Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userManifestation of electron correlation effect in $mathrm{U}~5f$ states of uranium compounds revealed by $mathrm{U}~4d-5f$ resonant photoemission spectroscopy
133
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We have elucidated the nature of the electron correlation effect in uranium compounds by imaging the partial $mathrm{U}~5f$ density of states (pDOS) of typical itinerant, localized, and heavy fermion uranium compounds by using the $mathrm{U}~4d-5f$ resonant photoemission spectroscopy. Obtained $mathrm{U}~5f$ pDOS exhibit a systematic trend depending on the physical properties of compounds. The coherent peak at the Fermi level can be described by the band-structure calculation, but an incoherent peak emerges on the higher binding energy side ($lesssim 1~mathrm{eV}$) in the Uf pDOS of localized and heavy fermion compounds. As the $mathrm{U}~5f$ state is more localized, the intensity of the incoherent peak is enhanced and its energy position is shifted to higher binding energy. These behaviors are consistent with the prediction of the Mott metal-insulator transition, suggesting that the Hubbard-$U$ type mechanism takes an essential role in the $5f$ electronic structure of actinide materials.
rate research
Read More
The electronic structure of the antiferromagnet uranium nitride (UN) has been studied by angle resolved photoelectron spectroscopy using soft X-rays (hn=420-520 eV). Strongly dispersive bands with large contributions from the U 5f states were observed in ARPES spectra, and form Fermi surfaces. The band structure as well as the Fermi surfaces in the paramagnetic phase are well explained by the band-structure calculation treating all the U 5f electrons as being itinerant, suggesting that itinerant description of the U 5f states is appropriate for this compound. On the other hand, changes in the spectral function due to the antiferromagnetic transition were very small. The shapes of the Fermi surfaces in a paramagnetic phase are highly three-dimensional, and the nesting of Fermi surfaces is unlikely as the origin of the magnetic ordering.
We have investigated the electronic states of the uranium monochalcogenide US, which is a typical ferromagnetic uranium compound, using soft x-ray photoemission spectroscopy (SX-PES). In early ultraviolet photoemission spectroscopy studies, two peak structures of the U 5f states were observed and have been interpreted that one has an itinerant character around the Fermi level (EF) and the other located below EF has a character of localized U 5f electrons. In this study, the intrinsic bulk valence-band spectrum of US was first deduced by estimating the contribution of surface states to the valence-band spectrum using core-level photoemission spectra. We conclude that the electronic structure of US can be basically described by the itinerant nature of the U 5f electrons from comparison with theoretical valence-band spectra obtained by band-structure calculation in the local-density approximation.
We develop a theory for the electronic excitations in UPt$_3$ which is based on the localization of two of the $5f$ electrons. The remaining $f$ electron is delocalized and acquires a large effective mass by inducing intra-atomic excitations of the localized ones. The measured deHaas-vanAlphen frequencies of the heavy quasiparticles are explained as well as their anisotropic heavy mass. A model calculation for a small cluster reveals why only the largest of the different $5f$ hopping matrix elements is operative causing the electrons in other orbitals to localize.
The electronic structure of ThRu2Si2 was studied by angle-resolved photoelectron spectroscopy (ARPES) with incident photon energies of hn=655-745 eV. Detailed band structure and the three-dimensional shapes of Fermi surfaces were derived experimentally, and their characteristic features were mostly explained by means of band structure calculations based on the density functional theory. Comparison of the experimental ARPES spectra of ThRu2Si2 with those of URu2Si2 shows that they have considerably different spectral profiles particularly in the energy range of 1 eV from the Fermi level, suggesting that U 5f states are substantially hybridized in these bands. The relationship between the ARPES spectra of URu2Si2 and ThRu2Si2 is very different from the one between the ARPES spectra of CeRu2Si2 and LaRu2Si2, where the intrinsic difference in their spectra is limited only in the very vicinity of the Fermi energy. The present result suggests that the U 5f electrons in URu2Si2 have strong hybridization with ligand states and have an essentially itinerant character.
Recent calculations, concerning the magnetism of uranium in the U/Fe multilayer system have described the spatial dependence of the 5f polarization that might be expected. We have used the x-ray resonant magnetic reflectivity technique to obtain the profile of the induced uranium magnetic moment for selected U/Fe multilayer samples. This study extends the use of x-ray magnetic scattering for induced moment systems to the 5f actinide metals. The spatial dependence of the U magnetization shows that the predominant fraction of the polarization is present at the interfacial boundaries, decaying rapidly towards the center of the uranium layer, in good agreement with predictions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
