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

TL;DR

This study uses first-principles calculations to propose LaO(001) as a promising substrate for FeSe monolayer growth, potentially enhancing superconductivity through favorable magnetic fluctuations and electron doping.

Contribution

It introduces LaO(001) as a new substrate candidate for FeSe monolayer superconductivity, highlighting its magnetic and electronic properties that support superconductivity.

Findings

FeSe on LaO(001) exhibits near-degenerate magnetic states, indicating strong magnetic fluctuations.

Electron doping from LaO to FeSe is about 0.18 electrons per Fe, higher than in FeSe/SrTiO3.

LaO's superconductivity may induce a proximity effect on FeSe monolayer.

Abstract

The significantly enhanced superconducting transition temperature ($T_c$) of an FeSe monolayer on 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 FeSe monolayer to realize superconductivity. Our calculations show that for the optimal adsorption structure of 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 case of FeSe/SrTiO$_3$(001). Since LaO was also reported to be a superconductor with $T_c$ ~ 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 the interface-related superconductivity.