Mario Okawa
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View article: High throughput observation of latent images on resist using laser-based photoemission electron microscopy
High throughput observation of latent images on resist using laser-based photoemission electron microscopy Open
The rapid evolution of lithography technology necessitates faster pattern inspection methods. Here, we propose the use of laser-based photoemission electron microscopy (laser-PEEM) for high-throughput observation of latent images on an ele…
View article: Linear dichroic x-ray absorption response of Ti-Ti dimers along the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>c</mml:mi></mml:math> axis in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ti</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> upon Mg substitution
Linear dichroic x-ray absorption response of Ti-Ti dimers along the axis in upon Mg substitution Open
Corundum oxide Ti$_2$O$_3$ shows the metal-insulator transition around 400-600 K accompanying the nearest Ti$^{3+}$-Ti$^{3+}$ bond ($a_{1g}a_{1g}$ singlet state) formation along the $c$ axis. In order to clarify the hole-doping effect for …
View article: Quasi One-Dimensional Band Structure of Photoinduced Semimetal Phase of Ta<sub>2</sub>Ni<sub>1−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>Se<sub>5</sub> (<i>x</i> = 0.0 and 0.1)
Quasi One-Dimensional Band Structure of Photoinduced Semimetal Phase of Ta<sub>2</sub>Ni<sub>1−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>Se<sub>5</sub> (<i>x</i> = 0.0 and 0.1) Open
The photoinduced semimetal phase of Ta2Ni1−xCoxSe5 (x = 0.0 and 0.1) is studied by time-resolved angle-resolved photoemission spectroscopy. The observed band dispersions roughly agree with the generalized gradient approximation (GGA) calcu…
View article: Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe
Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe Open
View article: Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe
Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe Open
We report time- and angle-resolved photoemission spectroscopy on SnSe which currently attracts great interest due to its extremely high thermoelectric performance. Laser-assisted photoemission signals are observed within $\pm$20 fs of the …
View article: Valence Fluctuations in Yb(Al,Fe)B<sub>4</sub> Studied by Nanosecond-time-resolved Photoemission Spectroscopy Using Synchrotron Radiation
Valence Fluctuations in Yb(Al,Fe)B<sub>4</sub> Studied by Nanosecond-time-resolved Photoemission Spectroscopy Using Synchrotron Radiation Open
Temporal variations of valence states of the α-YbAl1−xFexB4 crystals (x = 0, 0.013, and 0.098) are experimentally examined in a nanosecond time-scale by time-resolved photoemission experiments using synchrotron radiation. The Yb 4f spectra…
View article: Electronic Structure of Sr<sub>3</sub>Fe<sub>2−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>O<sub>7−</sub><i><sub>δ</sub></i> Studied by Photoemission and X-ray Absorption Spectroscopy
Electronic Structure of Sr<sub>3</sub>Fe<sub>2−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>O<sub>7−</sub><i><sub>δ</sub></i> Studied by Photoemission and X-ray Absorption Spectroscopy Open
We have investigated the electronic structure of Sr 3 Fe 2-x Co x O 7-δ using photoemission and soft xray absorption spectroscopy (XAS).From the analysis on the O 1s, Fe 2p, and Co 2p core level photoemission spectra and the line-shape ana…
View article: Erratum: Anomalous metallic state with strong charge fluctuations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>Ti</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>16</mml:mn><mml:mo>+</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> revealed by hard x-ray photoemission spectroscopy [Phys. Rev. B <b>97</b>, 165116 (2018)]
Erratum: Anomalous metallic state with strong charge fluctuations in revealed by hard x-ray photoemission spectroscopy [Phys. Rev. B <b>97</b>, 165116 (2018)] Open
Received 8 January 2019DOI:https://doi.org/10.1103/PhysRevB.99.079901©2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMetal-insulator transitionPolaronsPhysical SystemsElectronic structureOxidesTechniquesPhotoem…
View article: Temperature-dependent valence state within the metallic phase of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>BaV</mml:mi><mml:mn>10</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>15</mml:mn></mml:msub></mml:mrow></mml:math> probed by hard x-ray photoelectron spectroscopy
Temperature-dependent valence state within the metallic phase of probed by hard x-ray photoelectron spectroscopy Open
We have studied electronic properties of BaV10O15 in the intermediate-temperature phase as well as in the high-temperature metallic phase by using hard x-ray photoemission spectroscopy (HAXPES). The V 2p HAXPES show a shift in the high-tem…
View article: Anomalous metallic state with strong charge fluctuations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>Ti</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>16</mml:mn><mml:mo>+</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> revealed by hard x-ray photoemission spectroscopy
Anomalous metallic state with strong charge fluctuations in revealed by hard x-ray photoemission spectroscopy Open
We have studied a charge-orbital driven metal-insulator transition (MIT) in hollandite-type ${\\mathrm{Ba}}_{x}{\\mathrm{Ti}}_{8}{\\mathrm{O}}_{16+\\ensuremath{\\delta}}$ by means of hard x-ray photoemission spectroscopy (HAXPES). The Ti $…
View article: Quantum valence criticality in a correlated metal
Quantum valence criticality in a correlated metal Open
We discover the experimental case of a quantum valence criticality leading to the breakdown of the Fermi liquid state.
View article: Electronic properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mn>13</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>18</mml:mn></mml:msub></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mrow><mml:mi>x</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mn>0.2</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn></mml:mrow><mml:mo>)</mml:mo></mml:math> studied using hard x-ray photoelectron spectroscopy
Electronic properties of studied using hard x-ray photoelectron spectroscopy Open
We have studied the electronic structure of Ba1−x Srx V13 O18 (x = 0,0.2,1) at different temperatures across the trimerization and charge-order transitions using hard x-ray photoemission spectroscopy (HAXPES). The V 2p HAXPES indicates V2+…
View article: Unusual valence state and metal-insulator transition in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>BaV</mml:mi><mml:mn>10</mml:mn></mml:msub><mml:mspace width="0.16em"/><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>15</mml:mn></mml:msub></mml:mrow></mml:math> probed by hard x-ray photoemission spectroscopy
Unusual valence state and metal-insulator transition in probed by hard x-ray photoemission spectroscopy Open
We have studied the electronic structure of BaV10O15 across the metal-insulator transition with V trimerization by means of hard-x-ray photoemission spectroscopy (HAXPES) and mean-field calculations. The V 2p HAXPES indicates V2.5+-V3+ cha…
View article: Coexistence of a pseudogap and a superconducting gap for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>high</mml:mtext><mml:mo>−</mml:mo><mml:msub><mml:mi>T</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math>superconductor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>La</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>CuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>studied by angle-resolved photoemission spectroscopy
Coexistence of a pseudogap and a superconducting gap for thesuperconductorstudied by angle-resolved photoemission spectroscopy Open
The relationship between the superconducting gap and the pseudogap has been the subject of controversies. In order to clarify this issue, we have studied the superconducting gap and pseudogap of the $\text{high}\ensuremath{-}{T}_{c}$ super…
View article: Hybridization gap formation in the Kondo insulator<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>YbB</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:math>observed using time-resolved photoemission spectroscopy
Hybridization gap formation in the Kondo insulatorobserved using time-resolved photoemission spectroscopy Open
A detailed low-energy electronic structure of a Kondo insulator YbB$_{12}$\nwas revealed by a synergetic combination of ultrahigh-resolution laser\nphotoemission spectroscopy (PES) and time-resolved PES. The former confirmed a\n25-meV pseu…
View article: Electronic Structure Evolution across the Peierls Metal-Insulator Transition in a Correlated Ferromagnet
Electronic Structure Evolution across the Peierls Metal-Insulator Transition in a Correlated Ferromagnet Open
Transition metal compounds often undergo spin-charge-orbital ordering due to strong electron-electron correlations. In contrast, low-dimensional materials can exhibit a Peierls transition arising from low-energy electron-phonon-coupling-in…
View article: Correction: Corrigendum: Emergent photovoltage on SmB6 surface upon bulk-gap evolution revealed by pump-and-probe photoemission spectroscopy
Correction: Corrigendum: Emergent photovoltage on SmB6 surface upon bulk-gap evolution revealed by pump-and-probe photoemission spectroscopy Open
Recent studies suggest that an exemplary Kondo insulator SmB6 belongs to a new class of topological insulators (TIs), in which non-trivial spin-polarized metallic states emerge on surface upon the formation of Kondo hybridization gap in th…
View article: Emergent photovoltage on SmB6 surface upon bulk-gap evolution revealed by pump-and-probe photoemission spectroscopy
Emergent photovoltage on SmB6 surface upon bulk-gap evolution revealed by pump-and-probe photoemission spectroscopy Open
Recent studies suggest that an exemplary Kondo insulator SmB6 belongs to a new class of topological insulators (TIs), in which non-trivial spin-polarized metallic states emerge on surface upon the formation of Kondo hybridization gap in th…