Temperature‐dependent electronic properties for 4f states in cerium mononitride

Abstract

In order to elucidate the temperature‐dependent occupancy number of Ce 4f electrons and valence state of Ce ions in cerium mononitride (CeN), we perform an ab initio calculation by using a many‐body scheme combing density functional theory with dynamical mean field theory, taking into account the spin‐orbit coupling (SOC) interaction and on‐site Coulomb repulsion between Ce 4f electrons. Results demonstrate that Ce 4f j = 5/2 and j = 7/2 manifolds undergo insulating‐metallic transition with increasing of temperature. Ce 4f‐conduction electrons hybridization, f‐f correlation, SOC interaction and final state effects yield a complicated spectrum function in CeN. Ce 4f atomic configuration transition and hybridization might be responsible for the temperature‐dependent occupancy number of Ce 4f electrons and the mixed‐valence state in CeN. A fact that localization of Ce 4f electrons, that is, 4f1 configuration or Ce3+ valence, increases with increasing of temperature could account for the experimentally observed lattice constant versus temperature data. Finally, the so‐called quasiparticle band structure is also discussed for comparison with experimental angle‐resolved photoemission spectrum.

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

“…45 This result establishes that 4f electrons are in an itinerant regime, which agrees well with the previous related work, 6,46 as well as the following occupancy discussion. As depicted in Figure 4C,D, j = 5/2 components are mainly located close to the Fermi level, however, j = 7/2 states exhibit a pseudo-gap, this picture demonstrates the insulating and metallic regimes for j = 7/2 and j = 5/2 components, 21 respectively, which agrees with the Green functions in Figure 1.…”

“…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 Kondo resonance is responsible for Peak, and peak E corresponds to the satellite peak arising from the crystal field effect of j = 5/2 manifold (Figure 4D). 21 Additionally, the satellite peaks F and G might arise from SOC splitting of j = 7/2 manifold. In fact, 4 f ‐derived feature is mainly located close to the Fermi level 45 .…”

“…6,47 As illustrated in Figure 4C,D, the orbital mixing/hybridization would be in favor of the mixing of 4f 0 and 4f 2 configurations in the 4f 1 final state. Besides the bonding and antibonding characters, 21 spin-orbit splitting also plays an important role in the complicated spectra feature of Ce 3 Al. 48…”

Lanthanide Contraction: What is Normal?

“…It is well-known in the physics community that the unit cell dimensions for CeN are much smaller than those of its neighbors LaN and PrN . This generally is attributed to partial oxidation of some Ce­(III) to Ce­(IV), and this may involve promotion of a valence electron into the conduction band of CeN . In any case, CeN has been excluded from the analysis here.…”