Structure-Dependent Phase Diagram of the Occupation Number of 4f Electrons in Cerium Monoarsenide

Abstract

In order to investigate the structure-dependent correlation strength and occupation number of 4f electrons in cerium monoarsenide (CeAs) with the NaCl-type (B1-type) and CsCl-type (B2-type) structures, respectively, we perform a first principles calculation based on a many-body method merging density functional theory with dynamical mean-field theory (DMFT). Calculation results suggest that with the increase of the lattice constants, the Ce 4f j = 7/2 manifold maintains the insulating behavior, while the j = 5/2 component undergoes the insulating → metallic → insulating and the insulating → metallic transitions, respectively, for B1-type and B2-type structures. Quasi-particle weights demonstrate that the j = 7/2 manifold is in the weakly correlated regime, and the j = 5/2 component transforms from the weakly to moderately correlated state, irrespective of the crystal structure. Ce 4f electrons transform from a slight itinerant state into a localized state for the B1-type structure. A structure-dependent phase diagram of the occupation number suggests that the occupation numbers of individual 4f n (n = 0, 1, 2, 3) configurations and Ce 4f electrons (n f) could be modulated in terms of the crystal structure and/or the lattice constant.

Ce 4f electronic spectrum function in Ce3Al intermetallic compound studied via a many‐body method

“…To a certain extent, the electronic, bonding, and valence properties are dominated by orbital hybridization. Previous reports indeed suggest that the orbital mixing/hybridization between the localized f electrons and the delocalized conduction electrons could account for the electronic structure of f ‐electron materials 22,40 . For Ce 3 Al, the hybridization functions shown in Figure 3 demonstrate that 4 f orbitals somewhat mix/hybridize with the more itinerant orbitals close to zero energy (the Fermi level).…”

“…Moreover, the coherent and dispersive bands below the Fermi level mainly arise from the conduction electrons 6,55 . The low‐lying j = 5/2 component is responsible for the three‐peaked structure around the Fermi level, 6,21 a typical signature of the strongly correlated metals 22,24 . Additionally, the bright stripes close to the binding energies of 2.3 and 4.6 eV might originate from the incoherent 4 f bands (mainly 4 f 1 configuration) and the upper Hubbard band shown in Figure 4C,D 6,56 .…”

“…The slope of the imaginary part of the self‐energy close to zero energy yields Z f 7/2 = 0.328, Z f 5/2 = 0.509 for j = 5/2, j = 7/2 components, respectively, suggesting that j = 5/2, j = 7/2 manifolds have the strongly and weakly correlated behaviors, respectively 22,35 . Besides, the ratio R = Z ( f 7/2 )/ Z ( f 5/2 ) is significantly bigger than 1, indicating that Ce 3 Al system is in the so‐called orbital‐selective localized state, 34 which is consistent with a previous work of Huang et al 6 Furthermore, the angular moment coupling scheme allows one to speculate that the jj coupling scheme is more applicable for 4 f electrons in Ce 3 Al 22,35 …”

“…6,55 The low-lying j = 5/2 component is responsible for the three-peaked structure around the Fermi level, 6,21 a typical signature of the strongly correlated metals. 22,24 Additionally, the bright stripes close to the binding energies of 2.3 and 4.6 eV might originate from the incoherent 4f bands (mainly 4f 1 configuration) and the upper Hubbard band shown in Figure 4C,D. 6,56 While the dispersive blur bands within the energy interval of −3.0 and 0.0 eV are closely related to the lower Hubbard bands in Figure 4C,D, indicating that most of Ce 4f orbitals are unoccupied.…”

“…The on‐site Coulomb repulsion and the Hund's exchange parameters are chosen to be U = 5.0 eV 26 and J = 0.8 eV, 30,31 respectively. The other computational details can be found elsewhere 22 …”