10,832 results on '"Ueda, K."'
Search Results
2. Quantum Phase Transition of Organic Spin Liquid Tuned by Mixing Counterions
- Author
-
Ueda, K., Fujiyama, S., and Kato, R.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
We found a plateau in the magnitude of the isolated magnetic moments as a function of the anisotropy of the transfer integral (t'/t) in the gapless quantum spin liquid (QSL) phase of an S=1/2 triangular lattice molecular solid X[Pd(dmit)2]2 (dmit = 1,3-dithiole-2-thione-4,5-dithiolate), accomplished by a fine-tuning of t'/t through the mixing of cations, X. In contrast, the magnetic susceptibility at the lowest temperature in the QSL phase parametrized by t'/t evinces an unconventional suppression approaching the quantum phase transition, implying significant critical fluctuations., Comment: 6 pages, 5 figures
- Published
- 2023
3. A multiple scattering theoretical approach to time delay in high energy core-level photoemission of heteronuclear diatomic molecules
- Author
-
Tamura, Y., Yamazaki, K., Ueda, K., and Hatada, K.
- Subjects
Physics - Chemical Physics ,Physics - Atomic and Molecular Clusters - Abstract
We present analytical expressions of momentum-resolved core-level photoemission time delay in a molecular frame of a heteronuclear diatomic molecule upon photoionization by a linearly polarized soft x-rays attosecond pulse. For this purpose, we start to derive a general expression of photoemission time delay based on the first order time dependent perturbation theory within the one electron and single channel model in the fixed-in-space system (atoms, molecules and crystals) and apply it to the core-level photoemission within the electric dipole approximation. By using multiple scattering theory and applying series expansion, plane wave and muffin-tin approximations, the core-level photoemission time delay $t$ is divided into three components, $t_{\rm abs}$, $t_{\rm path}$ and $t_{\rm sc}$, which are atomic photoemission time delay, delays caused by the propagation of photoelectron among the surrounding atoms and the scattering of photoelectron by them, respectively. We applied single scattering approximation to $t_{\rm path}$ and obtained $t_{\rm path}^{(1)}(k,\theta)$ with polarization vector parallel to the molecular axis for a heteronuclear diatomic molecule, where $\theta$ is the angle of measured photoelectron from the molecular axis. $t$ is approximated well with this simplified expression $t_{\rm path}^{(1)}(k,\theta)$ in the high energy regime ($k\gtrsim 3.5\,\, {\rm a.u.}^{-1}$), and the validity of this estimated result is confirmed by comparing it with multiple scattering calculations for C 1$s$ core-level photoemission time delay of CO molecules. $t_{\rm path}^{(1)}(k,\theta)$ shows characteristic dependence on $\theta$, it becomes zero at $\theta=0$, exhibits EXAFS type oscillation with $2kR$ at $\theta=\pi$, where $R$ is the bondlength, and gives just the travelling time of photoelectron from the absorbing atom to the neighbouring atom at $\theta=\pi/2$., Comment: 7 pages, 2 figures
- Published
- 2022
- Full Text
- View/download PDF
4. Investigating charge-up and fragmentation dynamics of oxygen molecules after interaction with strong X-ray free-electron laser pulses
- Author
-
Kastirke, G, Ota, F, Rezvan, DV, Schöffler, MS, Weller, M, Rist, J, Boll, R, Anders, N, Baumann, TM, Eckart, S, Erk, B, De Fanis, A, Fehre, K, Gatton, A, Grundmann, S, Grychtol, P, Hartung, A, Hofmann, M, Ilchen, M, Janke, C, Kircher, M, Kunitski, M, Li, X, Mazza, T, Melzer, N, Montano, J, Music, V, Nalin, G, Ovcharenko, Y, Pier, A, Rennhack, N, Rivas, DE, Dörner, R, Rolles, D, Rudenko, A, Schmidt, Ph, Siebert, J, Strenger, N, Trabert, D, Vela-Perez, I, Wagner, R, Weber, Th, Williams, JB, Ziolkowski, P, Schmidt, L Ph H, Czasch, A, Tamura, Y, Hara, N, Yamazaki, K, Hatada, K, Trinter, F, Meyer, M, Ueda, K, Demekhin, Ph V, and Jahnke, T
- Subjects
Physical Sciences ,Chemical Sciences ,Atomic ,Molecular and Optical Physics ,Physical Chemistry ,Chemical Physics - Abstract
During the last decade, X-ray free-electron lasers (XFELs) have enabled the study of light-matter interaction under extreme conditions. Atoms which are subject to XFEL radiation are charged by a complex interplay of (several subsequent) photoionization events and electronic decay processes within a few femtoseconds. The interaction with molecules is even more intriguing, since intricate nuclear dynamics occur as the molecules start to dissociate during the charge-up process. Here, we demonstrate that by analyzing photoelectron angular emission distributions and kinetic energy release of charge states of ionic molecular fragments, we can obtain a detailed understanding of the charge-up and fragmentation dynamics. Our novel approach allows for gathering such information without the need of complex ab initio modeling. As an example, we provide a detailed view on the processes happening on a femtosecond time scale in oxygen molecules exposed to intense XFEL pulses.
- Published
- 2022
5. Time-resolved chiral X-Ray photoelectron spectroscopy with transiently enhanced atomic site-selectivity: a Free Electron Laser investigation of electronically excited fenchone enantiomers
- Author
-
Faccialà, D., Devetta, M., Beauvarlet, S., Besley, N., Calegari, F., Callegari, C., Catone, D., Cinquanta, E., Ciriolo, A. G., Colaizzi, L., Coreno, M., Crippa, G., De Ninno, G., Di Fraia, M., Galli, M., Garcia, G. A., Mairesse, Y., Negro, M., Plekan, O., Geetha, P. Prasannan, Prince, K. C., Pusala, A., Stagira, S., Turchini, S., Ueda, K., You, D., Zema, N., Blanchet, V., Nahon, L., Powis, I., and Vozzi, C.
- Subjects
Physics - Chemical Physics - Abstract
Chiral molecules are widespread in nature, playing a fundamental role in bio-chemical processes and in the origin of life itself. The observation of dynamics in chiral molecules is crucial for the understanding and control of the chiral activity of photo-excited states. One of the most promising techniques for the study of photo-excited chiral systems is time-resolved photoelectron circular dichroism (TR-PECD), which offers an intense and sensitive probe for vibronic and geometric molecular structure as well as electronic structures, and their evolution on a femtosecond timescale. However, the non-local character of the PECD effect, which is imprinted during the electron scattering off the molecule, makes the interpretation of TR-PECD experiments challenging. In this respect, core-photoionization is known to allow site- and chemical-sensitivity to photelectron spectroscopy. Here we demonstrate that TR-PECD utilising core-level photoemission enables probing the chiral electronic structure and its relaxation dynamics with atomic site sensitivity. Following UV pumped excitation to a 3s Rydberg state, fenchone enantiomers (C 10 H 16 O) were probed on a femtosecond scale using circularly polarized soft X-ray light pulses provided by the free-electron laser FERMI. C 1s binding energy shifts caused by the redistribution of valence electron density in this 3s-valence-Rydberg excitation allowed us to measure transient PECD chiral responses with an enhanced C-atom site-selectivity compared to that achievable in the ground state molecule. These results represent the first chemical-specific and site-specific, enantio-sensitive observations on the electronic structure of a photo-excited chiral molecule and pave the way towards chiral femtochemistry probed by core-level photoemission.
- Published
- 2022
- Full Text
- View/download PDF
6. Spin-Orbit Torque Switching of Noncollinear Antiferromagnetic Antiperovskite Manganese Nitride Mn$_3$GaN
- Author
-
Hajiri, T., Matsuura, K., Sonoda, K., Tanaka, E., Ueda, K., and Asano, H.
- Subjects
Condensed Matter - Materials Science - Abstract
Noncollinear antiferromagnets have promising potential to replace ferromagnets in the field of spintronics as high-density devices with ultrafast operation. To take full advantage of noncollinear antiferromagnets in spintronics applications, it is important to achieve efficient manipulation of noncollinear antiferromagnetic spin. Here, using the anomalous Hall effect as an electrical signal of the triangular magnetic configuration, spin-orbit torque switching with no external magnetic field is demonstrated in noncollinear antiferromagnetic antiperovskite manganese nitride Mn$_3$GaN at room temperature. The pulse-width dependence and subsequent relaxation of Hall signal behavior indicate that the spin-orbit torque plays a more important role than the thermal contribution due to pulse injection. In addition, multistate memristive switching with respect to pulse current density was observed. The findings advance the effective control of noncollinear antiferromagnetic spin, facilitating the use of such materials in antiferromagnetic spintronics and neuromorphic computing applications., Comment: Accepted in Physical Review Applied
- Published
- 2021
- Full Text
- View/download PDF
7. Fourfold Differential Photoelectron Circular Dichroism
- Author
-
Fehre, K., Novikovskiy, N. M., Grundmann, S., Kastirke, G., Eckart, S., Trinter, F., Rist, J., Hartung, A., Trabert, D., Janke, C., Nalin, G., Pitzer, M., Zeller, S., Wiegandt, F., Weller, M., Kircher, M., Hofmann, M., Schmidt, L. Ph. H., Knie, A., Hans, A., Ltaief, L. Ben, Ehresmann, A., Berger, R., Fukuzawa, H., Ueda, K., Schmidt-Böcking, H., Williams, J. B., Jahnke, T., Dörner, R., Schöffer, M. S., and Demekhin, Ph. V.
- Subjects
Physics - Atomic and Molecular Clusters - Abstract
We report on a joint experimental and theoretical study of photoelectron circular dichroism (PECD) in methyloxirane. By detecting O 1s-photoelectrons in coincidence with fragment ions, we deduce the molecule's orientation and photoelectron emission direction in the laboratory frame. Thereby, we retrieve a fourfold differential PECD clearly beyond 50%. This strong chiral asymmetry is reproduced by ab initio electronic structure calculations. Providing such a pronounced contrast makes PECD of fixed-in-space chiral molecules an even more sensitive tool for chiral recognition in the gas phase., Comment: 5 figures
- Published
- 2021
- Full Text
- View/download PDF
8. Photoelectron circular dichroism of O 1$s$-photoelectrons of uniaxially oriented trifluoromethyloxirane: Energy dependence and sensitivity to molecular configuration
- Author
-
Nalin, G., Fehre, K., Trinter, F., Novikovskiy, N. M., Anders, N., Trabert, D., Grundmann, S., Kircher, M., Khan, A., Tomar, R., Hofmann, M., Waitz, M., Vela-Perez, I., Fukuzawa, H., Ueda, K., Williams, J., Kargin, D., Maurer, M., Küstner-Wetekam, C., Marder, L., Viehmann, J., Knie, A., Jahnke, T., Ilchen, M., Dörner, R., Pietschnig, R., Demekhin, Ph. V., and Schöffler, M. S.
- Subjects
Physics - Chemical Physics ,Physics - Atomic and Molecular Clusters - Abstract
The photoelectron circular dichroism (PECD) of the O 1s-photoelectrons of trifluoromethyloxirane(TFMOx) is studied experimentally and theoretically for different photoelectron kinetic energies. The experiments were performed employing circularly polarized synchrotron radiation and coincidentelectron and fragment ion detection using Cold Target Recoil Ion Momentum Spectroscopy. The corresponding calculations were performed by means of the Single Center method within the relaxed-core Hartree-Fock approximation. We concentrate on the energy dependence of the differential PECD of uniaxially oriented TFMOx molecules, which is accessible through the employed coincident detection. We also compare results for differential PECD of TFMOx to those obtained for the equivalent fragmentation channel and similar photoelectron kinetic energy of methyloxirane (MOx), studied in our previous work. Thereby, we investigate the influence of the substitution of the methyl-group by the trifluoromethyl-group at the chiral center on the molecular chiral response. Finally, the presently obtained angular distribution parameters are compared to those available in literature., Comment: 6 figs
- Published
- 2021
- Full Text
- View/download PDF
9. Correlation Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule
- Author
-
Barillot, T., Alexander, O., Cooper, B., Driver, T., Garratt, D., Li, S., Haddad, A. Al, Sanchez-Gonzalez, A., Agåker, M., Arrell, C., Bearpark, M., Berrah, N., Bostedt, C., Bozek, J., Brahms, C., Bucksbaum, P. H., Clark, A., Doumy, G., Feifel, R., Frasinski, L. J., Jarosch, S., Johnson, A. S., Kjellsson, L., Kolorenč, P., Kumagai, Y., Larsen, E. W., Matia-Hernando, P., Robb, M., Rubensson, J. -E., Ruberti, M., Sathe, C., Squibb, R. J., Tan, A., Tisch, J. W. G., Vacher, M., Walke, D. J., Wolf, T. J. A., Wood, D., Zhaunerchyk, V., Walter, P., Osipov, T., Marinelli, A., Maxwell, T., Coffee, R., Lutman, A. A., Averbukh, V., Ueda, K., Cryan, J. P., and Marangos, J. P.
- Subjects
Physics - Chemical Physics ,Quantum Physics - Abstract
The possibility of suddenly ionized molecules undergoing extremely fast electron hole dynamics prior to significant structural change was first recognized more than 20 years ago and termed charge migration. The accurate probing of ultrafast electron hole dynamics requires measurements that have both sufficient temporal resolution and can detect the localization of a specific hole within the molecule. We report an investigation of the dynamics of inner valence hole states in isopropanol where we use an x-ray pump/x-ray probe experiment, with site and state-specific probing of a transient hole state localized near the oxygen atom in the molecule, together with an ab initio theoretical treatment. We record the signature of transient hole dynamics and make the first observation of dynamics driven by frustrated Auger-Meitner transitions. We verify that the hole lifetime is consistent with our theoretical prediction. This state-specific measurement paves the way to widespread application for observations of transient hole dynamics localized in space and time in molecules and thus to charge transfer phenomena that are fundamental in chemical and material physics.
- Published
- 2021
- Full Text
- View/download PDF
10. Resonant X-ray emission spectroscopy from broadband stochastic pulses at an X-ray free electron laser
- Author
-
Fuller, FD, Loukianov, A, Takanashi, T, You, D, Li, Y, Ueda, K, Fransson, T, Yabashi, M, Katayama, T, Weng, TC, Alonso-Mori, R, Bergmann, U, Jan Kern, Yachandra, VK, Wernet, P, and Yano, J
- Subjects
Bioengineering - Abstract
Hard X-ray spectroscopy is an element specific probe of electronic state, but signals are weak and require intense light to study low concentration samples. Free electron laser facilities offer the highest intensity X-rays of any available light source. The light produced at such facilities is stochastic, with spikey, broadband spectra that change drastically from shot to shot. Here, using aqueous ferrocyanide, we show that the resonant X-ray emission (RXES) spectrum can be inferred by correlating for each shot the fluorescence intensity from the sample with spectra of the fluctuating, self-amplified spontaneous emission (SASE) source. We obtain resolved narrow and chemically rich information in core-to-valence transitions of the pre-edge region at the Fe K-edge. Our approach avoids monochromatization, provides higher photon flux to the sample, and allows non-resonant signals like elastic scattering to be simultaneously recorded. The spectra obtained match well with spectra measured using a monochromator. We also show that inaccurate measurements of the stochastic light spectra reduce the measurement efficiency of our approach.
- Published
- 2021
11. A new route for enantio-sensitive structure determination by photoelectron scattering on molecules in the gas phase
- Author
-
Fehre, K., Novikovskiy, N. M., Grundmann, S., Kastirke, G., Eckart, S., Trinter, F., Rist, J., Hartung, A., Trabert, D., Janke, Ch., Pitzer, M., Zeller, S., Wiegandt, F., Weller, M., Kircher, M., Nalin, G., Hofmann, M., Schmidt, L. Ph. H., Knie, A., Hans, A., Ltaief, L. Ben, Ehresmann, A., Berger, R., Fukuzawa, H., Ueda, K., Schmidt-Böcking, H., Williams, J. B., Jahnke, T., Dörner, R., Demekhin, Ph. V., and Schöffler, M. S.
- Subjects
Physics - Chemical Physics ,Physics - Applied Physics - Abstract
X-ray as well as electron diffraction are powerful tools for structure determination of molecules. Studies on randomly oriented molecules in the gas-phase address cases in which molecular crystals cannot be generated or the interaction-free molecular structure is to be addressed. Such studies usually yield partial geometrical information, such as interatomic distances. Here, we present a complementary approach, which allows obtaining insight to the structure, handedness and even detailed geometrical features of molecules in the gas phase. Our approach combines Coulomb explosion imaging, the information that is encoded in the molecular frame diffraction pattern of core-shell photoelectrons and ab initio computations. Using a loop-like analysis scheme we are able to deduce specific molecular coordinates with sensitivity even to the handedness of chiral molecules and the positions of individual atoms, as, e.g., protons., Comment: 13 pages, 3 figures
- Published
- 2021
- Full Text
- View/download PDF
12. Nonmagnetic-magnetic transition and magnetically ordered structure in SmS
- Author
-
Yoshida, S., Koyama, T., Yamada, H., Nakai, Y., Ueda, K., Mito, T., Kitagawa, K., and Haga, Y.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
SmS, a prototypical intermediate valence compound, has been studied by performing high-pressure nuclear magnetic resonance measurements on a $^{33}$S-enriched sample. The observation of an additional signal below 15-20 K above a nonmagnetic-magnetic transition pressure $P_{\rm c2} \approx 2$ GPa gives evidence of a magnetic transition. The absence of a Curie-term in the Knight shift near $P_{\rm c2}$ indicates that the localized character of $4f$ electrons is entirely screened and the mechanism of the magnetic ordering is not described within a simple localized model. Simultaneously, the line shape in the magnetically ordered state is incompatible with a spin density wave order. These suggest that the magnetic order in SmS may require an understanding beyond the conventional framework for heavy fermions. The fact that hyperfine fields from the ordered moments cancel out at the S site leads us to a conclusion that the ordered phase has a type II antiferromagnetic structure.
- Published
- 2020
- Full Text
- View/download PDF
13. Time-resolved study of resonant interatomic Coulombic decay in helium nanodroplets
- Author
-
LaForge, A. C., Michiels, R., Ovcharenko, Y., Ngai, A., Escartin, J. M., Berrah, N., Callegari, C., Clark, A., Coreno, M., Cucini, R., Di Fraia, M., Drabbels, M., Fasshauer, E., Finetti, P., Giannessi, L., Grazioli, C., Iablonskyi, D., Langbehn, B., Nishiyama, T., Oliver, V., Piseri, P., Plekan, O., Prince, K. C., Rupp, D., Stranges, S., Ueda, K., Sisourat, N., Eloranta, J., Pi, M., Barranco, M., Stienkemeier, F., Moeller, T., and Mudrich, M.
- Subjects
Physics - Atomic and Molecular Clusters - Abstract
When weakly-bound complexes are multiply excited by intense electromagnetic radiation, energy can be exchanged between neighboring atoms through a type of resonant interatomic Coulombic decay (ICD). This decay mechanism due to multiple excitations has been predicted to be relatively slow, typically lasting tens to hundreds of picoseconds. Here, we directly measure the ICD timescale in resonantly excited helium droplets using a high resolution, tunable, extreme ultraviolet free electron laser. Over an extensive range of droplet sizes and laser intensities, we discover the decay to be surprisingly fast, with decay times as fast as 400 femtoseconds, and to only present a weak dependence on the density of the excited states. Using a combination of time dependent density functional theory and ab initio quantum chemistry calculations, we elucidate the mechanisms of this ultrafast decay process where pairs of excited helium atoms in one droplet strongly attract each other and form merging void bubbles which drastically accelerates ICD.
- Published
- 2020
- Full Text
- View/download PDF
14. Proximate ferromagnetic state in the Kitaev model material $\alpha$-RuCl$_{3}$
- Author
-
Suzuki, H., Liu, H., Bertinshaw, J., Ueda, K., Kim, H., Laha, S., Weber, D., Yang, Z., Wang, L., Takahashi, H., Fürsich, K., Minola, M., Lotsch, B. V., Kim, B. J., Yavaş, H., Daghofer, M., Chaloupka, J., Khaliullin, G., Gretarsson, H., and Keimer, B.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
$\alpha$-RuCl$_{3}$ is a major candidate for the realization of the Kitaev quantum spin liquid, but its zigzag antiferromagnetic order at low temperatures indicates deviations from the Kitaev model. We have quantified the spin Hamiltonian of $\alpha$-RuCl$_{3}$ by a resonant inelastic x-ray scattering study at the Ru $L_{3}$ absorption edge. In the paramagnetic state, the quasi-elastic intensity of magnetic excitations has a broad maximum around the zone center without any local maxima at the zigzag magnetic Bragg wavevectors. This finding implies that the zigzag order is fragile and readily destabilized by competing ferromagnetic correlations. The classical ground state of the experimentally determined Hamiltonian is actually ferromagnetic. The zigzag state is stabilized via a quantum "order by disorder" mechanism, leaving ferromagnetism -- along with the Kitaev spin liquid -- as energetically proximate metastable states. The three closely competing states and their collective excitations hold the key to the theoretical understanding of the unusual properties of $\alpha$-RuCl$_{3}$ in magnetic fields.
- Published
- 2020
- Full Text
- View/download PDF
15. Spin-wave gap collapse in Rh-doped Sr2IrO4
- Author
-
Bertinshaw, J., Kim, J. K., Porras, J., Ueda, K., Sung, N. H., Efimenko, A., Bombardi, A., Kim, Jungho, Keimer, B., and Kim, B. J.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
We use resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge to study the effect of hole doping upon the Jeff=1/2 Mott-insulating state in Sr2IrO4, via Rh replacement of the Ir site. The spin-wave gap, associated with XY-type spin-exchange anisotropy, collapses with increasing Rh content, prior to the suppression of the Mott-insulating state and in contrast to electron doping via La substitution of the Sr site. At the same time, despite heavy damping, the d-d excitation spectra retain their overall amplitude and dispersion character. A careful study of the spin-wave spectrum reveals that deviations from the J1-J2-J3 Heisenberg used to model the pristine system disappear at intermediate doping levels. These findings are interpreted in terms of a modulation of Ir-Ir correlations due to the influence of Rh impurities upon nearby Ir wave functions, even as the single-band Jeff=1/2 model remains valid up to full carrier delocalization. They underline the importance of the transition metal site symmetry when doping pseudospin systems such as Sr2IrO4., Comment: 5 pages, 3 figures
- Published
- 2020
- Full Text
- View/download PDF
16. Observation of spin-orbit excitations and Hund's multiplets in Ca$_2$RuO$_4$
- Author
-
Gretarsson, H., Suzuki, H., Kim, Hoon, Ueda, K., Krautloher, M., Kim, B. J., Yavaş, H., Khaliullin, G., and Keimer, B.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
We use Ru $L_3$-edge (2838.5 eV) resonant inelastic x-ray scattering (RIXS) to quantify the electronic structure of Ca$_2$RuO$_4$, a layered $4d$-electron compound that exhibits a correlation-driven metal-insulator transition and unconventional antiferromagnetism. We observe a series of Ru intra-ionic transitions whose energies and intensities are well described by model calculations. In particular, we find a $\rm{J}=0\rightarrow 2$ spin-orbit excitation at 320 meV, as well as Hund's-rule driven $\rm{S}=1\rightarrow 0$ spin-state transitions at 750 and 1000 meV. The energy of these three features uniquely determines the spin-orbit coupling, tetragonal crystal-field energy, and Hund's rule interaction. The parameters inferred from the RIXS spectra are in excellent agreement with the picture of excitonic magnetism that has been devised to explain the collective modes of the antiferromagnetic state. $L_3$-edge RIXS of Ru compounds and other $4d$-electron materials thus enables direct measurements of interactions parameters that are essential for realistic model calculations., Comment: 9 pages and 4 figures. accepted in PRB
- Published
- 2019
- Full Text
- View/download PDF
17. Pressure induced evolution of band structure in black phosphorus studied by $^{31}$P-NMR
- Author
-
Fujii, T., Nakai, Y., Akahama, Y., Ueda, K., and Mito, T.
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
Two-dimensional layered semiconductor black phosphorus (BP), a promising pressure induced Dirac system as predicted by band structure calculations, has been studied by $^{31}$P-nuclear magnetic resonance. Band calculations have been also carried out to estimate the density of states $D(E)$. The temperature and pressure dependences of nuclear spin lattice relaxation rate $1/T_1$ in the semiconducting phase are well reproduced using the derived $D(E)$, and the resultant pressure dependence of semiconducting gap is in good accordance with previous reports, giving a good confirmation that the band calculation on BP is fairly reliable. The present analysis of $1/T_1$ data with the complemental theoretical calculations allows us to extract essential information, such as the pressure dependences of $D(E)$ and chemical potential, as well as to decompose observed $1/T_1$ into intrinsic and extrinsic contributions. An abrupt increase in $1/T_1$ at 1.63GPa indicates that the semiconducting gap closes, resulting in an enhancement of conductivity., Comment: 11 pages, 4 figures
- Published
- 2019
- Full Text
- View/download PDF
18. Spin waves and spin-state transitions in a ruthenate high-temperature antiferromagnet
- Author
-
Suzuki, H., Gretarsson, H., Ishikawa, H., Ueda, K., Yang, Z., Liu, H., Kim, H., Kukusta, D., Yaresko, A., Minola, M., Sears, J. A., Francoual, S., Wille, H. -C., Nuss, J., Takagi, H., Kim, B. J., Khaliullin, G., Yavas, H., and Keimer, B.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
Ruthenium compounds play prominent roles in materials research ranging from oxide electronics to catalysis, and serve as a platform for fundamental concepts such as spin-triplet superconductivity, Kitaev spin-liquids, and solid-state analogues of the Higgs mode in particle physics. However, basic questions about the electronic structure of ruthenates remain unanswered, because several key parameters (including the Hund's-rule, spin-orbit, and exchange interactions) are comparable in magnitude, and their interplay is poorly understood - partly due to difficulties in synthesizing sizable single crystals for spectroscopic experiments. Here we introduce a resonant inelastic x-ray scattering (RIXS) technique capable of probing collective modes in microcrystals of $4d$-electron materials. We present a comprehensive set of data on spin waves and spin-state transitions in the honeycomb antiferromagnet SrRu$_{2}$O$_{6}$, which possesses an unusually high N\'eel temperature. The new RIXS method provides fresh insight into the unconventional magnetism of SrRu$_{2}$O$_{6}$, and enables momentum-resolved spectroscopy of a large class of $4d$ transition-metal compounds., Comment: The original submitted version of the published manuscript. https://www.nature.com/articles/s41563-019-0327-2
- Published
- 2019
- Full Text
- View/download PDF
19. Two-photon resonant excitation of interatomic coulombic decay in neon dimers
- Author
-
Dubrouil, A, Reduzzi, M, Devetta, M, Feng, C, Hummert, J, Finetti, P, Plekan, O, Grazioli, C, Di Fraia, M, Lyamayev, V, La Forge, A, Katzy, R, Stienkemeier, F, Ovcharenko, Y, Coreno, M, Berrah, N, Motomura, K, Mondal, S, Ueda, K, Prince, K C, Callegari, C, Kuleff, A I, Demekhin, Ph V, and Sansone, G
- Subjects
Physics - Atomic Physics ,Physics - Optics - Abstract
The recent availability of intense and ultrashort extreme ultraviolet sources opens the possibility to investigate ultrafast electronic relaxation processes in matter in an unprecedented regime. In this work we report on the observation of two-photon excitation of interatomic Coulombic decay (ICD) in neon dimers using the tunable intense pulses delivered by the free electron laser FERMI@Elettra. The unique characteristics of FERMI (narrow bandwidth, spectral stability, and tunability) allow one to resonantly excite specific ionization pathways and to observe a clear signature of the ICD mechanism in the ratio of the ion yield created by Coulomb explosion. The present experimental results are explained by \emph{ab initio} electronic structure and nuclear dynamics calculations.
- Published
- 2019
20. Time-resolved observation of interatomic Coulombic decay induced by two-photon double excitation of Ne$_{2}$
- Author
-
Takanashi, T., Golubev, N. V., Callegari, C., Fukuzawa, H., Motomura, K., Iablonskyi, D., Kumagai, Y., Mondal, S., Tachibana, T., Nagaya, K., Nishiyama, T., Matsunami, K., Johnsson, P., Piseri, P., Sansone, G., Dubrouil, A., Reduzzi, M., Carpeggiani, P., Vozzi, C., Devetta, M., Negro, M., Faccialà, D., Calegari, F., Trabattoni, A., Castrovilli, M. C., Ovcharenko, Y., Mudrich, M., Stienkemeier, F., Coreno, M., Alagia, M., Schütte, B., Berrah, N., Plekan, O., Finetti, P., Spezzani, C., Ferrari, E., Allaria, E., Penco, G., Serpico, C., De Ninno, G., Diviacco, B., Di Mitri, S., Giannessi, L., Jabbari, G., Prince, K. C., Cederbaum, L. S., Demekhin, Ph. V., Kuleff, A. I., and Ueda, K.
- Subjects
Physics - Atomic Physics ,Physics - Atomic and Molecular Clusters ,Physics - Optics - Abstract
The hitherto unexplored two-photon doubly-excited states [Ne$^{*}$($2p^{-1}3s$)]$_{2}$ were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD) which predominantly produces singly-ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne$_{2}^{+}$ ions was recorded as a function of delay between the XUV pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly-excited states, 390 (-130 / +450} fs, and of the short-lived ones, less than 150~fs, are in good agreement with \emph{ab initio} quantum mechanical calculations.
- Published
- 2019
21. Evidence for gradual evolution of low-energy fluctuations underlying the first-order structural and valence order in YbPd
- Author
-
Nakanishi, R., Fujii, T., Nakai, Y., Ueda, K., Hirata, M., Oyama, K., Mitsuda, A., Wada, H., and Mito, T.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
The valence orders at $T_a=125$ K and $T_b=105$ K in the cubic compound YbPd have been investigated by $^{105}$Pd-nuclear magnetic resonance (NMR) measurements. Significant decrease in the density of states at the Fermi energy below $T_a$ is evident from the measurement of nuclear spin lattice relaxation rate $1/T_1$, suggesting that the instabilities of Fermi surface are associated with the transitions. Moreover we observed the unusual evolution of low-energy fluctuations toward the valence transition at $T_a$ behind its drastic first-order nature. The structural transition accompanying the valence order may occur as a result of cooperative effect of Fermi surface and valence instabilities., Comment: 5 pages, 3 figures
- Published
- 2019
22. Autoionization dynamics of He nanodroplets resonantly excited by intense XUV laser pulses
- Author
-
Ovcharenko, Y., LaForge, A., Langbehn, B., Plekan, O., Cucini, R., Finetti, P., O'Keeffe, P., Iablonskyi, D., Nishiyama, T., Ueda, K., Piseri, P., DiFraia, M., Richter, R., Coreno, M., Callegari, C., Prince, K. C., Stienkemeier, F., Moller, T., and Mudrich, M.
- Subjects
Physics - Atomic and Molecular Clusters ,14J60 (Primary) 14F05, 14J26 (Secondary) - Abstract
The ionization dynamics of helium droplets in a wide size range from 220 to 10^6 He atoms irradiated with intense femtosecond extreme ultraviolet (XUV) pulses of 10^9 {\div} 10^{12} W/cm2 power density is investigated in detail by photoelectron spectroscopy. Helium droplets are resonantly excited in the photon energy range from ~ 21 eV (corresponding to the atomic 1s2s state) up to the atomic ionization potential (IP) at ~ 25 eV. A complex evolution of the electron spectra as a function of droplet size and XUV intensity is observed, ranging from atomic-like narrow peaks due to binary autoionization, to an unstructured feature characteristic of electron emission from a nanoplasma. The experimental results are analyzed and interpreted with the help of numerical simulations based on rate equations taking into account various processes such as multi-step ionization, interatomic Coulombic decay (ICD), secondary inelastic collisions, desorption of electronically excited atoms, collective autoionization (CAI) and further relaxation processes., Comment: 20 pages, 14 figures, 43 references
- Published
- 2019
23. Dirac semimetal like transport features in high-quality Bi0.96Sb0.04 thin films
- Author
-
Hadate, Y., Asano, H., and Ueda, K.
- Published
- 2023
- Full Text
- View/download PDF
24. Photoelectron Diffraction Imaging of a Molecular Breakup Using an X-Ray Free-Electron Laser
- Author
-
Kastirke, G, Schöffler, MS, Weller, M, Rist, J, Boll, R, Anders, N, Baumann, TM, Eckart, S, Erk, B, De Fanis, A, Fehre, K, Gatton, A, Grundmann, S, Grychtol, P, Hartung, A, Hofmann, M, Ilchen, M, Janke, C, Kircher, M, Kunitski, M, Li, X, Mazza, T, Melzer, N, Montano, J, Music, V, Nalin, G, Ovcharenko, Y, Pier, A, Rennhack, N, Rivas, DE, Dörner, R, Rolles, D, Rudenko, A, Schmidt, P, Siebert, J, Strenger, N, Trabert, D, Vela-Perez, I, Wagner, R, Weber, T, Williams, JB, Ziolkowski, P, Schmidt, LPH, Czasch, A, Trinter, F, Meyer, M, Ueda, K, Demekhin, PV, and Jahnke, T
- Subjects
Astronomical and Space Sciences ,Condensed Matter Physics ,Quantum Physics - Abstract
A central motivation for the development of x-ray free-electron lasers has been the prospect of time-resolved single-molecule imaging with atomic resolution. Here, we show that x-ray photoelectron diffraction - where a photoelectron emitted after x-ray absorption illuminates the molecular structure from within - can be used to image the increase of the internuclear distance during the x-ray-induced fragmentation of an O2 molecule. By measuring the molecular-frame photoelectron emission patterns for a two-photon sequential K-shell ionization in coincidence with the fragment ions, and by sorting the data as a function of the measured kinetic energy release, we can resolve the elongation of the molecular bond by approximately 1.2 a.u. within the duration of the x-ray pulse. The experiment paves the road toward time-resolved pump-probe photoelectron diffraction imaging at high-repetition-rate x-ray free-electron lasers.
- Published
- 2020
25. Spin-orbit-controlled metal–insulator transition in Sr2IrO4
- Author
-
Zwartsenberg, B, Day, RP, Razzoli, E, Michiardi, M, Xu, N, Shi, M, Denlinger, JD, Cao, G, Calder, S, Ueda, K, Bertinshaw, J, Takagi, H, Kim, BJ, Elfimov, IS, and Damascelli, A
- Subjects
cond-mat.str-el ,Mathematical Sciences ,Physical Sciences ,Fluids & Plasmas - Abstract
In the context of correlated insulators, where electron–electron interactions (U) drive the localization of charge carriers, the metal–insulator transition is described as either bandwidth- or filling-controlled1. Motivated by the challenge of the insulating phase in Sr2IrO4, a new class of correlated insulators has been proposed, in which spin–orbit coupling (SOC) is believed to renormalize the bandwidth of the half-filled jeff = 1/2 doublet, allowing a modest U to induce a charge-localized phase2,3. Although this framework has been tacitly assumed, a thorough characterization of the ground state has been elusive4,5. Furthermore, direct evidence for the role of SOC in stabilizing the insulating state has not been established, because previous attempts at revealing the role of SOC6,7 have been hindered by concurrently occurring changes to the filling8–10. We overcome this challenge by employing multiple substituents that introduce well-defined changes to the signatures of SOC and carrier concentration in the electronic structure, as well as a new methodology that allows us to monitor SOC directly. Specifically, we study Sr2Ir1−xTxO4 (T = Ru, Rh) by angle-resolved photoemission spectroscopy, combined with ab initio and supercell tight-binding calculations. This allows us to distinguish relativistic and filling effects, thereby establishing conclusively the central role of SOC in stabilizing the insulating state of Sr2IrO4. Most importantly, we estimate the critical value for SOC in this system to be λc = 0.42 ± 0.01 eV, and provide the first demonstration of a spin–orbit-controlled metal–insulator transition.
- Published
- 2020
26. Rescattering photoelectron spectroscopy of CO2 molecule with an analytical returning electron wavepacket
- Author
-
Okunishi, M, Ito, Y, Sharma, V, Aktar, S, Morishita, T, Dnestryan, AI, Tolstikhin, OI, Lucchese, RR, and Ueda, K
- Subjects
Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Condensed Matter Physics ,Other Physical Sciences - Abstract
Angle-resolved photoelectron momentum distributions of rescattering electron generated by intense infrared laser pulses were measured for CO2 molecules. It is shown that the measured distributions along the out-ermost backward rescattering caustic are well reproduced by calculations based on a newly developed factorization formula with the analytical returning photoelectron wave packet.
- Published
- 2020
27. Validation of Numerical Predictions of Lateral Spreading Based on Hollow-Cylinder Torsional Shear Tests and a Large Centrifuge-Models Database
- Author
-
Vargas, R., Tang, Z., Ueda, K., Uzuoka, R., Ansal, Atilla, Series Editor, Bommer, Julian, Editorial Board Member, Bray, Jonathan D., Editorial Board Member, Pitilakis, Kyriazis, Editorial Board Member, Yasuda, Susumu, Editorial Board Member, Wang, Lanmin, editor, Zhang, Jian-Min, editor, and Wang, Rui, editor
- Published
- 2022
- Full Text
- View/download PDF
28. Rescattering photoelectron spectroscopy of the CO2 molecule: Progress towards experimental discrimination between theoretical target-structure models
- Author
-
Okunishi, M, Ito, Y, Sharma, V, Aktar, S, Ueda, K, Lucchese, RR, Dnestryan, AI, Tolstikhin, OI, Inoue, S, Matsui, H, and Morishita, T
- Abstract
Photoelectron momentum distributions (PEMDs) generated in strong-field ionization of randomly oriented CO2 molecules by intense infrared laser pulses at 1300-, 1450-, and 1650-nm wavelengths are measured experimentally and analyzed theoretically. The experimental PEMDs extracted along the outermost backward rescattering caustic are well reproduced by theoretical calculations based on the recently derived factorization formula with an analytical returning photoelectron wave packet (RWP). The sensitivity of the theoretical results to the target structure models used in the calculations is investigated. It is shown that RWPs obtained in the single-active-electron (SAE) approximation and by the Hartree-Fock method have only minor differences. On the other hand, differential cross sections (DCSs) for elastic scattering of a photoelectron on the parent molecular ion calculated by ab initio, SAE, and independent-atom model methods are considerably different. This difference almost disappears after averaging over molecular orientations, so the present experiment does not enable us to discriminate between the different target structure models. However, we show that such a discrimination should become possible by measuring PEMD with aligned molecules. This will provide an access to the rich target structure information contained in the DCS.
- Published
- 2019
29. Combining Multiple Indices of Diffusion Tensor Imaging Can Better Differentiate Patients with Traumatic Brain Injury from Healthy Subjects
- Author
-
Abdelrahman HAF, Ubukata S, Ueda K, Fujimoto G, Oishi N, Aso T, and Murai T
- Subjects
diffuse axonal injury ,diffusion tensor imaging ,machine learning ,screening ,traumatic brain injury ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 ,Neurology. Diseases of the nervous system ,RC346-429 - Abstract
Hiba Abuelgasim Fadlelmoula Abdelrahman,1 Shiho Ubukata,2 Keita Ueda,1 Gaku Fujimoto,1 Naoya Oishi,2 Toshihiko Aso,3 Toshiya Murai1 1Kyoto University Graduate School of Medicine-Department of Psychiatry, Kyoto, 606-8507, Japan; 2Kyoto University Graduate School of Medicine-Medical Innovation Center, Kyoto, 606-8507, Japan; 3Laboratory for Brain Connectomics Imaging, RIKEN Center for Biosystems Dynamics Research, Kobe, 650-0047, JapanCorrespondence: Hiba Abuelgasim Fadlelmoula Abdelrahman, Email hiba.abulgasim@gmail.comAim: Diffuse axonal injury (DAI) is one of the most common pathological features of traumatic brain injury (TBI). Diffusion tensor imaging (DTI) indices can be used to identify and quantify white matter microstructural changes following DAI. Recently, many studies have used DTI with various machine learning approaches to predict white matter microstructural changes following TBI. The current study sought to examine whether our classification approach using multiple DTI indices in conjunction with machine learning is a useful tool for diagnosing/classifying TBI patients and healthy controls.Methods: Participants were adult patients with chronic TBI (n = 26) with DAI pathology, and age- and sex-matched healthy controls (n = 26). DTI images were obtained from all participants. Tract-based spatial statistics analyses were applied to DTI images. Classification models were built using principal component analysis and support vector machines. Receiver operator characteristic curve analysis and area under the curve were used to assess the classification performance of the different classifiers.Results: Tract-based spatial statistics revealed significantly decreased fractional anisotropy, as well as increased mean diffusivity, axial diffusivity, and radial diffusivity in patients with TBI compared with healthy controls (all p-values < 0.01). The principal component analysis and support vector machine-based machine learning classification using combined DTI indices classified patients with TBI and healthy controls with an accuracy of 90.5% with an area under the curve of 93 ± 0.09.Conclusion: These results highlight the potential of our approach combining multiple DTI measures to identify patients with TBI.Keywords: diffuse axonal injury, diffusion tensor imaging, machine learning, screening, traumatic brain injury
- Published
- 2022
30. Quantum phase transition of an organic spin liquid tuned by mixing counterions
- Author
-
Ueda, K., primary, Fujiyama, S., additional, and Kato, R., additional
- Published
- 2024
- Full Text
- View/download PDF
31. Roadmap on photonic, electronic and atomic collision physics: I. Light-matter interaction
- Author
-
Ueda, K, Sokell, E, Schippers, S, Aumayr, F, Sadeghpour, H, Burgdörfer, J, Lemell, C, Tong, XM, Pfeifer, T, Calegari, F, Palacios, A, Martin, F, Corkum, P, Sansone, G, Gryzlova, EV, Grum-Grzhimailo, AN, Piancastelli, MN, Weber, PM, Steinle, T, Amini, K, Biegert, J, Berrah, N, Kukk, E, Santra, R, Müller, A, Dowek, D, Lucchese, RR, McCurdy, CW, Bolognesi, P, Avaldi, L, Jahnke, T, Schöffler, MS, Dörner, R, Mairesse, Y, Nahon, L, Smirnova, O, Schlathölter, T, Campbell, EEB, Rost, JM, Meyer, M, and Tanaka, KA
- Subjects
light-matter interaction ,new light sources ,synchrotron radiation sources ,femtosecond lasers ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Optical Physics ,Theoretical and Computational Chemistry ,General Physics ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics - Abstract
We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field.
- Published
- 2019
32. Operando study of Pd(100) surface during CO oxidation using ambient pressure x-ray photoemission spectroscopy
- Author
-
Yu, Y, Kim, D, Lim, H, Kim, G, Koh, YE, Ueda, K, Hiwasa, S, Mase, K, Bournel, F, Gallet, JJ, Rochet, F, Crumlin, EJ, Ross, PN, Kondoh, H, Noh, DY, and Mun, BS
- Subjects
Optical Physics ,Quantum Physics ,Electrical and Electronic Engineering - Abstract
The surface chemical states of Pd(100) during CO oxidation were investigated using ambient pressure x-ray photoelectron spectroscopy and mass spectroscopy. Under the reactant ratio of CO/O 2 = 0.1, i.e. an oxygen-rich reaction condition, the formation of surface oxides was observed with the onset of CO oxidation reaction at T = 525 K. As the reactant ratio (CO/O 2 ) increased from 0.1 to 1.0, ∼ 90 % surface oxides remains on surface during the reaction. Upon the formation of surface oxides, the core level shift of oxygen gas phase peak was observed, indicating that change of surface work function. As CO oxidation takes places, i.e. making a transition from CO covered surface to the oxidic surface, the work functions of surface oxide on Pd(100) and Pt(110) display opposite behavior.
- Published
- 2019
33. Study on Compression Fatigue of Rubber Bearings Used in Low Temperature Environment
- Author
-
Sato, T., Imai, T., Kuji, S., Ueda, K., Nishi, H., di Prisco, Marco, Series Editor, Chen, Sheng-Hong, Series Editor, Vayas, Ioannis, Series Editor, Kumar Shukla, Sanjay, Series Editor, Sharma, Anuj, Series Editor, Kumar, Nagesh, Series Editor, Wang, Chien Ming, Series Editor, Dao, Vinh, editor, and Kitipornchai, Sritawat, editor
- Published
- 2021
- Full Text
- View/download PDF
34. Observation and Control of Laser-Enabled Auger Decay
- Author
-
Iablonskyi, D., Ueda, K., Ishikawa, Kenichi L., Kheifets, A. S., Carpeggiani, P., Reduzzi, M., Ahmadi, H., Comby, A., Sansone, G., Csizmadia, T., Kuehn, S., Ovcharenko, E., Mazza, T., Meyer, M., Fischer, A., Callegari, C., Plekan, O., Finetti, P., Allaria, E., Ferrari, E., Roussel, E., Gauthier, D., Giannessi, L., and Prince, K. C.
- Subjects
Physics - Atomic Physics - Abstract
Single photon laser enabled Auger decay (spLEAD) has been redicted theoretically [Phys. Rev. Lett. 111, 083004 (2013)] and here we report its first experimental observation in neon. Using coherent, bichromatic free-electron laser pulses, we have detected the process and coherently controlled the angular distribution of the emitted electrons by varying the phase difference between the two laser fields. Since spLEAD is highly sensitive to electron correlation, this is a promising method for probing both correlation and ultrafast hole migration in more complex systems., Comment: 5 pages, 3 figures
- Published
- 2017
- Full Text
- View/download PDF
35. Coherent control with a short-wavelength Free Electron Laser
- Author
-
Prince, K. C., Allaria, E., Callegari, C., Cucini, R., De Ninno, G., Di Mitri, S., Diviacco, B., Ferrari, E., Finetti, P., Gauthier, D., Giannessi, L., Mahne, N., Penco, G., Plekan, O., Raimondi, L., Rebernik, P., Roussel, E., Svetina, C., Trovò, M., Zangrando, M., Negro, M., Carpeggiani, P., Reduzzi, M., Sansone, G., Grum-Grzhimailo, A. N., Gryzlova, E. V., Strakhova, S. I., Bartschat, K., Douguet, N., Venzke, J., Iablonskyi, D., Kumagai, Y., Takanashi, T., Ueda, K., Fischer, A., Coreno, M., Stienkemeier, F., Ovcharenko, Y., Mazza, T., and Meyer, M.
- Subjects
Physics - Optics - Abstract
XUV and X-ray Free Electron Lasers (FELs) produce short wavelength pulses with high intensity, ultrashort duration, well-defined polarization and transverse coherence, and have been utilised for many experiments previously possible at long wavelengths only: multiphoton ionization, pumping an atomic laser, and four-wave mixing spectroscopy. However one important optical technique, coherent control, has not yet been demonstrated, because Self- Amplified Spontaneous Emission FELs have limited longitudinal coherence. Single-colour pulses from the FERMI seeded FEL are longitudinally coherent, and two-colour emission is predicted to be coherent. Here we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and the asymmetry of the photoelectron angular distribution was controlled by adjusting the phase, with temporal resolution 3 attoseconds. This opens the door to new shortwavelength coherent control experiments with ultrahigh time resolution and chemical sensitivity.
- Published
- 2017
- Full Text
- View/download PDF
36. Diamond/graphene (carbon sp3-sp2) heterojunctions for neuromorphic device applications.
- Author
-
Iwane, H., Saito, G., Muto, S., and Ueda, K.
- Published
- 2024
- Full Text
- View/download PDF
37. Existence probabilities of single Si atoms diffusing in Si(111)-(7 × 7) half-unit cells at room temperature.
- Author
-
Ueda, K., Diao, Z., Hou, L., Yamashita, H., and Abe, M.
- Subjects
- *
SCANNING tunneling microscopy , *ATOMS , *SURFACE cleaning , *IMAGE processing - Abstract
We determined the probabilities of finding diffusing Si atoms in faulted and unfaulted half-unit cells on the Si(111)-(7 × 7) surface. An adsorbed Si atom on the surface at room temperature moved in the half-unit cells. The atom was adsorbed via atom manipulation and located via under-sampled scanning tunneling microscopy. Images of the half-unit cells with the diffusing Si atom and images of the clean surface were superimposed via image processing to calculate differences used to determine the Si atom positions at room temperature. There were different probabilities for Si atom diffusion in faulted and unfaulted half-unit cells. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
38. Machine learning applied to single-shot x-ray diagnostics in an XFEL
- Author
-
Sanchez-Gonzalez, A., Micaelli, P., Olivier, C., Barillot, T. R., Ilchen, M., Lutman, A. A., Marinelli, A., Maxwell, T., Achner, A., Agåker, M., Berrah, N., Bostedt, C., Buck, J., Bucksbaum, P. H., Montero, S. Carron, Cooper, B., Cryan, J. P., Dong, M., Feifel, R., Frasinski, L. J., Fukuzawa, H., Galler, A., Hartmann, G., Hartmann, N., Helml, W., Johnson, A. S., Knie, A., Lindahl, A. O., Liu, J., Motomura, K., Mucke, M., O'Grady, C., Rubensson, J-E., Simpson, E. R., Squibb, R. J., Såthe, C., Ueda, K., Vacher, M., Walke, D. J., Zhaunerchyk, V., Coffee, R. N., and Marangos, J. P.
- Subjects
Physics - Data Analysis, Statistics and Probability ,Physics - Accelerator Physics ,Statistics - Machine Learning - Abstract
X-ray free-electron lasers (XFELs) are the only sources currently able to produce bright few-fs pulses with tunable photon energies from 100 eV to more than 10 keV. Due to the stochastic SASE operating principles and other technical issues the output pulses are subject to large fluctuations, making it necessary to characterize the x-ray pulses on every shot for data sorting purposes. We present a technique that applies machine learning tools to predict x-ray pulse properties using simple electron beam and x-ray parameters as input. Using this technique at the Linac Coherent Light Source (LCLS), we report mean errors below 0.3 eV for the prediction of the photon energy at 530 eV and below 1.6 fs for the prediction of the delay between two x-ray pulses. We also demonstrate spectral shape prediction with a mean agreement of 97%. This approach could potentially be used at the next generation of high-repetition-rate XFELs to provide accurate knowledge of complex x-ray pulses at the full repetition rate., Comment: 12 pages, 8 figures
- Published
- 2016
- Full Text
- View/download PDF
39. Changes in site-specific shape resonances in nitrogen K-shell photoionization of N2O induced by vibrational excitation
- Author
-
Hoshino, M, Kato, H, Kuze, N, Tanaka, H, Fukuzawa, H, Ueda, K, and Lucchese, RR
- Subjects
x-ray photoelectron spectroscopy ,inner-shell ionization cross sections ,asymmetry parameters ,vibrationally excited N2O molecule ,hot molecules ,Optics - Abstract
The central (Nc) and terminal (Nt) nitrogen K-shell photoelectron spectra (PESs) of N2O molecules have been measured in the σ shape resonance energy region at temperatures of ∼300 and ∼630 K. Estimating vibrational populations based on the Boltzmann distribution at these temperatures, PESs of vibrationally ground and bending-excited levels in the initial electronic ground state were extracted. Vibrationally integrated partial cross sections and asymmetry parameters for ionization from vibrationally ground and bending-excited levels were obtained as a function of the incident photon energy by integrating PESs over the vibrational levels of the core-hole states. In Nc photoionization, the shape resonance from the bending-excited level was found to be shifted to the lower photon energy side and to become narrower than that from the ground vibrational level. In Nt photoionization from the bending-excited level, the downward shift of the resonance is more significant than that in Nc ionization. These experimental findings are qualitatively consistent with theoretical predictions and suggest that the shape resonance associated with the Nt core hole is more sensitive to the bending angle of the initial state than is the shape resonance associated with the Nc core hole. The asymmetry parameters for photoionization from the bending-excited level, however, showed almost the same behavior as those from the ground vibrational level for both K-shell photoionization channels and in the photon energy range studied here.
- Published
- 2018
40. Roadmap of ultrafast x-ray atomic and molecular physics
- Author
-
Young, L, Ueda, K, Gühr, M, Bucksbaum, PH, Simon, M, Mukamel, S, Rohringer, N, Prince, KC, Masciovecchio, C, Meyer, M, Rudenko, A, Rolles, D, Bostedt, C, Fuchs, M, Reis, DA, Santra, R, Kapteyn, H, Murnane, M, Ibrahim, H, Légaré, F, Vrakking, M, Isinger, M, Kroon, D, Gisselbrecht, M, L'Huillier, A, Wörner, HJ, and Leone, SR
- Subjects
ultrafast molecular dynamics ,x-ray spectroscopies and phenomena ,table-top sources ,x-ray free-electron lasers ,attosecond phenomena ,General Physics ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Optical Physics ,Theoretical and Computational Chemistry ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics - Abstract
X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (1020 W cm-2) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.
- Published
- 2018
41. Extraction of geometrical structure of ethylene molecules by laser-induced electron diffraction combined with ab initio scattering calculations
- Author
-
Ito, Y, Carranza, R, Okunishi, M, Lucchese, RR, and Ueda, K
- Abstract
We measured angle-resolved high-energy electron spectra emitted from C2H4 in an intense laser field, extracted field-free electron-ion elastic scattering differential cross sections (DCSs) according to quantitative rescattering theory, and obtained molecular contrast factors (MCFs) subtracting the incoherent sum of DCSs of all the atoms in the molecule. Comparing the results with ab initio scattering calculations and employing least-squares fitting, we have extracted the C-C and C-H bond lengths of the molecule with ∼5% uncertainty. This approach opens the way to retrieve the structure of hydrocarbon molecules, potentially at high temporal resolution, employing low collision energies where electron scattering is sensitive to the hydrogen atoms; and where the independent atom model calculations may fail to reproduce the experimentally extracted MCF.
- Published
- 2017
42. Validation of Numerical Predictions of Lateral Spreading Based on Hollow-Cylinder Torsional Shear Tests and a Large Centrifuge-Models Database
- Author
-
Vargas, R., primary, Tang, Z., additional, Ueda, K., additional, and Uzuoka, R., additional
- Published
- 2022
- Full Text
- View/download PDF
43. Tracing Photoinduced Hydrogen Migration in Alcohol Dications from Time-Resolved Molecular-Frame Photoelectron Angular Distributions
- Author
-
Kuraoka, T., primary, Goto, S., additional, Kanno, M., additional, Díaz-Tendero, S., additional, Reino-González, J., additional, Trinter, F., additional, Pier, A., additional, Sommerlad, L., additional, Melzer, N., additional, McGinnis, O. D., additional, Kruse, J., additional, Wenzel, T., additional, Jahnke, T., additional, Xue, H., additional, Kishimoto, N., additional, Yoshikawa, K., additional, Tamura, Y., additional, Ota, F., additional, Hatada, K., additional, Ueda, K., additional, and Martín, F., additional
- Published
- 2024
- Full Text
- View/download PDF
44. Combining Multiple Indices of Diffusion Tensor Imaging Can Better Differentiate Patients with Traumatic Brain Injury from Healthy Subjects [Corrigendum]
- Author
-
Abdelrahman HAF, Ubukata S, Ueda K, Fujimoto G, Oishi N, Aso T, and Murai T
- Subjects
Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 ,Neurology. Diseases of the nervous system ,RC346-429 - Abstract
Abdelrahman HAF, Ubukata S, Ueda K, et al. Neuropsychiatr Dis Treat. 2022;18:1801–1814. On page 1801, Abstract, Results, last sentence, the text “area under the curve of 93 ± 0.09” should read “area under the curve of 0.93 ± 0.09”. On page 1803, Imaging Acquisition section, line four, the text “64 non-collinear axis motion-probing gradients” should read “81 non-collinear axis motion-probing gradients”. On page 1803, Image Processing section, second paragraph, line seven, the text “was then thresholder at an FA value of 0.2” should read “was then thresholded at an FA value of 0.2”. On page 1803, Image Processing section, second paragraph, line two from the bottom, the text “Voxel-wise maps were thresholder at p < 0.05” should read “Voxel-wise maps were thresholded at p < 0.05”. The authors apologize for any inconvenience caused by these errors and for any confusion that may have arisen as a result. The authors would also like to assure the readers that these corrections do not affect the results or conclusions of the paper and are intended only to improve the accuracy of the methodology and data presentation.
- Published
- 2023
45. Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs
- Author
-
Alonso-Mori, R, Asa, K, Bergmann, U, Brewster, AS, Chatterjee, R, Cooper, JK, Frei, HM, Fuller, FD, Goggins, E, Gul, S, Fukuzawa, H, Iablonskyi, D, Ibrahim, M, Katayama, T, Kroll, T, Kumagai, Y, McClure, BA, Messinger, J, Motomura, K, Nagaya, K, Nishiyama, T, Saracini, C, Sato, Y, Sauter, NK, Sokaras, D, Takanashi, T, Togashi, T, Ueda, K, Weare, WW, Weng, T-C, Yabashi, M, Yachandra, VK, Young, ID, Zouni, A, Kern, JF, and Yano, J
- Subjects
Inorganic Chemistry ,Chemical Sciences ,Physical Chemistry ,Catalysis ,Crystallography ,X-Ray ,Electrons ,Lasers ,X-Rays ,Chemical Physics ,Chemical sciences - Abstract
The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.
- Published
- 2016
46. Pressure and magnetic-field effects on metal-insulator transitions of bulk and domain-wall states in pyrochlore iridates
- Author
-
Ueda, K., Fujioka, J., Terakura, C., and Tokura, Y.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
We have explored the critical metal-insulator phenomena for pyrochlore-type $R_2$Ir$_2$O$_7$, in which electron correlation strength and magnetic configuration are systematically controlled by varying the average rare-earth ionic radius ($R$=Nd$_{1-x}$Pr$_{x}$ and Sm$_{y}$Nd$_{1-y}$), external pressure, and magnetic field. Metal-insulator transitions in bulk are caused by increasing $x$ or tuning external pressure, indicating that the effective electron correlation is responsible for the transition. The metallic state intervenes between the paramagnetic insulating and antiferromagnetically ordered insulating phases for \SNIO ($y$=0.7-0.9), reminiscent of the first-order Mott transition. Furthermore, the metal-to-insulator crossover is observed (around $y$=0.7) for the charge transport on magnetic domain walls in the insulating bulk. An application of magnetic field also drives metal-insulator transitions for \NPIO in which a variety of exotic topological quantum states are potentially realized.
- Published
- 2015
- Full Text
- View/download PDF
47. Magnetic field-induced insulator-semimetal transition in a pyrochlore Nd2Ir2O7
- Author
-
Ueda, K., Fujioka, J., Yang, B. -J., Shiogai, J., Tsukazaki, A., Nakamura, S., Awaji, S., Nagaosa, N., and Tokura, Y.
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
We have investigated magneto-transport properties in a single crystal of pyrochore-type Nd2Ir2O7. The metallic conduction is observed on the antiferromagnetic domain walls of the all-in all-out type Ir-5d moment ordered insulating bulk state, that can be finely controlled by external magnetic field along [111]. On the other hand, an applied field along [001] induces the bulk phase transition from insulator to semimetal as a consequence of the field-induced modification of Nd-4f and Ir-5d moment configurations. A theoretical calculation consistently describing the experimentally observed features suggests a variety of exotic topological states as functions of electron correlation and Ir-5d moment orders which can be finely tuned by choice of rare-earth ion and by magnetic field, respectively.
- Published
- 2015
- Full Text
- View/download PDF
48. Centrifuge model tests and effective stress analyses of offshore wind turbine systems with a suction bucket foundation subject to seismic load
- Author
-
Ueda, K., Uzuoka, R., Iai, S., and Okamura, T.
- Published
- 2020
- Full Text
- View/download PDF
49. Migraine-Specific Quality-of-Life Questionnaire (MSQ) Version 2.1 Score Improvement in Japanese Patients with Episodic Migraine by Galcanezumab Treatment: Japan Phase 2 Study
- Author
-
Shibata M, Nakamura T, Ozeki A, Ueda K, and Nichols RM
- Subjects
mesh: preventive therapy ,quality of life ,Medicine (General) ,R5-920 - Abstract
Mamoru Shibata,1 Tomomi Nakamura,2 Akichika Ozeki,2 Kaname Ueda,2 Russell M Nichols3 1Department of Neurology, Tokyo Dental College Ichikawa General Hospital, Ichikawa, Japan; 2Medicines Development Unit Japan and Medical Affairs, Eli Lilly Japan K.K., Kobe, Japan; 3Global Medical Affairs, Eli Lilly and Company, Indianapolis, IN, USACorrespondence: Tomomi NakamuraMedicines Development Unit Japan and Medical Affairs, Eli Lilly Japan K.K., 5-1-28 Isogamidori, Chuo-Ku, Kobe 651-0086, JapanTel +81-78-242-9389Email nakamura_tomomi@lilly.comPurpose: Evaluate changes from baseline in health-related quality of life (QoL) in Japanese patients with episodic migraine receiving preventive treatment with galcanezumab (GMB).Patients and Methods: Preventive treatments for migraine have been shown to improve QoL, but few clinical trials have examined QoL outcomes in Japanese patients. This phase 2, randomized, double-blind, placebo-controlled study was conducted at 40 centers in Japan. Patients aged 18– 65 years with episodic migraine (4– 14 monthly migraine headache days) received GMB 120 mg (n=115), 240 mg (n=114), or placebo (PBO, n=230) as monthly subcutaneous injections for 6 months. QoL was measured monthly using the Migraine-Specific Quality-of-Life Questionnaire (MSQ) version 2.1. Prespecified analyses were differences between GMB and PBO for change from baseline in all 3 domains of the MSQ and MSQ-Total, for each month and the average over Months 4– 6.Results: Treatment with GMB significantly increased MSQ scores from baseline vs PBO. Average change ± SE from baseline across Months 4– 6 was 10.12± 0.72 (PBO), 17.13± 1.03 (GMB 120 mg; P< 0.001), and 15.91± 1.03 (GMB 240 mg; P< 0.001) for MSQ Role Function-Restrictive; 4.80± 0.65 (PBO), 9.64± 0.93 (GMB 120 mg; P< 0.001), and 8.35± 0.93 (GMB 240 mg; P< 0.05) for MSQ Role Function-Preventive (MSQ-RFP); 3.46± 0.77 (PBO), 10.04± 1.10 (GMB 120 mg; P< 0.001), and 7.73± 1.10 (GMB 240 mg; P< 0.05) for MSQ Emotional Function, and 7.14± 0.67 (PBO), 13.46± 0.95 (GMB 120 mg; P< 0.001), and 11.98± 0.95 (GMB 240 mg; P< 0.001) for MSQ-Total. Significantly greater improvement in scores in all MSQ domains and MSQ-Total was observed for both GMB doses vs PBO at Month 1 and was maintained for Months 1– 6 (excluding Month 5 for MSQ-RFP).Conclusion: Preventive treatment with GMB 120 mg/240 mg improves MSQ scores in Japanese patients with episodic migraine. Improvements were seen within the first month and maintained for 6 months and are similar to those seen in global studies enrolling primarily Caucasian patients.Clinical Trial Registration: ClinicalTrials.gov, NCT02959177 (registered November 7, 2016).Keywords: MeSH: preventive therapy, quality of life
- Published
- 2020
50. Fabrication of high-quality epitaxial Bi1-xSbx films by two-step growth using molecular beam epitaxy
- Author
-
Ueda, K., Hadate, Y., Suzuki, K., and Asano, H.
- Published
- 2020
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.