The role of electron correlation in engineering high-temperature superconductivity in FeSe/SrTiO₃heterostructure

Controlling the superconducting transition temperature (T_C) through engineering atomic-scale geometry and understanding its relationship with the strong electron correlation can be a major step forward in the search for high-T_C superconductors. Here, we show such possibilities with FeSe monolayer grown on a SrTiO3(001) substrate by exploiting the interplay between electron and lattice through the first principles density functional theory (DFT) + dynamical mean-field theory (DMFT) method. By investigating the Fe-Ch-Fe (Ch=Se, Te, etc.) tetrahedral angle in single-layer FeX on various substrate terminations, our research unveils a significant correlation between T_C and atomic-scale geometry, which controls the strength of electron correlations. Our calculations reveal an optimal Fe-Ch-Fe angle of the FeSe tetrahedron where the measured Tc and the electron correlations peak for the FeSe-TiO₂ interface.