A. Higashiya

The prominent 5d-orbital contribution to the conduction electrons in gold

We have examined the valence-band electronic structures of gold and silver in the same column in the periodic table with nominally filled d orbitals by means of a recently developed polarization-dependent hard x-ray photoemission. Contrary to a common expectation, it is found that the 5d-orbital electrons contribute prominently to the conduction electrons in gold while the conduction electrons in silver are to some extent free-electron-like with negligible 4d contribution, which could be related to a well-known fact that gold is more stable than silver in air. The 4d electron correlation effects are found to be essential for the conduction electron character in silver.

~8?keV photoemission of the metal?insulator transition system VO2

Hard and soft x-ray photoelectron spectroscopies (called HAXPES and SXPES) were performed at ~8 and ~1.25u2009keV for the metal–insulator transitions (MIT) system VO2. From the sharp difference between HAXPES and SXPES in the O 1s spectra, it was found that the clean surface of the metal VO2 is covered with a less itinerant surface layer. Clear changes of the spectral shapes were observed in HAXPES on MIT for the V 1s, 2p, 3s, 3p and O 1s core levels. The enhanced intensity of these core levels in the low-binding-energy (EB) region of the main peak in the metal phase is due to the non-local or long range screening effects. The V 3d valence band in the metal phase is composed of coherent and incoherent parts. The prominent peak near 0.9u2009eV in the insulator phase has an incoherent tail in the high-EB region and the peak and its lower EB components are understood to have a noticeable coherent component. It is experimentally confirmed that both electron correlation and band changes induced by lattice distortion are responsible for the spectral changes on MIT in VO2.

Electron correlation in the FeSe superconductor studied by bulk-sensitive photoemission spectroscopy

We have investigated the electronic structures of recently discovered superconductor FeSe by soft-x-ray and hard-x-ray photoemission spectroscopy with high bulk sensitivity. The large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF), which is demonstrated to be a coherent quasi-particle peak. Compared with the results of the band structure calculation with local-density approximation, Fe 3d band narrowing and the energy shift of the band toward EF are found, suggesting an importance of the electron correlation effect in FeSe. The self energy correction provides the larger mass enhancement value (Z^-1=3.6) than in Fe-As superconductors and enables us to separate a incoherent part from the spectrum. These features are quite consistent with the results of recent dynamical mean-field calculations, in which the incoherent part is attributed to the lower Hubbard band.

Do all nuclei recoil on photoemission in compounds

Hard and soft x-ray photoelectron spectroscopy was performed for core and valence electrons in solid compounds containing V and O atoms. The single-nucleus recoil effects on photoelectron emission were observed in the form of recoil shifts for all core levels and the valence band in a heavy Fermion material LiV2O4, whereas such shifts were negligible in VO2 even in the high-temperature metal phase. The valence band recoil shifts of V5O9 and V2O3 metal are found to be in between. These differences in the valence band are ascribable to the difference in the relative spectral weight of the O 2p component near the Fermi level.

Electronic structure of Ce Ru 2 X 2 ( X = Si , Ge ) in the paramagnetic phase studied by soft x-ray ARPES and hard x-ray photoelectron spectroscopy

Soft and hard x-ray photoelectron spectroscopy has been performed for one of the heavy fermion system

Bulk nature of layered perovskite iridates beyond the Mott scenario: An approach from a bulk-sensitive photoemission study

mathrm{Ce}{mathrm{Ru}}_{2}{mathrm{Si}}_{2}

Charge dynamics in strongly correlated one-dimensional Cu-O chain systems revealed by inelastic x-ray scattering

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Intrinsic correlated electronic structure of CrO2 revealed by hard x-ray photoemission spectroscopy

4f

Significance of the inter-site Coulomb interaction between the O 2p and Cu 3d holes revealed by resonant inelastic x-ray scattering of Sr14Cu24O41

-localized ferromagnet

Photoemission Spectroscopy and X-ray Absorption Spectroscopy Studies of the Superconducting Pyrochlore Oxide Cd2Re2O7

mathrm{Ce}{mathrm{Ru}}_{2}{mathrm{Ge}}_{2}