Izumi Hase

Superconducting Properties of CdCNi3

CdCNi 3 is a newly synthesized superconductor with T c =2.5–3.2 K. The crystal has the same perovskite-type structure as MgCNi 3 but the lattice constant is ∼1% larger than that of MgCNi 3 . For th...

Photoemission Study of the Metallic State of Lightly Electron-doped SrTiO3

Abstract The behavior of the metallic state of lightly electron-doped SrTiO3 has been studied using angle-integrated ultraviolet photoemission spectroscopy (UPS) and angle-resolved photoemission spectroscopy (ARPES). Two states in the bulk band gap of stoichiometric SrTiO3 are shown by doping electron carriers: a metallic state with a sharp Fermi cut-off and a broad state centered at ∼1.3 eV below the Fermi level. By slight oxygen exposure, the UPS spectra showed a rapid decrease in the spectral intensity of the metallic state followed by a sudden energy shift of the valence band. These changes are explained in terms of the band-bending effect due to the formation of a thick charge depletion layer when the adsorbed oxygen atoms attract the free electrons from the bulk to the surface. Normal-emission photoelectron spectra before the oxygen exposure showed that the spectral intensity of the metallic state is remarkably enhanced at the photon energy of 28 and 45 eV whereas its energy position is almost independent of the photon energy. Off-normal-emission spectra showed that the spectral intensity of the metallic state is drastically reduced with increasing emission angle. From a comparison between the calculated band structure and ARPES results, we conclude that the metallic state is qualitatively explained by the Fermi liquid behavior based on the band theory.

Low-Lying Optical Phonon Modes in the Filled Skutterudite CeRu4Sb12

The phonon dynamics of filled skutterudite CeRu 4 Sb 12 have been studied at room temperature by inelastic neutron scattering. Optical phonons associated with a large vibration of Ce atoms are obse...

Electronic state of Fe in double perovskite oxide Sr2FeWO6

The magnetic properties of double perovskite oxide Sr 2 FeWO 6 have been reported. The magnetic susceptibility and Mossbauer effect of 57 Fe show that this compound is an antiferromagnet with T N =37 K. The Mossbauer parameters below ∼20 K are the center shift of +1.2 mm/s relative to metallic iron, the quadrupole splitting of 1.9 mm/s and the hyperfine field of ∼110 kOe. The quadrupole splitting has a strong temperature dependence. From these data, we conclude that Fe in Sr 2 FeWO 6 is in the Fe 2+ high-spin state, while the hyperfine field seems to be quite small. The cell volume shows a large increase compared to other Sr 2 FeTO 6 ( T= Mo, Re, etc.), which is in the Fe 3+ high-spin state. These results suggest that these compounds have a strongly coupled charge and lattice systems.

Madelung energy of the valence-skipping compound BaBiO3

Several elements show valence skip fluctuation, for instance, Tl forms the compounds in valence states +1 and +3, and Bi forms in +3 and +5 states. This kind of fluctuation gives rise to a negative effective attractive interaction and the Kondo effect. In the compounds of valence skipping elements, the carrier doping will induce superconductivity with high critical temperature. For example, Ba

Massless Modes and Abelian Gauge Fields in Multi-Band Superconductors

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Electronic structures of Sr2RuO4 and Sr2RhO4

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Isotope Effect in Multi-Band and Multi-Channel Attractive Systems and Inverse Isotope Effect in Iron-Based Superconductors

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BANDWIDTH CONTROL IN A PEROVSKITE-TYPE 3D1-CORRELATED METAL CA1-XSRXVO3. II. OPTICAL SPECTROSCOPY

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Electronic Structure of RNiC2 (R=La, Y, and Th)

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