Electronic structure and de Haas–van Alphen frequencies in KFe₂As₂within LDA+DMFT

Abstract

Recent density functional theory (DFT) calculations for KFe 2 As 2 have been shown to be insufficient to satisfactorily describe angle-resolved photoemission (ARPES) measurements as well as observed de Haas-van Alphen (dHvA) frequencies. In the present work, we extend DFT calculations based on the fullpotential linear augmented plane-wave method by dynamical mean field theory (DFT+DMFT) to include correlation effects beyond the local density approximation. We present results for two sets of reported crystal structures. Our calculations indicate that KFe 2 As 2 is a moderately correlated metal with a mass renormalization factor of the Fe 3d orbitals between 1.6 and 2.7. Furthermore, the obtained shape and size of the Fermi surface are in good agreement with ARPES measurements and we observe some topological changes with respect to DFT calculations such as the opening of an inner hole cylinder at the Z point. As a result, our calculated dHvA frequencies differ greatly from existing DFT results and qualitatively agree with experimental data. On this basis, we argue that correlation effects are important to understand the -presently under debatenature of the superconducting state in KFe 2 As 2 .

Ab initio perspective on structural and electronic properties of iron‐based superconductors

“…In our LDA + DMFT calculations reported in Ref. (), we find that KFe 2 As 2 is a moderately to strongly correlated metal with a mass renormalization factor of the Fe orbitals between 1.6 and 2.7. The observed strong flattening of electronic bands due to the renormalization is a possible explanation for the spread of experimental results in this compound in terms of extreme sensitivity to the experimental stoichiometry.…”

“…We now move to the description of our results obtained for the hole‐doped iron‐pnictide superconductor KFe 2 As 2 (). Especially for this material, DFT calculations are insufficient to satisfactorily describe ARPES measurements as well as observed dHvA frequencies.…”

“…From our previous work, we know that correlation effects are extremely important in KFe 2 As 2 and that even the Fermi surface from pure DFT is incorrect (). At large pressures, one can, however, expect the electronic bandwidth to increase and correlation effects to diminish in consequence.…”

“…Fermi surface at k z = 0 of KFe 2 As 2 as obtained from DFT (left) and the momentum-resolved spectral function at the Fermi level as obtained from LDA + DMFT (right). Reprinted with permission from Ref [93]…”

Evolution of superconducting gap anisotropy in hole‐doped 122 iron pnictides

“…Note that while self‐energy effects seem to be less important for strong hole doping, mass renormalization appears to become even more significant, and that spin fluctuations, even though incommensurate, might persist further in hole‐doped than electron‐doped 122 compounds (). This is consistent with the finding from correlation‐induced mass enhancements (), a claimed improvement of experimental evidence and theoretical modeling through a DMFT + DFT analysis , and a detailed ARPES analysis at optimal doping (). (Recently, the enlarged density of states close but not at the Fermi level has also been suggested to explain the enhancement of correlations in K‐122 ()).…”