Role of the charge-transfer induced electric field in potassium-dosed FeSe layers

Potassium-dosed FeSe layers are investigated using the density functional theory combined with the dynamical mean-field theory. We show that K dosing induces the charge transfer from K atoms to the topmost FeSe layer, and subsequently, ionized K atoms generate a strong local electric field. Role of this charge-transfer induced electric field is discussed with emphasis on its impacts on the electronic structure and electron correlation among Fe 3d orbitals. By controlling the concentration of K atoms, we systematically investigate the evolution of the electronic structure of both FeSe mono and bilayers. Notably, K dosing reduces bandwidths of the Fe 3d bands near the Fermi level and significantly enhances electron correlation. We also discuss the structural changes of FeSe layers due to K dosing. Our results illustrate that charge transfer from external agents in electron-doped FeSe systems can have nontrivial effects other than electron doping and account for their enhanced electron correlation.