A5015460293- Topological Materials and Phenomena
- Surface and Thin Film Phenomena
- Quantum and electron transport phenomena
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Advanced Condensed Matter Physics
- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- Advanced Chemical Physics Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Heusler alloys: electronic and magnetic properties
- Electron and X-Ray Spectroscopy Techniques
- Advanced Materials Characterization Techniques
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- MXene and MAX Phase Materials
- Photorefractive and Nonlinear Optics
- ZnO doping and properties
- Molecular Junctions and Nanostructures
- Chalcogenide Semiconductor Thin Films
- Machine Learning in Materials Science
- Laser-Matter Interactions and Applications
- Magneto-Optical Properties and Applications
- Rare-earth and actinide compounds
National Institute for Materials Science
2020-2025
Museum of Japanese Art Yamato Bunkakan
2025
Tohoku University
2025
The University of Tokyo
2012-2021
Institute for Solid State Physics and Optics
2018
Japan Science and Technology Agency
2010-2016
Japan Atomic Energy Agency
2012
Advanced Science Research Center
2012
Kyoto University
2009-2011
Hiroshima University
2002-2007
Topological superconductors, whose edge hosts Majorana bound states or fermions that obey non-Abelian statistics, can be used for low-decoherence quantum computations. Most of the proposed topological superconductors are realized with spin-helical through proximity effect to BCS superconductors. However, such approaches difficult further studies and applications because low transition temperatures complicated hetero-structures. Here by using high-resolution spin-resolved angle-resolved...
The generation of spin-polarized electrons at room temperature is an essential step in developing semiconductor spintronic applications. To this end, we studied the electronic states a Ge(111) surface, covered with lead monolayer fractional coverage 4/3, by angle-resolved photoelectron spectroscopy (ARPES), spin-resolved ARPES and first-principles structure calculation. We demonstrate that metallic surface-state band dominant Pb 6p character exhibits large Rashba spin splitting 200 meV...
Topological insulators (TIs) host novel states of quantum matter, distinguished from trivial by the presence nontrivial conducting boundary connecting valence and conduction bulk bands. Up to date, all TIs discovered experimentally rely on either time reversal or symmorphic mirror symmetry protect massless Dirac-like states. Very recently, it has been theoretically proposed that several materials are a new type protected nonsymmorphic symmetry, where glide-mirror can exotic surface fermions...
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...
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.
Abstract Modification of the gap at Dirac point (DP) in axion antiferromagnetic topological insulator $${\hbox {MnBi}}_2 {\hbox {Te}}_4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mtext>MnBi</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> <mml:mtext>Te</mml:mtext> <mml:mn>4</mml:mn> </mml:mrow> </mml:math> and its electronic spin structure have been studied by angle- spin-resolved photoemission spectroscopy (ARPES) under laser excitation various...
Abstract A quantum spin Hall (QSH) insulator hosts topological states at the one-dimensional (1D) edge, along which backscattering by nonmagnetic impurities is strictly prohibited. Its 3D analogue, a weak (WTI), possesses similar quasi-1D confined side surfaces. The enhanced confinement could provide route for dissipationless current and better advantages applications relative to strong insulators (STIs). However, surface usually not cleavable thus hard observe. Here, we visualize of WTI...
Abstract The maximum stress minimization problem is among the most important topics for structural design. conventional gradient-based topology optimization methods require transforming original into a pseudo-problem by relaxation techniques. Since their parameters significantly influence optimization, accurately solving without using techniques expected to achieve extreme performance. This paper focuses on this challenge and investigates whether designs with more avoided concentrations can...
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...
Interference of spin-up and spin-down eigenstates depicts spin rotation electrons, which is a fundamental concept quantum mechanics accepts technological challenges for the electrical manipulation. Here, we visualize this coherent physics through laser spin- angle-resolved photoemission spectroscopy on spin-orbital entangled surface-state topological insulator. It unambiguously revealed that linearly polarized can simultaneously excite states these spin-basis are coherently superposed in...
We use spin- and angle-resolved photoemission spectroscopy (SARPES) combined with polarization-variable laser investigate the spin-orbit coupling effect under interband hybridization of Rashba spin-split states for surface alloys Bi/Ag(111) Bi/Cu(111). In addition to conventional band mapping spin-splitting, different orbital spin parts wavefucntion are directly imaged into energy-momentum space. It is unambiguously revealed that modifies character leading enriched spin-orbital entanglement...
Harnessing electron spin is crucial in developing energy-saving and high-speed devices for the next generation. In this scheme, visualizing spin-polarized electronic states aids designing new materials devices. Spin-resolved photoemission spectroscopy provides information on states. To investigate microscopic devices, spin-resolved requires spatial resolution a sub-micrometer scale. Here we show imaging-type microscopy (iSPEM) with an ultraviolet laser developed at National Institutes...
We demonstrate high-throughput evaluation of the half-metallicity Co
A pair of different surface-state and surface-resonance bands has been identified on $\text{Bi}/\text{Ge}(111)\text{\ensuremath{-}}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ by a combined experimental computational study. The wave functions the states have negligible amplitude at Bi atoms are extended over more than 20 subsurface layers. These exhibit characteristic spin structure, which is ascribed to Rashba atomic spin-orbit interaction...
We discover a pair of spin-polarized surface bands on the (111) face grey arsenic by using angle-resolved photoemission spectroscopy (ARPES). In occupied side, resembles typical nearly-free-electron Shockley states observed noble-metal surfaces. However, pump-probe ARPES reveals that traverses bulk band gap and crossing at Γ[over ¯] is topologically unavoidable. First-principles calculations well reproduce their nontrivial topology; also support are type because they arise from inversion...
We investigate the surface electronic structures of polar $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}\mathrm{MoT}{\mathrm{e}}_{2}$, Weyl semimetal candidate realized through nonpolar-polar structural phase transition, by utilizing laser angle-resolved photoemission spectroscopy combined with first-principles calculations. Two kinds domains different band dispersions are observed from a single-crystalline sample. The spin-resolved measurements further reveal that spin polarizations and...
Spin-resolved band structures of L-gap surface states on Ag(111) and Cu(111) are investigated by spin- angle-resolved photoelectron spectroscopy (SARPES) with a vacuum-ultra-violet laser. The observed spin textures the agree that expected conventional Rashba effect. parameter state is estimated quantitatively 80% Cu(111). surface-state wave function found to be predominantly even mirror-symmetry negligible odd contribution SARPES using linearly polarized light. results consistent our...
We describe a setup of time-, spin-, and angle-resolved photoemission spectroscopy (tr-SARPES) employing 10.7 eV (λ = 115.6 nm) pulse laser at 1 MHz repetition rate as probe photon source. This equipment effectively combines the technologies high-power Yb:fiber laser, ultraviolet-driven harmonic generation in Xe gas, SARPES apparatus equipped with very-low-energy-electron-diffraction spin detectors. A high (1 MHz) allows experiments space-charge effects significantly reduced, despite flux...