Microscopic nature of correlations in multiorbitalAFe2As2(A=K,Rb,Cs): Hund's coupling versus Coulomb repulsion

Steffen Backes, Harald O. Jeschke, Roser Valentí
2015 Physical Review B  
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 AFe_2As_2 (A= K, Rb, Cs) as well as the fictitious FrFe_2As_2 and a-axis stretched CsFe_2As_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.
more » ... 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_2As_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^*. We discuss these results in the framework of reported experimental observations.
doi:10.1103/physrevb.92.195128 fatcat:ktpy6hajnje3lpwywlqez4y7z4