Electronic structure of new iron-based superconductors: From pnictides to chalcogenides and other similar systems

The electronic spectra of new iron-based high-temperature superconductors and a number of other chemically similar compounds have been discussed and compared with the focus on iron chalcogenide K_{1 ? x} Fe_{2 ? y} Se₂ and isostructural pnictide BaFe₂As₂ (122). It has been shown that the Fermi surfaces in K_{1 ? x} Fe_{2 ? y} Se₂ are significantly different from those in pnictides. The LDA + DMFT and LDA’ + DMFT calculations have demonstrated that the effect of electron correlations in K_{1 ? x} Fe_{2 ? y} Se₂ on the electronic structure is much stronger than that in the most studied 122 system. The electronic structure of several multiband superconductors similar in chemical composition to iron-based high-temperature superconductors, but having a relatively low T _c value (such as SrPt₂As₂, APt₃P (A = Sr, Ca, La), and (Sr, Ca)Pd₂As₂), and the non-superconducting compound BaFe₂Se₃ has also been discussed. It has been shown that the electronic structure of these systems is significantly different from previously studied iron pnictides and chalcogenides. The T _c value in these systems can be understood within the simple Bardeen-Cooper-Schrieffer model.