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$_{2-y}$Se$_2$ and isostructural pnictide BaFe$_2$As$_2$ (122). It has been shown that the Fermi surfaces in K$_{1-x}$Fe$_{2-y}$Se$_2$ 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$_{2-y}$Se$_2$ 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 SrPt$_{2}$As$_{2}$, APt$_{3}$P (A = Sr, Ca, La), and (Sr, Ca)Pd$_2$As$_2$), and the non-superconducting compound BaFe$_2$Se$_3$ 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.