Microscopic nature of correlations in multi-orbital AFe2As2 (A=K, Rb, Cs): Hund's coupling versus Coulomb repulsion

Abstract

We investigate via LDA+DMFT (local density approximation combined with dynamical mean field theory) the manifestation of correlation effects in a wide range of binding energies in the hole-doped family of Fe-pnictides $A$Fe${}_2$As${}_2$ ($A=\mathrm{K}$, Rb, Cs) as well as the fictitious FrFe${}_2$As${}_2$ and $a$-axis stretched CsFe${}_2$As${}_2$. This choice of systems allows for a systematic analysis of the interplay of Hund's coupling $J_H$ and on-site Coulomb repulsion $U$ in multi-orbital Fe-pnictides under negative pressure. With increasing ionic size of the alkali metal, we observe a non-trivial change in the iron $3d$ hoppings, an increase of orbitally-selective correlations and the presence of incoherent weight at high-binding energies that do not show the typical lower Hubbard-band behavior but rather characteristic features of a Hund's metal. This is especially prominent in $a$-stretched CsFe${}_2$As${}_2$. We also find that the coherent/incoherent electronic behavior of the systems is, apart from temperature, strongly dependent on $J_H$ and we provide estimates of the coherence scale $T^{\ast }$. We discuss these results in the framework of reported experimental observations.

13 pages, 16 figures, PRB(in press)

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• Characteristic Timescales of the Local Moment Dynamics in Hund's-metals
• The ab initio study of unconventional superconductivity in CeCoIn${}_5$ and FeSe
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• Dominant in-plane symmetric elastoresistance in CsFe2As2
• Non-trivial role of interlayer cation states in iron-based superconductors
• Enhancement of charge instabilities in Hund's metals by the breaking of rotational symmetry
• Structural, electronic, and dynamical properties of the tetragonal and collapsed tetragonal phases of KFe${}_2$As${}_2$
• Observation of an Emergent Coherent State in the Iron-Based Superconductor KFe${}_2$As${}_2$
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• Increasing stripe-type fluctuations in $A$Fe${}_2$As${}_2$ ($A$ = K, Rb, Cs) superconductors probed by ${}^{75}$As NMR spectroscopy
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• Mass enhancements and band shifts in strongly hole overdoped Fe-based pnictide superconductors: KFe${}_2$As${}_2$ and CsFe${}_2$As${}_2$
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• Orbital-selective correlations and renormalized electronic structure in LiFeAs
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• Influence of graphene on the electronic and magnetic properties of an iron(III) porphyrin chloride complex
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