A5061260628- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Superconductivity in MgB2 and Alloys
- Magnetic and transport properties of perovskites and related materials
- Inorganic Chemistry and Materials
- Diamond and Carbon-based Materials Research
- Transition Metal Oxide Nanomaterials
- Electron and X-Ray Spectroscopy Techniques
- ZnO doping and properties
- Semiconductor materials and devices
- Advanced Chemical Physics Studies
- Boron and Carbon Nanomaterials Research
- Organic and Molecular Conductors Research
- Advanced Materials Characterization Techniques
- Metal and Thin Film Mechanics
- Ga2O3 and related materials
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Graphene research and applications
- Heusler alloys: electronic and magnetic properties
- MXene and MAX Phase Materials
- Catalytic Processes in Materials Science
Okayama University
2016-2025
Okayama University of Science
2016-2025
Mitsui Chemicals (Japan)
2019
Tohoku University
1994-2018
Japan Science and Technology Agency
2008-2012
The University of Tokyo
2000-2010
Suzuki (Japan)
2009
Science and Technology Corporation (United States)
2009
Centre de Recherche en Économie et Statistique
2008-2009
Centre for Research in Engineering Surface Technology
2008-2009
High-resolution angle-resolved photoemission spectroscopy was used to study the superconducting energy gap and changes in spectral function across transition quasi-two-dimensional superconductor 2H-NbSe2. The momentum dependence of determined on different Fermi surface sheets. results indicate sheet-dependent superconductivity this low-transition temperature multiband system provide a description consistent with thermodynamic measurements anomalous de Haas-van Alphen oscillations observed...
The photoemission line shape near $(\ensuremath{\pi},0)$ in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ below ${T}_{c}$ is characterized by a sharp peak, followed at higher energy dip and hump. We study the evolution of this as function momentum, temperature, doping. find hump scales with peak persists above pseudogap state. present strong evidence that peak-dip-hump structure arises from interaction electrons collective mode wave vector...
We report measurements of the momentum dependence superconducting gap in Bi_2Sr_2CaCu_2O_{8+x} (Bi2212) with angle-resolved photoemission spectroscopy using a dense sampling Brillouin zone vicinity Fermi surface. In Y quadrant zone, where there are no complications from ghost bands caused by superlattice, we find function consistent within error bars to form cos(k_x)-cos(k_y) expected for d-wave order parameter. Similar results found X photon polarization chosen enhance main band emission...
Comparing ARPES measurements on Bi2212 with penetration depth data, we show that a description of the nodal excitations d-wave superconducting state in terms non-interacting quasiparticles is inadequate, and estimate magnitude doping dependence Landau interaction parameter which renormalizes linear T contribution to superfluid density. Furthermore, although consistent symmetry, gap underdoping cannot be fit by simple coskx-cosky form, suggests an increasing importance long range interactions...
We measure the momentm dependence of superconducting gap along Fermi surface ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$ by high resolution angle-resolved photoemission spectroscopy. The is large in vicinity $\overline{M}$ point (where $\ensuremath{\gamma}$- Cu-O bond), and small $X$ $Y(\ensuremath{\pi},\ensuremath{\pi})$ directions. However, not zero these directions, but, within our accuracy, becomes about ${10}^{\ensuremath{\circ}}$ on either side...
We show, by use of angle-resolved photoemission spectroscopy, that underdoped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ appears to have a large Fermi surface centered at $(\ensuremath{\pi},\ensuremath{\pi})$, even for samples with ${T}_{c}$ as low 15 K. No clear evidence pocket around $(\ensuremath{\pi}/2,\ensuremath{\pi}/2)$ has been found. These conclusions are based on determination the minimum gap locus in pseudogap regime...
From a detailed study, including polarization dependence, of the normal state angle-resolved photoemission spectra for ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$, we find only one ${\mathrm{CuO}}_{2}$ band related feature. All other spectral features can be ascribed either to umklapps from superlattice or ``shadow bands.'' Even though dispersion peaks looks like theory, line shape is anomalously broad and no evidence found bilayer splitting. We argue that ``dip...
Photoemission spectra of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ below ${T}_{c}$ show two features near the $(\ensuremath{\pi},0)$ point zone: a sharp peak at low energy and higher binding hump. We find that persists even as one moves towards $(0,0)$, while broad hump shows significant dispersion which correlates well with normal state dispersion. argue these are naturally explained by interaction electrons mode appears only ${T}_{c}$,...
We study the new binary intermetallic superconductor MgB(2) using high-resolution photoemission spectroscopy. The superconducting-state spectrum measured at 5.4 K shows a coherent peak with shoulder structure, in sharp contrast to that expected from simple isotropic-gap opening. can be well reproduced weighted sum of two Dynes functions gap sizes 1.7 and 5.6 meV. Temperature-dependent both gaps close bulk transition temperature. These results provide spectroscopic evidence for multiple MgB(2).
We used low-temperature ultrahigh-resolution ($360\text{ }\text{ }\ensuremath{\mu}\mathrm{e}\mathrm{V}$) photoemission spectroscopy with a laser as photon source (Laser-PES) to study the superconducting (SC) gap of an $f$-electron superconductor $\mathrm{C}\mathrm{e}\mathrm{R}{\mathrm{u}}_{2}$. The unique combination large escape depth expected from known universal behavior and extremely high-energy resolution has enabled us directly measure bulk SC for first time. present provides direct...
With a strong help of high-resolution photoemission spectroscopy we demonstrate in this paper that the large thermoelectric power observed layered cobalt oxides, such as ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{4}{\mathrm{O}}_{9},$ ${\mathrm{Na}}_{0.6}{\mathrm{CoO}}_{2},$ and ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{Co}}_{2}{\mathrm{O}}_{9},$ can be well accounted for with Boltzmann-type metallic electrical conduction. An intense peak 1.5--2 eV width was spectra its center at 1.0 below Fermi...
Within a spectral function $A(\mathbf{k},\ensuremath{\omega})$ interpretation of angle-resolved photoemission (ARPES), the intensity obeys sum rule $\ensuremath{\int}d\ensuremath{\omega}f\left(\ensuremath{\omega}\right)A(\mathbf{k},\ensuremath{\omega})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}n\left(\mathbf{k}\right)$, where $f$ is Fermi and $n\left(\mathbf{k}\right)$ momentum distribution. We show usefulness this for analyzing ARPES data. The integrated in...
The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. results show that superconducting gaps with values 5.5 and 2.2 meV open on the sigma band pi band, respectively, but both close at bulk transition temperature, providing a definitive experimental evidence for two-band superconductivity strong interband pairing interaction in MgB2. experiments validate role k-dependent electron-phonon coupling as origin multiple-gap well high temperature
Particle-hole ($p\ensuremath{-}h$) mixing is a fundamental consequence of the existence pair condensate. We present direct experimental evidence for $p\ensuremath{-}h$ in angle-resolved photoemission (ARPES) spectra superconducting state ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$. In addition to its pedagogical importance, this establishes unambiguously that gap observed ARPES associated with superconductivity.
We study the first-order Verwey transition in single-crystal ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ using high-resolution temperature-dependent (100--300 K) photoemission spectroscopy. The near-Fermi-level (${\mathit{E}}_{\mathit{F}}$) spectrum exhibits a clear gap of \ensuremath{\sim}70 meV occupied part density states (DOS) low-temperature semiconducting phase. is closed above temperature ${\mathit{T}}_{\mathit{V}}$=122 K, establishing metal-semiconductor transition. Fe 3d derived features...
Hard X-ray Photoemission spectroscopy (PES) of copper core electronic states, with a probing depth $\sim$60 \AA, is used to show that the Zhang-Rice singlet feature present in La$_2$CuO$_4$ but absent Nd$_2$CuO$_4$. Hole- and electron doping La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) Nd$_{2-x}$Ce$_x$CuO$_4$ (NCCO) result new well-screened features which are missing soft PES. Impurity Anderson model calculations establish metallic screening as its origin, strongly suppressed within 15 $\text{\AA}$...
We report bulk-sensitive hard x-ray $(h\ensuremath{\nu}=5.95\phantom{\rule{0.3em}{0ex}}\mathrm{keV})$ core-level photoemission spectroscopy (PES) of single crystal ${\mathrm{V}}_{1.98}{\mathrm{Cr}}_{0.02}{\mathrm{O}}_{3}$ and the high-${T}_{c}$ cuprate ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ (Bi2212). exhibits low binding energy ``satellites'' to V $2p$ ``main lines'' in metallic phase, which are suppressed antiferromagnetic...
The detail of electronic structures near the Fermi level in ${\text{URu}}_{2}{\text{Si}}_{2}$ has been investigated employing state-of-art laser angle-resolved photoemission spectroscopy. observation a narrow dispersive band ordered state as well its absence Rh-substituted sample strongly suggest that emergence is clear signature hidden-order transition. temperature dependence band, which appears at onset transition, invokes occurrence periodicity modification state, shown for first time by...
We have observed zero resistivity above 10 K and an onset of reduction at 25.2 in a heavily B-doped diamond film. However, the effective carrier concentration is similar to that superconducting with lower Tc. found has longer mean free path lifetime than previous report, indicating this highest Tc better crystallinity compared other films. In addition, susceptibility shows small transition 20 high quality diamond, suggesting signature superconductivity K. These results strongly suggest...
Abstract Pb-substituted La(O, F)BiS 2 (Pb-LaOFBiS ) exhibits improved superconducting properties and a resistivity anomaly around 100 K that is attributed to structural transition. We have performed temperature( T )-dependent photoelectron holography (PEH) study dopant incorporation sites the local structure change across anomaly. The PEH of Pb-LaOFBiS provided evidence for dominant Pb F: atoms are incorporated into Bi F O site. No remarkable difference in structures was observed. Across...