Doping-induced antiferromagnetic bicollinear insulating state and superconducting temperature of monolayer FeSe systems

First-principles calculations of ionic-liquid-gated (Li,Fe)OHFeSe suggest a metal-insulator transition at a nominal Li/Fe ratio of 75/25 in the (Li,Fe)OH layer. While doping increases Fermi energy, the formation of an antiferromagnetic bicollinear phase is the key for the transition. It is expected that this insulating phase also exists in other FeSe systems upon heavy electron doping, and its presence can hinder the increase of superconducting temperature. These results offer clues on how to optimize superconductivity amid its interplay with magnetic properties in FeSe systems.