A5083628139- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Electron and X-Ray Spectroscopy Techniques
- Iron-based superconductors research
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Advanced Chemical Physics Studies
- Inorganic Chemistry and Materials
- Magnetic Properties of Alloys
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Materials Characterization Techniques
- Magnetic properties of thin films
- Transition Metal Oxide Nanomaterials
- X-ray Diffraction in Crystallography
- Surface and Thin Film Phenomena
- Crystallization and Solubility Studies
- Ga2O3 and related materials
- Catalysis and Oxidation Reactions
- Semiconductor materials and interfaces
- Magnetism in coordination complexes
- Nuclear Materials and Properties
- Heusler alloys: electronic and magnetic properties
- Organic and Molecular Conductors Research
- Quantum and electron transport phenomena
Osaka University
2015-2024
SPring-8
2014-2024
Spintronics Research Network of Japan
2019
Graduate School USA
2017
Toyon (United States)
2017
Osaka Research Institute of Industrial Science and Technology
2015
Nippon Soken (Japan)
2010
Nagoya University
2005
Chonnam National University
2003
The University of Tokyo
1994-1998
We propose a computational scheme for the ab initio calculation of Wannier functions (WFs) correlated electronic materials. The full-orbital Hamiltonian H is projected into WF subspace defined by physically most relevant partially filled bands. H^{WF} obtained in this way, with interaction parameters calculated constrained LDA orbitals, used as an setup correlation problem, which can then be solved many-body techniques, e.g., dynamical mean-field theory (DMFT). In such calculations...
We report high-resolution high-energy photoemission spectra together with parameter-free $\mathrm{L}\mathrm{D}\mathrm{A}+\mathrm{D}\mathrm{M}\mathrm{F}\mathrm{T}$ (local density approximation $+$ dynamical mean-field theory) results for ${\mathrm{S}\mathrm{r}}_{1\ensuremath{-}x}{\mathrm{C}\mathrm{a}}_{x}{\mathrm{V}\mathrm{O}}_{3}$, a prototype $3{d}^{1}$ system. In contrast to earlier investigations the bulk are found be insensitive $x$. The good agreement between experiment and theory...
The interface between LaAlO3 and SrTiO3 hosts a two-dimensional electron system of itinerant carriers, although both oxides are band insulators. Interface ferromagnetism coexisting with superconductivity has been found attributed to local moments. Experimentally, it established that Ti 3d electrons confined the interface. Using soft x-ray angle-resolved resonant photoelectron spectroscopy we have directly mapped states in k-space. Our data demonstrate charge dichotomy. A mobile fraction...
We report on the excellent performance of a newly constructed soft x-ray helical undulator beamline BL25SU SPring-8 for photon energies 500–1800 eV. The full was designed to perform very high resolution spectroscopy solids with using brilliance, highly circularly polarized radiation. grazing incidence monochromator employs varied-line-spacing plane gratings which operate in convergent light from spherical mirror and focuses monochromatic onto exit slit. A resolving power excess 15 000...
We present the first observation of a prominent quasiparticle peak in photoemission spectrum metallic phase V2O3 and report new spectral calculations that combine local-density approximation with dynamical mean-field theory (using quantum Monte Carlo simulations) to show development such distinct decreasing temperature. The experimental width weight are significantly larger than theory.
We have investigated the chemical distributions and local electronic structure of potential diluted magnetic semiconductor Ge0.94Mn0.06 single crystals using scanning photoelectron microscopy (SPEM), x-ray absorption spectroscopy (XAS), photoemission (PES). The SPEM image shows stripe-shaped microstructures, which arise from phase separation between Mn-rich Mn-depleted phases. Mn 2p XAS that ions in region are divalent high-spin Mn2+ states but they do not form metallic clusters. 3d PES...
We report temperature-dependent redistribution of spectral weight in photoemission spectra ${\mathrm{La}}_{0.6}$${\mathrm{Sr}}_{0.4}$${\mathrm{MnO}}_{3}$ over a wide energy range several eV. attribute this to change the electron correlation strength induced by changing degree ferromagnetic order with temperature. discuss relationship between close Fermi level and unusual transport properties. \textcopyright{} 1996 The American Physical Society.
The quasi-one-dimensional conductor ${\mathrm{BaVS}}_{3}$ exhibits successive phase transitions at \ensuremath{\sim}240 K (linear chains to zigzag chains), \ensuremath{\sim}70 (metallic semiconducting), and \ensuremath{\sim}35 (paramagnetic antiferromagnetic). We have made high-resolution ultraviolet-photoemission-spectroscopy (UPS), x-ray-photoemission-spectroscopy, electrical-resistivity, magnetic-susceptibility measurements on ${\mathrm{BaVS}}_{3}$. UPS spectra near the Fermi level of...
Studying the antiferromagnetic phase of Hubbard model by dynamical mean-field theory, we observe striking differences with static (Hartree-Fock) mean field: The Slater band is strongly renormalized and spectral weight transferred to spin-polaron sidebands. Already for intermediate values interaction $U$ overall bandwidth larger than in Hartree-Fock field gap considerably smaller. Such survive any renormalization $U$. Our photoemission experiments Cr-doped ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$...
We have examined the valence-band electronic structures of gold and silver in same column periodic table with nominally filled d orbitals by means a recently developed polarization-dependent hard x-ray photoemission. Contrary to common expectation, it is found that 5d-orbital electrons contribute prominently conduction gold, while are some extent free-electron-like negligible 4d contribution, which could be related well-known fact more stable than air. The electron correlation effects...
We report the Fermi surfaces of superconductor ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ and nonsuperconductor ${\mathrm{Sr}}_{1.8}{\mathrm{Ca}}_{0.2}{\mathrm{RuO}}_{4}$ probed by bulk-sensitive high-energy angle-resolved photoemission. It is found that there one square-shaped hole-like, electron-like, circle-shaped electron-like surface in both compounds. These results provide direct evidence for nesting instability giving rise to magnetic fluctuations. Our study clarifies electron correlation...
Sm-based heavy-fermion compound ${\mathrm{SmOs}}_{4}{\mathrm{Sb}}_{12}$ has been investigated by soft x-ray ($h\ensuremath{\nu}=1070--1600\text{ }\text{ }\mathrm{eV}$) and hard (HX; $h\ensuremath{\nu}=7932\text{ spectroscopy. The HX photoemission spectroscopy clearly demonstrates that the strongly mixed-valence state coexist in bulk. It is found Sm valence decreases below 100 K, indicating Kondo coherence develops with approaching proposed temperature. Our theoretical analyses suggest origin...
We identify a satellite structure at $\ensuremath{-}3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in the photoemission spectra of layered perovskite ${\mathrm{Sr}}_{2}\mathrm{Ru}{\mathrm{O}}_{4}$ as lower Hubbard band. To this end we use state-of-the-art local-density approximation plus dynamical mean-field theory (LDA+DMFT) basis Wannier functions to compute spectral and quasiparticle dispersion ${\mathrm{Sr}}_{2}\mathrm{Ru}{\mathrm{O}}_{4}$, then compare results with newly measured...
We have synthesized a new spinel oxide LiRh2O4 with mixed-valent configuration of Rh3+ and Rh4+. At room temperature, it is paramagnetic metal, but on cooling, metal-insulator transition occurs valence bond solid state formed below 170 K. argue that the formation promoted by band Jahn-Teller at 230 K resultant confinement t_{2g} holes within xy band. The instability also responsible for observed enhanced thermoelectric power in orbital-disordered phase above
In this study, we investigate the bulk electronic structure of Pb-substituted ${\mathrm{LaO}}_{0.5}{\mathrm{F}}_{0.5}{\mathrm{BiS}}_{2}$ single crystals, using two types hard x-ray spectroscopy. High-energy-resolution fluorescence-detected absorption spectroscopy revealed a spectral change at low temperatures. Using density functional theory (DFT) simulations, find that temperature-induced originates from structural phase transition, similar to pressure-induced transition in...
By use of high-resolution soft X-rays, intrinsic temperature dependences bulk Yb 4f photoelectron spectra were obtained for fractured surfaces high-purity YbAl 3 single crystals. The not only 13 but also 12 final states are analyzed by noncrossing approximation (NCA) calculation the f 14 , and initial based on impurity Anderson model (SIAM). In order to consistently interpret both states, however, it is found that a constant set parameters hybridization strength Δ, bare energy ε electron...
Soft and hard x-ray photoelectron spectroscopy has been performed for one of the heavy fermion system $\mathrm{Ce}{\mathrm{Ru}}_{2}{\mathrm{Si}}_{2}$ a $4f$-localized ferromagnet $\mathrm{Ce}{\mathrm{Ru}}_{2}{\mathrm{Ge}}_{2}$ in paramagnetic phase. The three-dimensional band structures Fermi surface shapes have determined by soft $h\ensuremath{\nu}$-dependent angle-resolved spectroscopy. differences topology non-$4f$ electronic between are qualitatively explained band-structure calculation...
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 $\text{Fe}\text{ }3d$ spectral weight is located in vicinity Fermi level $({E}_{F})$, which demonstrated to be a coherent quasiparticle peak. Compared results band-structure calculation local-density approximation, band narrowing energy shift toward ${E}_{F}$ are found, suggesting an importance electron...
Electronic structures of Sr_2FeMoO_6 (SFMO) and Ba_2FeMoO_6 (BFMO) double perovskites have been investigated using the Fe 2p->3d resonant photoemission spectroscopy (PES) Cooper minimum in Mo 4d photoionization cross section. The states close to Fermi level are found strongly mixed Mo-Fe t_{2g} character, suggesting that valence is far from pure 3+. 2p_{3/2} XAS spectra indicate mixed-valent Fe^{3+}-Fe^{2+} configurations, larger Fe^{2+} component for BFMO than SFMO, a kind exchange...
We have studied the low-energy electronic structure of a Kondo insulator ${\mathrm{YbB}}_{12}$ by high-resolution photoemission spectroscopy. A ``Kondo peak'' is observed $\ensuremath{\sim}25$ meV below Fermi level, which agrees well with temperature, whereas gap at level found much smaller, indicating that magnetic properties higher temperatures ( $\ensuremath{\gtrsim}$75 K) are indeed determined effect in spite formation lower temperatures. renormalized band picture presented to describe...
“Bulk-sensitive” Ce 3 d -4 f resonance photoemission (RPES) with an unprecedentedly high resolution has revealed a clear difference of bulk 4 spectral weights heavy fermion system CeRu 2 Si and Ge in the region tail Kondo peak its spin-orbit partner. The significant both materials is strong contrast to mutually similar “surface-sensitive” RPES. obtained bulk-sensitive spectra are well reproduced by single impurity model. Consideration crystalline electric field splitting important for...
Soft x-ray excited angle-resolved photoemission spectroscopy (ARPES) is performed for the valence bands of quasi-one-dimensional ${\mathrm{V}}_{6}{\mathrm{O}}_{13}$ and $\mathrm{Sr}\mathrm{Cu}{\mathrm{O}}_{2}$ in order to reveal behavior strongly correlated $\mathrm{V}\phantom{\rule{0.2em}{0ex}}3d$ $\mathrm{Cu}\phantom{\rule{0.2em}{0ex}}3d$ states. The resonance enhancement state $\mathrm{V}\phantom{\rule{0.2em}{0ex}}2p$ core excitation high photoionization cross section states compared with...
We present high-resolution bulk-sensitive photoemission spectra of ${({\mathrm{V}}_{1\ensuremath{-}x}{M}_{x})}_{2}{\mathrm{O}}_{3}$ $(M=\mathrm{Cr},\mathrm{Ti})$. The measurements were made for the paramagnetic metal (PM), insulator (PI), and antiferromagnetic (AFI) phases with samples $x=0$, 0.012, 0.028 Cr doping $x=0.01$ Ti doping. In PM phase, we observe a prominent quasiparticle peak in general agreement theory, which combines dynamical mean-field theory local density approximation...