A5091884011- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Electronic and Structural Properties of Oxides
- Electron and X-Ray Spectroscopy Techniques
- Magnetic Properties of Alloys
- ZnO doping and properties
- Semiconductor materials and devices
- Magnetic Properties and Applications
- Heusler alloys: electronic and magnetic properties
- Surface and Thin Film Phenomena
- Rare-earth and actinide compounds
- Semiconductor Quantum Structures and Devices
- Machine Learning in Materials Science
- Semiconductor materials and interfaces
- Advanced Chemical Physics Studies
- Quantum and electron transport phenomena
- Chalcogenide Semiconductor Thin Films
- X-ray Diffraction in Crystallography
- Multiferroics and related materials
- X-ray Spectroscopy and Fluorescence Analysis
- Corporate Taxation and Avoidance
- 2D Materials and Applications
Osaka University
2001-2025
High Energy Accelerator Research Organization
2015-2024
Aichi Gakuin University
2024
National Institute for Materials Science
2003-2023
The Graduate University for Advanced Studies, SOKENDAI
2008-2023
Toyota Motor Corporation (Japan)
2023
Monash University
2023
Materials Science & Engineering
2023
The University of Tokyo
2002-2019
Kavli Institute for the Physics and Mathematics of the Universe
2019
We study superconducting FeSe $({T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}9\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ exhibiting the tetragonal-orthorhombic structural transition $({T}_{\mathrm{s}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}90\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ without any antiferromagnetic ordering, by utilizing angle-resolved photoemission spectroscopy. In detwinned orthorhombic state, energy position of...
The ultrathin ${\mathrm{SiO}}_{2}/\mathrm{S}\mathrm{i}(100)$ interface has been investigated by extensive high-resolution angle-resolved photoemission measurements of the Si $2p$ core levels. polar angle dependence intensities are measured in detail for different suboxide $({\mathrm{Si}}^{1+},$ ${\mathrm{Si}}^{2+},$ and ${\mathrm{Si}}^{3+})$ components originating from transition layers at interface. depth distribution species is quantitatively analyzed a simple electron attenuation scheme....
Strong spin-orbit coupling fosters exotic electronic states such as topological insulators and superconductors, but the combination of strong electron-electron interactions is just beginning to be understood. Central this emerging area are 5d transition metal iridium oxides. Here, in pyrochlore iridate Pr2Ir2O7, we identify a non-trivial state with single-point Fermi node protected by cubic time-reversal symmetries, using angle-resolved photoemission spectroscopy first-principles...
We investigate the two-dimensional (2D) highly spin-polarized electron accumulation layers commonly appearing near surface of n-type polar semiconductors BiTeX (X = I, Br, and Cl) by angular-resolved photoemission spectroscopy. Due to polarity strong spin-orbit interaction built in bulk atomic configurations, quantized conduction-band subbands show giant Rashba-type spin-splitting. The characteristic 2D confinement effect is clearly observed also valence-bands down binding energy 4 eV....
Size-induced suppression of permittivity in perovskite thin films is a fundamental problem that has remained unresolved for decades. This size-effect issue becomes increasingly important due to the integration nanofilms into high-κ capacitors, as well concerns intrinsic size effects may limit their device performance. Here, we report new approach produce robust nanodielectrics using nanosheet (Ca2Nb3O10), class nanomaterials derived from layered compounds by exfoliation. By solution-based...
The chiral crystal is characterized by a lack of mirror symmetry and inversion center, resulting in the inequivalent right- left-handed structures. In noncentrosymmetric structure, spin momentum electrons are expected to be locked reciprocal space with help spin-orbit interaction. To reveal textures crystals, we investigate electronic structure p-type semiconductor, elemental tellurium, simplest using spin- angle-resolved photoemission spectroscopy. Our data demonstrate that highest valence...
Determination of crystal system and space group in the initial stages structure analysis forms a bottleneck material science workflow that often requires manual tuning. Herein we propose machine-learning (ML)-based approach for classification based on powder X-ray diffraction (XRD) patterns as proof concept using simulated patterns. Our tree-ensemble-based ML model works with nearly or over 90% accuracy classification, except triclinic cases, 88% five candidates. We also succeeded...
Stacked and single-layered lepidocrocite-type titanium dioxides (hereafter denoted as stacked TiO2's, respectively) have been investigated by using first-principles calculations within density functional theory. The crystal structures, electronic dielectric properties, mechanical properties studied. validity of the present theory was confirmed reproducing experimental known bulk TiO2 polymorphs (rutile anatase). As for a TiO2, optimized structural parameters agree well with reported data an...
In situ thickness-dependent photoemission spectroscopy (PES) has been performed on SrRuO3 (SRO) layers deposited SrTiO3 substrates to study the structure-induced evolution of electronic structure. The PES spectra showing existence two critical film thicknesses reveal that a metal-insulator transition occurs at thickness 4–5 monolayers (ML) and Ru 4d-derived states around Fermi level (EF) saturates about 15 ML. observed spectral behavior well matches electric magnetic properties surface...
Ferromagnetic nanoscale zinc-blende MnAs dots were successfully fabricated on a sulfur-passivated GaAs (001) surface by molecular-beam epitaxy. Transmission electron microscopy and selected area diffraction showed that the crystalline structure was not same as of bulk with NiAs-type hexagonal structure, but type. In in situ photoemission spectroscopy dots, Fermi edge clearly observed Mn 3d partial density states similar to diluted ferromagnetic semiconductor Ga1−xMnxAs, which also supports...
We have investigated the doping and temperature dependences of pseudogap superconducting gap in single-layer cuprate La2-xSrxCuO4 by angle-resolved photoemission spectroscopy. The results clearly exhibit two distinct energy scales, namely, around (pi, 0) magnitude Delta* node characterized d-wave order parameter Delta0. In comparison with Bi2212 having higher Tc's, Delta0 is smaller, while T* are similar. This result suggests that approximately material-independent properties a single CuO2...
The nature of the pseudogap (PG) in high transition temperature (high Tc) superconducting cuprates has been a major issue condensed matter physics. It is still unclear whether Tc superconductivity can be universally associated with PG formation. Here we provide direct evidence existence phase via angle-resolved photoemission spectroscopy another family superconductor, iron pnictides. Our results reveal composition-dependent formation multiband electronic structure BaFe2(As1−xPx)2. develops...
In order to examine what extent the rigid-band-like electron doping scenario is applicable transition metal-substituted Fe-based superconductors, we have performed angle-resolved photoemission spectroscopy studies of $\mathrm{Ba}({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}{)}_{2}{\mathrm{As}}_{2}$ (Ni-122) and $\mathrm{Ba}({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{x}{)}_{2}{\mathrm{As}}_{2}$ (Cu-122), compared results with...
In the hole-doped cuprates, a small amount of carriers suppresses antiferromagnetism and induces superconductivity. electron-doped on other hand, superconductivity appears only in narrow range high electron concentration ($\sim$ doped Ce content) after reduction annealing, strong antiferromagnetic (AFM) correlation persists superconducting phase. Recently, Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$ (PLCCO) bulk single crystals annealed by "protect annealing" method showed $T_c$ $\sim$ 27 K for...
We present a new compact instrument designed for scanning transmission X-ray microscopy. It has piezo-driven linear stages, making it small and light. Optical components from the virtual source point to detector are located on single optical table, resulting in portable that can be operated at general-purpose spectroscopy beamline without requiring any major reconstruction. Careful consideration been given solving vibration problem common high-resolution microscopy, so as not affect spatial...
We present an angle-resolved photoemission study of the electronic structure three-dimensional pyrochlore iridate Nd2Ir2O7 through its magnetic metal-insulator transition. Our data reveal that metallic has a quadratic band, touching Fermi level at Gamma point, similarly to Pr2Ir2O7. The node state is, therefore, common feature phase iridates. Upon cooling below transition temperature, this compound exhibits gap opening with energy shift quasiparticle peaks like band insulator. are strongly...
Core losses of amorphous and nanocrystalline soft magnetic ribbons with a range saturation magnetostriction constants (${\ensuremath{\lambda}}_{\mathrm{s}}$) from near zero to $+38\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ have been investigated experimentally complementary micromagnetic simulations in order clarify the effect on excess loss, i.e., core loss component unaccounted for by hysteresis classical eddy-current losses. The at 400 Hz peak polarization 1.0 T...
We have constructed a high-resolution synchrotron-radiation angle-resolved photoemission (ARPES) spectrometer combined with combinatorial laser molecular-beam epitaxy (laser MBE) thin film growth system in order to investigate the electronic structure of transition metal oxide films. An ARPES GAMMADATA SCIENTA SES-100 was selected for high-throughput and high-energy angular-resolution measurements. A total energy resolution 6.3 meV momentum (an angular) 0.02 Å−1 (0.2°) were obtained at...
We have investigated change in the electronic structures of atomically controlled ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ (LSMO) thin films as a function hole-doping levels $(x)$ terms vacuo photoemission spectroscopy (PES) and x-ray absorption (XAS) measurements. The PES measurements on well-ordered surface high-quality epitaxial LSMO enable us to reveal their intrinsic structures, especially structure near Fermi level $({E}_{F})$. found that overall...
We have investigated magnetic and magneto-optical properties of two-dimensional (2D) ${\mathrm{Ti}}_{0.8}{\mathrm{Co}}_{0.2}{\mathrm{O}}_{2}$ nanosheet, a new nanosized titanium oxide derived from layered titanates by exfoliation. Despite heavy doped 2D system in the dielectric ground, multilayer films nanosheets exhibit room-temperature ferromagnetism with moment $1.4{\ensuremath{\mu}}_{B}∕\mathrm{Co}$. also observe robust circular dichroism near absorption edge at...
Photoemission spectroscopy is used to investigate the electronic structure of newly discovered iron-based superconductors LaFeAsO 1- x F and LaFePO . Line shapes Fe 2 p core-level spectra suggest an itinerant character 3 d electrons. The valence-band are generally consistent with band-structure calculations except for shifts -derived peaks toward Fermi level. From taken in → core-absorption region, we have obtained experimental partial density states, explained it terms a calculation...
Abstract An important challenge in current microelectronics research is the development of techniques for making smaller, higher‐performance electronic components. In this context, fabrication and integration ultrathin high‐ κ dielectrics with good insulating properties an issue. Here, we report on a rational approach to produce high‐performance nanodielectrics using one‐nanometer‐thick oxide nanosheets as building block. titano niobate (TiNbO 5 , Ti 2 NbO 7 14 ), octahedral distortion...
We have performed angle-resolved photoemission and core-level x-ray studies of the single-layer cuprate ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2\ensuremath{-}x}{\mathrm{La}}_{x}\mathrm{Cu}{\mathrm{O}}_{6+\ensuremath{\delta}}$ (Bi2201) revealed doping evolution electronic structure from lightly doped to optimally regions. observed formation dispersive quasiparticle band, Fermi ``arc'' into surface, shift chemical potential with hole as in other cuprates. The Bi2201 is similar that...