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| VOLUME 100 (2014) | ISSUE 2 | PAGE 128 |
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Effect of correlations and doping on the spin susceptibility of iron pnictides: the case of
KFe2As2
S. L. Skornyakov, V. I. Anisimov, D. Vollhardt+
Institute of Metal Physics UB of the RAS, 620990 Yekaterinburg, Russia Ural Federal University, 620002 Yekaterinburg, Russia +Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany
Abstract
The temperature dependence of the paramagnetic susceptibility of the iron pnictide superconductor KFe2As2 and its connection with the spectral properties of that material is investigated by a combination of density functional theory (DFT) in the local density approximation and dynamical mean-field theory (DMFT). Unlike other iron pnictide parent compounds where the typical oxidation state of iron is 2, the formal valence of Fe in KFe2As2 is 2.5, corresponding to an effective doping with 0.5 hole per iron atom compared to, for example, BaFe2As2. This shifts the chemical potential and thereby reduces the distance between the peaks in the spectral functions of KFe2As2 and the Fermi energy as compared to BaFe2As2. The shift, which is clearly seen on the level of DFT as well as in DMFT, is further enhanced by the strong electronic correlations in KFe2As2. In BaFe2As2 the presence of these peaks results (Phys. Rev. B 86, 125124 (2012)) in a temperature increase of the susceptibility up to a maximum at  K.
While the temperature increase was observed experimentally the decrease
at even higher temperatures is outside the range of experimental
observability.
We show that in KFe2As2 the situation is different. Namely,
the reduction of the distance between the peaks and the Fermi level due
to doping shifts the maximum in the susceptibility to much lower
temperatures,
such that the decrease of the susceptibility becomes visible in experiment.
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