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Efficient and accurate linear algebraic methods for large-scale electronic structure calculations with nonorthogonal atomic orbitals

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Physical Review B 2011年第16期83卷 165103-165103页

作者： H. Teng T. Fujiwara T. Hoshi T. Sogabe S.-L. Zhang S. Yamamoto Center for Research and Development of Higher Education The University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology Japan Science and Technology Agency (CREST-JST) Japan Department of Applied Mathematics and Physics Tottori University Tottori 680-8550 Japan School of Information Science and Technology Aichi Prefecture University Nagakute-cho Aichi 480-1198 Japan Department of Computational Science and Engineering Nagoya University Chikusa-ku Nagoya 464-8603 Japan School of Computer Science Tokyo University of Technology Katakura-machi Hachioji Tokyo 192-0982 Japan

The need for large-scale electronic structure calculations arises recently in the field of material physics, and efficient and accurate algebraic methods for large simultaneous linear equations become greatly important. We investigate the generalized shifted conjugate orthogonal conjugate gradient method, the generalized Lanczos method, and the generalized Arnoldi method. They are the solver methods of large simultaneous linear equations of the one-electron Schrödinger equation and map the whole Hilbert space to a small subspace called the Krylov subspace. These methods are applied to systems of fcc Au with the NRL tight-binding Hamiltonian [F. Kirchhoff et al., Phys. Rev. B 63, 195101 (2001)]. We compare results by these methods and the exact calculation and show them to be equally accurate. The system size dependence of the CPU time is also discussed. The generalized Lanczos method and the generalized Arnoldi method are the most suitable for the large-scale molecular dynamics simulations from the viewpoint of CPU time and memory size.

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Universality of superconducting gaps in overdoped Ba0.3K0.7Fe2As2 observed by angle-resolved photoemission spectroscopy

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Physical Review B 2011年第2期83卷 020501(R)-020501(R)页

作者： K. Nakayama T. Sato P. Richard Y.-M. Xu T. Kawahara K. Umezawa T. Qian M. Neupane G. F. Chen H. Ding T. Takahashi Department of Physics Tohoku University Sendai 980-8578 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency (JST) Kawaguchi 332-0012 Japan Transformative Research Project on Iron Pnictides (TRiP) Japan Science and Technology Agency (JST) Kawaguchi 332-0012 Japan World Premier International Research Center Advanced Institute for Materials Research Tohoku University Sendai 980-8577 Japan Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics Boston College Chestnut Hill Massachusetts 02467 USA Department of Physics Renmin University of China Beijing 100872 China

We have performed angle-resolved photoemission spectroscopy on the overdoped Ba0.3K0.7Fe2As2 superconductor (Tc=22 K). We demonstrate that the superconducting (SC) gap on each Fermi surface (FS) is nearly isotropic whereas the gap value varies from 4.4 to 7.9 meV on different FSs. By comparing with under- and optimally doped Ba1−xKxFe2As2, we find that the gap value on each FS nearly scales with Tc over a wide doping range (0.25⩽x⩽0.7). Although the FS volume and the SC gap magnitude are strongly doping dependent, the multiple nodeless gaps can be commonly fitted by a single gap function assuming pairing up to the second nearest neighbor, suggesting the universality of the short-range pairing states with the s±-wave symmetry.

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Beamlike photon pairs entangled by a 2×2 fiber

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Physical Review A 2011年第2期84卷 022301-022301页

作者： Hsin-Pin Lo Atsushi Yabushita Chih-Wei Luo Pochung Chen Takayoshi Kobayashi Department of Physics National Tsing Hua University Hsinchu 300 Taiwan Republic of China Department of Electrophysics National Chiao-Tung University Hsinchu 300 Taiwan Republic of China Core Research for Evolutional Science and Technology Japan Science and Technology Agency 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan University of Electro-Communications 1-5-1 Chofugaoka Chofu Tokyo 182-8585 Japan Institute of Laser Engineering Osaka University 2-6 Yamada oka Suita Osaka 565-0971 Japan

Polarization-entangled photon pairs have been widely used as a light source of quantum communication. The polarization-entangled photon pairs are generally obtained at the crossing points of the light cones that are generated from a type-II nonlinear crystal. However, it is hard to pick up the photon pairs coming out from the crossing points because of their invisible wavelength and low intensity. In our previous work, we succeeded in generating polarization-entangled photon pairs by overlapping two light paths for the photon-pair generation. The photon pairs could be entangled in all of the generated photon pairs without clipping the crossing points, even with some difficulty in its alignment to overlap the two light paths. In this paper, we have developed an optical system which generates polarization-entangled photon pairs using a beamlike photon pair, without the difficulty in alignment. The measured results show that the photon pairs generated in the system are entangled in their polarizations.

关键词： Polarization

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Competition between instabilities of Peierls transition and Mott transition in W-doped VO2 thin films

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Physical Review B 2011年第19期84卷 195132-195132页

作者： Enju Sakai Kohei Yoshimatsu Keisuke Shibuya Hiroshi Kumigashira Eiji Ikenaga Masashi Kawasaki Yoshinori Tokura Masaharu Oshima Department of Applied Chemistry University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency (JST) Bunkyo-ku Tokyo 113-8656 Japan Cross-Correlated Materials Research Group (CMRG) Advanced Science Institute RIKEN Wako 351-0198 Japan PRESTO Japan Science and Technology Agency (JST) Kawaguchi Saitama 332-0012 Japan Synchrotron Radiation Research Organization University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan JASRI/SPring-8 Mikazuki-cho Hyogo 679-5198 Japan World Premier International-Advanced Institute for Materials Research (WPI-AIMR) Tohoku University Sendai 980-8577 Japan Department of Applied Physics and Quantum-Phase Electronics Center University of Tokyo Tokyo 113-8656 Japan Multiferroics Project ERATO Japan Science and Technology Agency (JST) Tokyo 113-8656 Japan

The change in electronic structure of V1−xWxO2 thin films across a metal-insulator transition (MIT) is investigated in terms of hard x-ray photoemission spectroscopy and x-ray absorption spectroscopy. In the lower doping range (0 ≤ x ≤ 0.08), the spectra exhibit the characteristic features for the dimerization of V ions in the monoclinic phase, indicating that Peierls-like instability predominately causes the MIT in this range. Conversely, in the higher doping range (0.1 ≤ x), spectral weight transfer is observed from the coherent part at the Fermi level to the incoherent part, indicating that the ground state of V1−xWxO2 films in this range is a typical Mott insulator. The results suggest that the unusual phase diagram of the V1−xWxO2 thin films originates from the competition between the Peierls and Mott instabilities.

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Femtosecond pulse cleaning and measurement using self-diffraction process

Femtosecond pulse cleaning and measurement using self-diffra...

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International Conference on Quantum Electronics (IQEC)

作者： Jun Liu Takayoshi Kobayashi Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency Kawaguchi Saitama Japan State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai China Advanced Ultrafast Laser Research Center University of Electro-Communications Chofu Tokyo Japan Institute of Laser Engineering Osaka University Ibaraki Japan Department of Electrophysics National Chiao Tung University Hsinchu Taiwan

The self-diffraction effect was used to improve temporal contrast of femtosecond pulse by about four-order of magnitudes. This self-diffraction effect was also used to measure a 55fs pulse based on the self-referenced... 详细信息

ISBN: (纸本)9780977565771

关键词： Pulse measurements Measurement by laser beam Solids Laser beams Interferometry Delay Signal resolution

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Surface ligand assisted valence change in ceria nanocrystals

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Physical Review B 2011年第4期84卷 045411-045411页

作者： J. Zhang T. Naka S. Ohara K. Kaneko T. Trevethan A. Shluger T. Adschiri Institute of Multidisciplinary Research for Advanced Materials Tohoku University Sendai 980-8577 Japan National Institute for Materials Science Tsukuba Ibaraki 305-0047 Japan Joining and Welding Research Institute Osaka University Ibaraki Osaka 567-0047 Japan Department of Materials Science & Engineering Kyushu University Fukuoka 819-0395 Japan Core Research for Evolutional Science and Technology Kyushu University Fukuoka 819-0395 Japan WPI-Advanced Institute for Materials Research Tohoku University Sendai 980-8577 Japan Department of Physics and Astronomy University College London Gower Street London WC1E 6BT United Kingdom

In this report, we used x-ray absorption, electron energy-loss, and magnetic analyses to demonstrate the effect of modification of ceria (CeO2−δ) nanocrystals with a particle size D = 3.5–14 nm by oleic acid surface ligands. We observe a shift of the electronic state of the cerium ions from tetra to trivalent state as the surface density of the ligand molecules is increased. The valence state of cerium in the nanocrystal is strongly correlated with the number of ligand molecules bound to the surface of the ceria nanocrystals. One oxygen vacancy is stabilized by 5–6 ligand molecules bound on a CeO2−δ nanocrystal.

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Completely characterizing single attosecond pulses by the modified spectral phase interferometry

Completely characterizing single attosecond pulses by the mo...

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International Conference on Ultrafast Phenomena, UP 2010

作者： Zhu, J. Fang, S. Yamane, K. Chen, T. Yamashita, M. Department of Applied Physics Hokkaido University Core Research for Evolutional Science and Technology Japan Science and Technology Agency Kita-13 Nishi-8 Kita-ku Sapporo 060-8628 Japan

Complete characterization of single attosecond pulses by the modified spectral phase interferometry is presented considering the frequency-dependent spectral shear. The results show no principle limitation of characte...

ISBN: (纸本)9781557528940

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The development of angularly-dispersed non-collinear optical parametric amplifier for generation of high power optical pulses in monocycle regime

The development of angularly-dispersed non-collinear optical...

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International Conference on Ultrafast Phenomena, UP 2010

作者： Yamane, Keisaku Tanigawa, Takashi Sekikawa, Taro Yamashita, Mikio Department of Applied Physics Hokkaido University Core Research Evolutional Science and Technology Japan Science and Technology Agency Kita-13 Nishi-8 Kita-ku Sapporo 060-8628 Japan

We greatly improved our angularly-dispersed NOPA system and introduced a new stretcher for seed pulses. Consequently, we achieved the broadest gain bandwidth ranging from 500 to 1030 nm with output pulse energy of 45 ... 详细信息

ISBN: (纸本)9781557528940

关键词： Optical parametric amplifiers

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Complete characterization of single attosecond pulses by the modified spectral phase interferometry with an all-optical apparatus

Complete characterization of single attosecond pulses by the...

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作者： Zhu, J. Fang, S. Chen, T. Yamane, K. Yamashita, M. Department of Applied Physics Hokkaido University and Core Research for Evolutional Science and Technology Japan Science and Technology Agency Kita-13 Nishi-8 Kita-ku Sapporo 060-8628 Japan

We present the complete characterization of single attosecond pulses by the modified SPIDER method with a frequency-dependent spectral shear. The validity of this method shows no principle limitation of characterizing...

ISBN: (纸本)9781557528902

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Ultra-broadband spectral-shifted pulse pair generation by amplitude modulation for single attosecond pulse characterization using the SPIDER method

Ultra-broadband spectral-shifted pulse pair generation by am...

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Conference on Lasers and Electro-Optics (CLEO)

作者： J. Zhu T. Tanigawa T. Chen S. Fang K. Yamane M. Yamashita Department of Applied Physics Core Research for Evolutional Science and Technology Japan Science and Technology Agency Hokkaido University Sapporo Japan

Ultra-broadband amplitude modulation for spectral-shifted pulse pair generation is realized by a liquid-crystal spatial light modulator. The results indicate that it's a promising way for single attosecond pulse c... 详细信息

ISBN: (纸本)9781557528896

关键词： Pulse modulation Character generation Pulse generation Amplitude modulation Pulse amplifiers Optical pulse generation Bandwidth Optical modulation Optical pulse shaping Mirrors

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