Electronic Properties and Fermi Surface for New Layered High-Temperature Superconductors CaAFe4As4 (A = K, Rb, and Cs): FLAPW-GGA Calculations

Recently, new FeAs-based high-temperature superconductors CaAFe(4)As(4) (A = K, Rb, and Cs) with a layered tetragonal crystal structure were synthesized (T (C) 30 K). In this letter, we report for the first time the band structures, Fermi surface topology, total and partial densities of electronic states, and interatomic interactions for CaAFe(4)As(4) as estimated by means of the first-principle FLAPW-GGA calculations. The obtained data for CaAFe(4)As(4) phases are analyzed in comparison with each other and with other related FeAs systems. The interatomic bonding picture can be represented as a highly anisotropic mixture of metallic, covalent, and ionic contributions, which are realized inside Fe4As4-layered blocks and between these blocks and Ca, A atomic sheets. The Fermi surfaces of these systems have a multisheet character and are compiled of a large number of cylinders at the edges and in the central part of the Brillouin zone. It is established that the high-temperature superconductivity in CaAFe(4)As(4) compounds as in other related systems correlates well with such structure parameters as bond angles and anion height.