The Energy Band Structure of A(x)Fe(2)Se(2) (A = K, Rb) Superconductors

We study the band structure of antiferromagnetic A(x)Fe(2)Se(2) (A = K, Rb) superconductors by using first-principles electronic structure calculations which is density functional theory. In the vicinity of iron-vacancy, we identify the valence electrons of A(x)Fe(2)Se(2) will be filled up to the Fermi level and no semiconducting gap is observed. Hence, the A(x)Fe(2)Se(2) is a metallic instead of semiconducting which leads to superconductivity in the orbital-selective Mott phase. Similarly, there is non-vanishing density of states at the Fermi level.