Electronic structure and magnetism of the 35 K superconductor CsEuFe4As4

The results of ab-initio calculations of the electronic structure and magnetism of the new 35 K superconductor CsEuFe4As4 are reported. The electronic band structure and the density of states are presented and discussed in detail. The origin of the chemical bonding between the constituent atoms is discussed in detail. The evidence is provided for the existence of a mixture of ionic, covalent, and metallic bonding. It is demonstrated that the magnetic moment is mainly due to the strongly localized Eu f states. No spin polarization at the Fe sites is found. It is demonstrated that the electrical conductivity in CsEuFe4As4 originates from the Fe contribution to the density of states. The electrical and chemical properties of the studied compound are closely linked with the presence of the Fe d states in the Fermi energy region. The Fermi surfaces show the presence of the hole-like and electron-like pockets, respectively, at the center and corners of the Brillouin zone. The results of the calculations of the 57Fe and 151Eu hyperfine-interaction parameters are also presented. •A mixture of ionic, covalent, and metallic bonding is present in CsEuFe4As4.•The magnetic moment is due to the strongly localized Eu f states.•The Fe atoms do not carry any magnetic moment.•The transport properties of CsEuFe4As4 are the result of the presence of the Fe d states in the Fermi energy region.•The Fermi surfaces are in the form of the hole-like and electron-like pockets.