and suppression of nematicity by the FeSe/FeO interface compared with those of thick FeSe films. These results improve our understanding of the roles of the oxide interface in the low-electron-doped regime.