No Arabic abstract
We show the three-dimensional electronic structure of the Kondo lattice CeIn3 using soft x-ray angle resolved photoemission spectroscopy in the paramagnetic state. For the first time, we have directly observed the three-dimensional topology of the Fermi surface of CeIn3 by photoemission. The Fermi surface has a complicated hole pocket centred at the {Gamma}-Z line and an elliptical electron pocket centred at the R point of the Brillouin zone. Polarization and photon-energy dependent photoemission results both indicate the nearly localized nature of the 4f electrons in CeIn3, consistent with the theoretical prediction by means of the combination of density functional theory and single-site dynamical meanfield theory. Those results illustrate that the f electrons of CeIn3, which is the parent material of CeMIn5 compounds, are closer to the localized description than the layered CeMIn5 compounds.
We report on experimental data of the three-dimensional bulk Fermi surfaces of the layered strongly correlated Ca1.5Sr0.5RuO4 system. The measurements have been performed by means of hn-depndent bulk-sensitive soft x-ray angle-resolved photoemission technique. Our experimental data evinces the bulk Fermi surface topology at kz~0 to be qualitatively different from the one observed by surface-sensitive low-energy ARPES. Furthermore, stronger kz dispersion of the circle-like gamma Fermi surface sheet is observed compared with Sr2RuO4. Thus in the paramagnetic metal phase, Ca1.5Sr0.5RuO4 compound is found to have rather three-dimensional electronic structure.
The electronic structure of the Kondo lattice CeIn3 has been studied by on-resonant angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy. A weakly dispersive quasiparticle band has been observed directly with an energy dispersion of 4 meV by photoemission, implying the existence of weak hybridization between the f electrons and conduction electrons. The hybridization is further confirmed by the formation of the hybridization gap revealed by temperature-dependent scanning tunneling spectroscopy. Moreover, we find the hybridization strength in CeIn3 is much weaker than that in the more two-dimensional compounds CeCoIn5 and CeIrIn5. Our results may be essential for the complete microscopic understanding of this important compound and the related heavy-fermion systems.
Bulk-sensitive hard x-ray photoemission spectroscopy (HAXPES) reveals for as-grown epitaxial films of half-metallic ferromagnetic CrO2(100) a pronounced screening feature in the Cr 2p3/2 core level and an asymmetry in the O 1s core level. This gives evidence of a finite, metal-type Fermi edge, which is surprisingly not observed in HAXPES. A spectral weight shift in HAXPES away from the Fermi energy is attributed to single-ion recoil effects due to high energy photoelectrons. In conjunction with inverse PES the intrinsic correlated Mott-Hubbard-type electronic structure is unravelled, yielding an averaged Coulomb correlation energy Uav ~ 3.2 eV.
We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited respectively on Ag (111) and (100) substrates, and similarly doped with potassium to half-filling of the C60 lowest unoccupied molecular orbital. The Fermi surface symmetry, the bandwidth, and the curvature of the dispersion at Gamma point are different. Orientations of the C60 molecules on the two substrates are known to be the main structural difference between the two monolayers, and we present new band-structure calculations for some of these orientations. We conclude that orientations play a key role in the electronic structure of fullerides.
Pr 4f electronic states in Pr-based filled skutterudites PrT4X12(T=Fe and Ru; X=P and Sb) have been studied by high-resolution bulk-sensitive Pr 3d-4f resonance photoemission. A very strong spectral intensity is observed just below the Fermi level in the heavy-fermion system PrFe4P12. The increase of its intensity at lower temperatures is observed. We speculate that this is the Kondo resonance of Pr, the origin of which is attributed to the strong hybridization between the Pr 4f and the conduction electrons.