A5010003779- Surface and Thin Film Phenomena
- Quantum and electron transport phenomena
- Graphene research and applications
- Magnetic properties of thin films
- Topological Materials and Phenomena
- Advanced Chemical Physics Studies
- Muon and positron interactions and applications
- Physics of Superconductivity and Magnetism
- Semiconductor materials and devices
- Copper Interconnects and Reliability
- Metal and Thin Film Mechanics
- Molecular Junctions and Nanostructures
- Electronic and Structural Properties of Oxides
- Electron and X-Ray Spectroscopy Techniques
- Silicon Carbide Semiconductor Technologies
- Boron and Carbon Nanomaterials Research
- nanoparticles nucleation surface interactions
- Ammonia Synthesis and Nitrogen Reduction
- Advanced Materials Characterization Techniques
- Ion-surface interactions and analysis
- Atomic and Molecular Physics
- Semiconductor materials and interfaces
- Theoretical and Computational Physics
- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
The University of Tokyo
2016-2025
Institute for Solid State Physics and Optics
2004-2024
National Institute for Materials Science
2007-2024
International Summer School of Photography
2016
Chiba University
2008
Institut National de la Recherche Scientifique
2008
SPring-8
2005-2007
Tottori University
2007
Jawaharlal Nehru Centre for Advanced Scientific Research
2007
Saha Institute of Nuclear Physics
2007
Honeycomb structures of group IV elements can host massless Dirac fermions with non-trivial Berry phases. Their potential for electronic applications has attracted great interest and spurred a broad search new materials especially in monolayer structures. We present detailed investigation the \beta 12 boron sheet, which is borophene structure that form spontaneously on Ag(111) surface. Our tight-binding analysis revealed lattice 12-sheet could be decomposed into two triangular sublattices...
The search for metallic boron allotropes has attracted great attention in the past decades and recent theoretical works predict existence of metallicity monolayer boron. Here, we synthesize \b{eta}12-sheet on a Ag(111) surface confirm presence boron-derived bands using angle-resolved photoemission spectroscopy. Fermi is composed one electron pocket at S point pair hole pockets near X point, which supported by first-principles calculations. allotrope \b{eta}12 sheet opens way to novel physics...
Spin-polarized band structure of the three-dimensional quantum spin Hall insulator ${\text{Bi}}_{1\ensuremath{-}x}{\text{Sb}}_{x}$ $(x=0.12--0.13)$ was fully elucidated by spin-polarized angle-resolved photoemission spectroscopy using a high-yield polarimeter equipped with high-resolution electron spectrometer. Between two time-reversal-invariant points, $\overline{\ensuremath{\Gamma}}$ and $\overline{\text{M}}$, (111) surface Brillouin zone, spin-up...
A Weyl semimetal is a new state of matter that hosts fermions as quasiparticle excitations. The at zero energy correspond to points bulk-band degeneracy, called nodes, which are separated in momentum space and connected only through the crystal's boundary by an exotic Fermi arc surface state. We experimentally measure spin polarization arcs first discovered TaAs. Our data, for time, reveal arcs' spin-polarization magnitude large 80% lies completely plane surface. Moreover, we demonstrate...
Abstract 2D anisotropic Dirac cones are observed in χ 3 borophene, a monolayer boron sheet, using high‐resolution angle‐resolved photoemission spectroscopy. The centered at the X and X′ points. data also reveal that hybridization between borophene Ag(111) is very weak, which explains preservation of cones. As has been predicated to be superconductor, results may stimulate further research interest novel physics such as interplay Cooper pairs massless fermions.
We determine the band structure and spin texture of WTe2 by spin- angle-resolved photoemission spectroscopy (SARPES). With support first-principles calculations, we reveal existence polarization both Fermi arc surface states bulk pockets. Our results to be a type-II Weyl semimetal candidate provide important information understand its extremely large nonsaturating magnetoresistance.
The occupied and unoccupied in-gap electronic states of a Rh-doped SrTiO3 photocatalyst were investigated by X-ray emission spectroscopy absorption for different Rh impurity valence doping levels. An midgap Rh4+ acceptor state was found 1.5 eV below the conduction band minimum. Both Rh3+ dopants to have an donor level close maximum SrTiO3. density obtained from first-principles calculations show that all observed spectral features can be assigned substitutional at Ti site Rh:SrTiO3 is...
The topology of pure Bi is controversial because its very small (∼10 meV) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14–202 bilayer films. Using high-quality films, succeed in observing quantized bulk bands with energy separations down to ∼10 meV. Detailed analyses the phase shift confined wave functions precisely determine surface and electronic structures, which unambiguously show nontrivial topology. present results...
Abstract Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is great practical interest for developing sustainable system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the efficiency water splitting. Here we demonstrate self-organized nanocomposite material concept enhancing photocarrier separation electrochemical conversion. Mechanically robust photoelectrodes are formed...
Epitaxial Rh-doped SrTiO3 thin film photocatalysts were fabricated by pulsed laser deposition under various conditions. The oxygen pressure used during growth was found to affect the valence of Rh dopant in Rh:SrTiO3 films, reproducing known optical absorption behavior powder samples. Evaporative loss observed at low pressures and high temperatures. Cyclic voltammetry measurements a K2SO4 solution showed that is highly efficient hydrogen-producing photocathode with characteristic p-type...
The effect of iridium valence in Ir:SrTiO3 on the electronic structure and photocatalytic activity a water splitting reaction was studied. Epitaxial thin film photoelectrodes were grown with controlled Ir used to measure electrochemical efficiency Ir:SrTiO3. positions in-gap impurity levels determined by optical X-ray photoelectron spectroscopies. Comparison ab initio calculations assign observed states either Ir4+ or Ir3+ dopants SrTiO3. measurements show that Ir3+:SrTiO3 forms single...
Ca-intercalation has enabled superconductivity in graphene on SiC. However, the atomic and electronic structures that are critical for still under discussion. We find an essential role of interface between monolayer SiC substrate superconductivity. In process, at a carbon layer terminating changes to by Ca-termination (monolayer becomes bilayer), inducing more electrons than free-standing model. Then, Ca is intercalated layers, which shows with updated temperature (TC) up 5.7 K. addition,...
An unexplored material of copper boride has been realized recently in two-dimensional form at a (111) surface the
Optical measurements on highly doped single-layer epitaxial graphene reveal that the photoexcitation of charge carriers leads to an enhancement THz transmission. In this paper, results are explained in terms change carrier scattering rate due optical pump fluence and electric field.
Electron scattering in the topological surface state (TSS) of insulator ${\mathrm{Bi}}_{1.5}{\mathrm{Sb}}_{0.5}{\mathrm{Te}}_{1.7}{\mathrm{Se}}_{1.3}$ was studied using quasiparticle interference observed by scanning tunneling microscopy. It found that not only 180\ifmmode^\circ\else\textdegree\fi{} backscattering but also a wide range angles 100\ifmmode^\circ\else\textdegree\fi{}--180\ifmmode^\circ\else\textdegree\fi{} are effectively prohibited TSS. This conclusion obtained comparing...
The effects of Pb intercalation on the structural and electronic properties epitaxial single‐layer graphene grown SiC(0001) substrate are investigated using scanning tunneling microscopy (STM), noncontact atomic force microscopy, Kelvin probe (KPFM), X‐ray photoelectron spectroscopy, angle‐resolved photoemission spectroscopy (ARPES) methods. STM results show formation an ordered moiré superstructure pattern induced by atom underneath layer. ARPES measurements reveal presence two additional...
We present an enhanced method for synthesizing sheets of borophane. Despite the challenges associated with low efficiency, we discovered that incorporating hydrochloric acid into ion-exchange reaction significantly improved production yield from 20% to over 50%. After a thorough examination reaction, gained insight underlying mechanisms and found use provides two key benefits: accelerated borophene isolation high-purity products. This has potential pave way novel topological 2D materials...
We report experiments on the electrical conductivity of Al 0.3 Ga 0.7 As:Si in critical region metal-insulator transition. The electron concentration is finely controlled vicinity transition using persistent photoconductivity effect. value exponent turns out to be 1. due delocalization effect by magnetic field also studied.
Temperature and magnetic field dependence of conductivity in Bi thin films is measured compared with theories the localization Coulomb interaction between electrons. The anti-localization effect case strong spin-orbit interaction–logarithmic increase decreasing temperature–is found together other ln T term due to effect. From analysis inelastic scattering time determined vary as -1 below 1.5 K -2 above 4 being consistent temperature conductivity.
Recent experimental studies on transport phenomena in dirty metallic films are described. Results analysed with theories of localization and interaction electrons random potential.
We describe a spin- and angle-resolved photoelectron spectroscopy (SARPES) apparatus with vacuum-ultraviolet (VUV) laser (hν = 6.994 eV) developed at the Laser Synchrotron Research Center Institute for Solid State Physics, The University of Tokyo. spectrometer consists hemispherical analyzer equipped an electron deflector function twin very-low-energy-electron-diffraction-type spin detectors, which allows us to analyze vector three-dimensionally both high energy angular resolutions....
Abstract Spin–orbit interaction entangles the orbitals with different spins. The spin–orbital-entangled states were discovered in surface of topological insulators. However, spin–orbital-entanglement is not specialized states. Here, we show spin–orbital texture a state Bi(111) by laser-based spin- and angle-resolved photoelectron spectroscopy (laser-SARPES) describe three-dimensional spin-rotation effect photoemission resulting from spin-dependent quantum interference. Our model reveals...
The structure of an Al(111)3×3-Si surface was examined by combining data from positron diffraction and core-level photoemission spectroscopy. Analysis the rocking curves indicated that overlayer had a flat honeycomb lattice structure. Simulations Si spectra calculated via first principles one atoms in unit cell replaced Al atom. superstructure thus two-dimensional layer Al-embedded silicene on Al(111). locked icon Physics Subject Headings (PhySH)Electronic structureSurface & interfacial...