Interface suppressed nematicity and enhanced superconductivity of FeSe/NdFeO3 in the low doping regime

Abstract

The discovery of interface-enhanced superconductivity in single-layer FeSe/oxides has generated intensive research interests. Beyond the family of FeSe interfaced with various TiO${}_2$ terminated oxides, high pairing temperature up to 80~K has been recently observed in FeSe interfaced with FeO${}_x$-terminated LaFeO${}_3$. Here we successfully extend the FeSe/FeO${}_x$ superconducting interface to FeSe/NdFeO${}_3$, by constructing 1uc-FeSe/6uc-NdFeO${}_3$/Nb:SrTiO${}_3$ heterostructures. Intriguingly, well-annealed FeSe/NdFeO${}_3$ exhibits a low doping level of 0.038$\sim$0.046 ~e${}^{-}/$Fe which deviates universally magic doping level (0.10$\sim$0.12 e${}^{-}/\mathrm{Fe}$) and provides a new playground for studying the FeSe/oxide interface in the low electron-doped regime. Comparing it with thick FeSe films at the comparable electron doping level induced by surface potassium dosing, FeSe/NdFeO${}_3$ shows a larger superconducting gap and the absence of a nematic gap, indicating an enhancement of the superconductivity and suppression of nematicity by the FeSe/FeO${}_x$ interface. These results not only expand the FeSe/FeO${}_x$ superconducting family but also enrich the current understanding on the roles of the oxide interface.

8 pages, 4 figures