Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 68: Superconductivity: Fe-based Superconductors - Theory I

TT 68.5: Talk

Wednesday, April 2, 2014, 16:15–16:30, HSZ 201

LDA+DMFT study of the iron-pnictide superconductor KFe₂As₂ — •Steffen Backes, Daniel Guterding, Harald Jeschke, and Roser Valenti — Institut für Theoretische Physik, Goethe-Universität, Frankfurt

We study the electronic structure of the iron pnictide superconductor KFe₂As₂, including electronic correlations within dynamical mean field theory. The recent theoretical studies based on density functional calculations (DFT) turned out to be unable to satisfactorily describe experimental observed properties of the electronic band structure. However, treating electronic correlations beyond the local density approximation within an LDA+DMFT (dynamical mean field theory) approach has shown to be a very effective method to overcome some of these discrepancies. Therefore, we perform a comprehensive LDA+DMFT investigation focused on features of the KFe₂As₂ compound that have not been dealt with in existing studies. We also benchmark our findings with ARPES measurements. Our results indicate that KFe₂As₂ is a moderately correlated metal, where the Fe 3d orbitals show an electron mass enhancement of a factor of about 2. We find that only when including correlations beyond DFT the shape and size of the hole Fermi surface in experiment can satisfactorily be described. Furthermore, due to correlations a topological change in the Fermi surface is induced, where compared to DFT the hole pocket at the Z point vanishes in LDA+DMFT in agreement with experiments. We also observe a strong k_z-dispersion of the middle hole cylinder around Γ along the k_z-axis , which is not seen in DFT.