Electronic structure of InCo$_2$As$_2$ and KInCo$_4$As$_4$: LDA + DMFT

A comparative analysis of the electronic structure obtained in the DFT/LDA and LDA + DMFT approaches of the possible isostructural analogues of iron superconductors InCo$_2$As$_2$ and KInCo$_4$As$_4$ with the electronic structure of the parent high-temperature superconductor system BaFe$_2$As2 is carried out. It is established that in spite of the rather large value of the electron-electron correlations (local Coulomb interaction on the Co-$3d$ shell $U = 4.0$ eV, the Hund exchange interaction $J = 0.85$ eV), in the considered systems a relatively small quasiparticle mass renormalization $1.2$–$1.35$ at the Fermi level is observed. The correlation effects lead to the remarkable shift and compression of the spectrum below $-0.8$ eV. The band structure of InCo$_2$As$_2$ near the Fermi level is qualitatively similar to the previously studied BaCo$_2$As$_2$, and differs significantly from the band structure of BaFe$_2$As$_2$. In the KInCo$_4$As$_4$ system, the bands near the Fermi level resemble the band structure of BaFe$_2$As$_2$, and the Fermi surfaces have a similar topology. This indirectly points to the possibility of superconductivity in KInCo$_4$As$_4$. Also according to the results of LDA + DMFT calculations it is seen that with a rather small hole or electron doping in the KInCo$_4$As$_4$ system will experience topological Lifshitz transitions. We believe that the synthesis of the InCo$_2$As$_2$ and KInCo$_4$As$_4$ compounds considered in this paper is important for the study of superconductivity in this class of materials.