The electronic structure, magnetism and Fermi surface of a hole self-doped potential iron-based superconductor KCa2Fe4As4O2 (12442) were studied by a first-principes DFT/GGA approach. The projection onto Wannier functions basis is proposed to calculate directly the self-doping value. In particular for KCa2Fe4As4O2 it is 0.75 hole on Fe-3d states. Surprisingly, for the KCa2Fe4As4O2 it was found that except the Fe-3d bands the O-2p bands also cross the Fermi level, which is quite anomalous behavior for O-2p states. In general, the O-2p states are usually fully occupied in transition metal oxides. Here it is not the case due to the fact that CaO layer gives some of the electrons to the FeAs layer, thus leaving O-2p states partially occupied. The O-2p states form additional Fermi surface sheet with propeller-like shape around Γ-point and modify the Fe-3d Fermi surface sheets due to the hybridization. To prove the presence of anomalous metallic O-2p band in KCa2Fe4As4O2 the comparative study with the same family systems KCa2Fe4As4F2 and RbGd2Fe4As4O2 (where it is not the case) was performed. The magnetic ground state is found to be antiferromagnetic with checkerboard ordering. Therefore, we expect that the KCa2Fe4As4O2 might be a potential superconductor with unusual properties.
@article{arxiv.2205.07007,
title = {Anomalous metallic oxygen band in the potential superconductor KCa$_2$Fe$_4$As$_4$O$_2$},
author = {Nikita S. Pavlov and Kirill S. Pervakov and Igor A. Nekrasov},
journal= {arXiv preprint arXiv:2205.07007},
year = {2023}
}