A5023258757- Topological Materials and Phenomena
- 2D Materials and Applications
- Rare-earth and actinide compounds
- Inorganic Chemistry and Materials
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Organic and Molecular Conductors Research
- Advanced Condensed Matter Physics
- Advanced Materials Characterization Techniques
- Thermal Expansion and Ionic Conductivity
Tohoku University
2022-2025
National Synchrotron Radiation Research Center
2020-2024
Spin-valley magnetic ordering is restricted to layered van der Waals type transition-metal dichalcogenides with temperatures below 55 K. Recent theoretical studies on non-van structures have predicted spin-valley polarization induced semiconducting ferromagnetic ground states, but experimental validation missing. We report high-Curie temperature (TC ~ 225 K) metallic ferromagnetism spontaneous in monolayer Cr2Se3 graphene. Angle-resolved photoemission spectroscopy (ARPES) reveals systematic...
We study the high Curie temperature ferromagnet (${\mathrm{Cr}}_{0.35}{\mathrm{Sb}}_{0.65}{)}_{2}\mathrm{Te}{}_{3}$ (${T}_{C}=192\phantom{\rule{0.16em}{0ex}}\mathrm{K}$), using $T$-dependent x-ray absorption spectroscopy (XAS), magnetic circular dichroism (XMCD), and angle-resolved photoemission (ARPES). The (25--220 K) XAS-XMCD evolution of $\mathrm{Cr}\phantom{\rule{0.16em}{0ex}}3d$ $\mathrm{Te}\phantom{\rule{0.16em}{0ex}}5p$ unoccupied site- orbital-projected states shows a systematic...
GdNi is a ferrimagnetic material with Curie temperature ${T}_{C}=69$ K which exhibits large magnetocaloric effect, making it useful for magnetic refrigerator applications. We investigate the electronic structure of by carrying out x-ray absorption spectroscopy (XAS) and circular dichroism (XMCD) at $T=25$ in phase. analyze Gd ${M}_{4,5}$-edge ($3d\ensuremath{-}4f$) Ni ${L}_{2,3}$-edge ($2p\ensuremath{-}3d$) spectra using atomic multiplet cluster model calculations, respectively. The...
We performed angle-resolved photoemission spectroscopy with micro-focused beam on a topological line-nodal compound CaSb2 which undergoes superconducting transition at the onset Tc~1.8 K, to clarify Fermi-surface topology relevant occurrence of superconductivity. found that three-dimensional hole pocket G point is commonly seen for two types single-crystalline samples fabricated by different growth conditions. On other hand, carrier-doping level estimated from position chemical potential was...
We study the electronic structure of single crystal $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$ using temperature ($T$)-dependent soft x-ray photoemission spectroscopy (PES) and natural circular dichroism (NCD) across charge-density-wave (CDW) transition at ${T}_{\mathrm{cdw}}\ensuremath{\sim}200$ K. investigate detailed changes in energy positions widths Ti $2p$ Se $3d$ core-level spectra ${T}_{\mathrm{cdw}}$. The $2p\ensuremath{-}3d$-resonant PES shows a clear character two-hole correlation...
We study the electronic structure of GdNi and HoNi, which are magnetic materials with a Curie temperature ${T}_{c}=69$ ${T}_{c}=36\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, respectively. These useful for refrigerator applications at low as they exhibit large magnetocaloric effect near ${T}_{c}$. have used hard x-ray photoemission spectroscopy (HAXPES) to investigate core-level valence-band states HoNi. HAXPES measurements Gd Ho $3d, 4d, 4p, 5p$, $4s$ spectra been compared atomic multiplet...
We study the electronic structure of single crystal CeAgSb 2 , a low T c ferromagnetic Kondo system, using synchrotron radiation photoemission spectroscopy (PES) and x-ray absorption (XAS).We have carried out Ce 5s, 5p, Sb 4d core level PES as well 4d-4f resonant valence band states .We also report behavior 5s 5p core-levels simultaneous intensity suppression core-level Ag across threshold.The spectra show typical f 0 1 features associated with behavior.The constant initial state maxima at...
Understanding the mechanism of ferromagnetism in ferromagnetic topological insulators (TIs) is a key to realize exotic time-reversal-symmetry-broken quantum phases. However, electronic states relevant are highly controversial. Here we report angle-resolved photoemission spectroscopy on (CrxSb1-x)2Te3 thin films, high-Curie-temperature (T_C) TIs, spanning non-doped (T_C=0 K) highly-doped (T_C=192 region. We found that, upon Cr doping Sb2Te3, bulk valence-band valley exhibits filling-in...