Local moment versus Kondo behavior of the 4f-electrons in rare-earth iron oxypnictides

Abstract

We consider the role played by the 4f states in the rare-earth oxyarsenides REOFeAs (RE=Ce,Pr,Nd) and the oxyphosphate CeOFeP, using a first-principles technique that combines the local density approximation and dynamical mean-field theory (LDA+DMFT). In the Pr and Nd compounds, the 4f states are located well below and above the Fermi level E_F, and essentially do not interact with the iron 3d bands located near E_F, resulting in local moment behavior. In the Ce compounds, our results reveal a qualitatively different picture, with the 3d-4f hybridization being sufficiently strong to give rise to an observable Kondo screening of the local 4f moment. Our LDA+DMFT electronic structure calculations allow us to estimate the Kondo temperature T_K for both CeOFeP and CeOFeAs. For the phosphate, the order of magnitude of our estimate is consistent with the experimental observation of T_K around 10 K. At ambient pressure, T_K is found to be negligibly small for CeOFeAs. Under applied hydrostatic pressure, we predict an exponential increase of T_K which reaches values comparable to the superconducting T_c around 40 K at pressures above 10 GPa. We conjecture that the competition between the Kondo effect and superconductivity may be at the origin of the monotonous decrease of T_c observed in CeOFeAs under pressure. We argue that the quantitative aspects of this competition are inconsistent with a weak-coupling BCS description of the superconductivity in the oxyarsenides.

6 pages, 3 figures

References in corpus (11)

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Cited by in corpus (9)

• Interplay of Rare Earth and Iron magnetism in RFeAsO with R = La, Ce, Pr, and Sm: A muon spin relaxation study and symmetry analysis
• Search for pressure induced superconductivity in CeFeAsO and CeFePO iron pnictides
• Coupling between 4f and itinerant electrons in SmFeAsO1-xFx (0.15 < x < 0.2) superconductors: an NMR study
• Evolution of the multiband RKKY interaction: Application to iron pnictides and chalcogenides
• CeFePO: f-d hybridization and quenching of superconductivity
• Evolution of Magnetism in Magnetic Topological Semimetal NdSb${}_x$Te${}_{2-x+\delta }$
• Magnetism of the Fe${}^{2+}$ and Ce${}^{3+}$ sublattices in Ce${}_2$O${}_2$FeSe${}_2$: a combined neutron powder diffraction, inelastic neutron scattering and density functional study
• Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr
• How chemical pressure affects the fundamental properties of rare-earth pnictides: an ARPES view