Importance of the Fermi surface and magnetic interactions for the superconducting dome in electron-doped FeSe intercalates

摘要

The van-der-Waals gap of iron chalcogenide superconductors can be intercalated with a variety of inorganic and organic compounds that modify the electron doping level of the iron layers. In Li_x(C_3N_2H_(10))_(0.37)FeSe,a dome in the superconducting transition temperature T_c has been reported to occur in the doping range of ⅹ = 0.06 to ⅹ = 0.68. We use a combination of density functional theory and spin fluctuation theory to capture the evolution of superconducting transition temperatures theoretically. We clearly demonstrate how the changing electronic structure supports an increasing superconducting T_c. The suppression of T_c at high doping levels can, however, only be understood by analyzing the magnetic tendencies, which evolve from stripe-type at low doping to bicollinear at high doping.