The relationship between magnetism and superconductivity has been one of the most discussed topics in iron-based superconductors. Using the first-principles calculations, we have studied the electronic structure of 1144-type iron-based superconductor EuRbFe4As4. We find the crystal field splitting of EuRbFe4As4 is unique, such that the dz2 orbitals are closer to the Fermi level ϵF than the dxy orbitals. The RKKY interaction strength is estimated to be approximately 0.12 meV in prestine EuRbFe4As4. Upon Ni-doping on the Fe site, the RKKY interaction strength is barely changed upon Ni doping due to the highly anisotropic FSs and multiband effect, despite of the drastically reduced dzx(y) DOS at ϵF. Finally, in both pristine and doped compounds, the RKKY interaction is primarily mediated through bands due to Fe-dz2 orbitals.Our calculations suggest the RKKY interaction mediated by dz2 orbital is probably responsible for the magnetism in EuRbFe4As4 and doesn't change upon Ni-doping.
@article{arxiv.1902.06867,
title = {Electronic structure of Ni-doped EuRbFe$_4$As$_4$: Unique crystal field splitting and multiband RKKY interactions},
author = {Chenchao Xu and Qijin Chen and Chao Cao},
journal= {arXiv preprint arXiv:1902.06867},
year = {2019}
}