LaO as a candidate substrate for realizing superconductivity in an FeSe epitaxial film

The significantly enhanced superconducting transition temperature (${T}_{c}$) of an FeSe monolayer on ${\mathrm{SrTiO}}_{3}$(001) substrate has attracted extensive attention in recent years. Here, based on first-principles electronic structure calculations, we propose another candidate substrate, LaO(001), for the epitaxial growth of an FeSe monolayer to realize superconductivity. Our calculations show that for the optimal adsorption structure of the FeSe monolayer on LaO(001), the stripe antiferromagnetic state and the dimer antiferromagnetic state are almost energetically degenerate, indicating the existence of strong magnetic fluctuation that is beneficial to the appearance of superconductivity. According to the Bader charge analysis, the calculated electron doping from the LaO substrate to the FeSe monolayer is about 0.18 electrons per Fe atom, even larger than that in the case of FeSe/${\mathrm{SrTiO}}_{3}$(001). Since LaO was also reported to be a superconductor with ${T}_{c}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}5$ K, it may have a superconducting proximity effect on the epitaxial FeSe film and vice versa. These results suggest that LaO would be an interesting substrate to study interface-related superconductivity.