Iron Selenide Intercalated by Uncharged Molecules: Superconductivity in FeSe(C₂H₇NO)_0.3

Abstract

The charge‐neutral intercalated iron selenide compound FeSe(C2H7NO)0.3 is formed from FeSe(C2H8N2)0.3 through amine exchange under solvothermal conditions. Although the exchanged molecules are of similar size, the distance of the FeSe‐layers increases from 10.68 Å to 13.58 Å. The combination of Xray diffraction and DFT calculations suggests a chemically reasonable, albeit somewhat simplified, model for the orientation of the molecules between the FeSe layers, which interact via weak hydrogen bonds. The neutral guest species is unable to transfer charge to the FeSe layers, which remain electronically undoped. While the starting compound is non‐superconducting, the resulting product exhibits a transition to superconductivity at Tc = 14 K. The topology of the calculated Fermi surface undergoes only minimal alteration with increased layer spacing, a change that is considerably less pronounced than that observed with electron doping. Our findings indicate that undoped FeSe layers become superconducting when the interlayer distance is sufficiently large, while the highest critical temperatures necessitate additional electron doping.