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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： Eiichi Matsubara Ryuji Morita Taro Sekikawa Mikio Yamashita Department of Applied Physics Core Research for Evolutional Science and Technology Japan Science and Technology Agency Hokkaido University Sapporo Japan

The purpose of this study is to generate sub-femtosecond class optical pulses using multiple coherent anti-Stokes Raman scattering (CARS) signals in solids at room temperature.

关键词： Optical pulse generation Signal generators Optical pulses Pulse measurements Physics Solids Temperature Optical refraction Pulse amplifiers Pulse generation

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Preparation, crystal structure and thermoelectric properties of La2−2xCa1+2xMn2O7

Preparation, crystal structure and thermoelectric properties...

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International Conference on Thermoelectrics (ICT)

作者： Yuzuru Miyazaki Daisuke Abe Tsuyoshi Kajitani Department of Applied Physics Graduate School of Engineering Tohoku University Sendai Japan Core Research for Evolutional Science and Technology Japan Science and Technology Agency Chuo Tokyo Japan

We have prepared polycrystalline samples of the Ruddlesden-Popper La 2-2x Ca 1+2x Mn 2 O 7 phase and determined their crystal structure and thermoelectric properties above room temperature. Single-phase samples with tetragonal I4/mmm space group are obtained for the samples with 0.50 les x les 1.00; the corresponding valence state of Mn is from 3.5 to 4.0. With increasing x, the a-axis length gradually decreases from 3.8268(4) Aring (x = 0.5) to 3.7078(2) Aring (x = 1.0), while the c-axis length increases from 19.197(3) Aring(x = 0.5) to 19.438(1) Aring(x = 1.0). As expected, all the samples exhibit negative Seebeck coefficients, S. The absolute value of S increases with increasing x, and the phases become electrically conductive at high temperatures. For example, the sample with x = 0.50 exhibits the electrical conductivity, sigma = 35 S/cm and S = -40muV/K at 1123 K, compared with those of the sample with x = 0.95 of sigma = 18 S/cm and S = -175 muV/K. The highest ZT ~0.03 with the power factor of 5.5 x 10 -5 W/mK 2 , has been obtained for the x = 0.95 sample at 1123 K.

关键词： Thermoelectricity Tellurium Temperature Space technology Thermal conductivity X-ray diffraction Atomic measurements Powders X-ray scattering Conductivity measurement

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Electronic structure of charge and spin stripe order in La2−xSrxNiO4 (x=13,12)

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Physical Review B 2007年第16期76卷 165114-165114页

作者： Susumu Yamamoto Takeo Fujiwara Yasuhiro Hatsugai Core Research for Evolutional Science and Technology Japan Science and Technology Corporation (CREST-JST) Japan Center for Research and Development of Higher Education University of Tokyo Tokyo 113-8656 Japan Institute of Physics University of Tsukuba 1-1-1 Tennodai Tsukuba Ibaraki 305-8571 Japan Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan

Electronic structure of stripe ordered La2−xSrxNiO4 is investigated. The system with x=13 is insulator, in LSDA+U calculations, and shows charge and spin stripe, consistent with the experimental results. A highly correlated system of x=12 is studied by using exact diagonalization of the multiorbital many-body Hamiltonian derived from LDA calculations and including on-site and intersite Coulomb interactions. The fluctuation of the residual spin on Ni3+ (hole) site couples with the charge fluctuation between Ni3+ and Ni2+ states and this correlation lowers the total energy. The resultant ground state is an insulator with charge and spin stripe of the energy gap 0.9eV, consistent with the observed one. The on-site Coulomb interaction stabilizes integral valency of each Ni ion (Ni3+ and Ni2+), but does not induce the charge order. Two quantities, intersite Coulomb interaction and anisotropy of hopping integrals, play an important role to form the charge and spin stripe order in a system of x=12.

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Purification of single qubits by collinear photons

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Physical Review A 2007年第3期75卷 034306-034306页

作者： Satoru Odate Yuishi Takeno Takayoshi Kobayashi Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation (JST) Department of Physics Graduate School of Science The University of Tokyo Hongo 7-3-1 Bunkyo Tokyo 113-0033 Japan Department of Applied Physics and Chemistry Institute of Laser Research The University of Electro-Communications Chofugaoka 1-5-1 Chofu Tokyo 182-8585 Japan Institute of Laser Engineering Osaka University Yamada-oka 2-6 Suita Osaka 565-0971 Japan and Department of Electrophysics National Chiao-Tung University Hsinchu 3005 Taiwan

We have demonstrated purification of a single qubit by two collinear photons, one of which was time-delayed. Our method can be applied to a single qubit many times, and the qubit can be purified to an arbitrarily high degree of purity. Thus, by repeating this method we can make the statistical error that single qubits incur along a transmission channel much smaller.

关键词： ENTANGLEMENT PURIFICATION

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A Tungsten–Tin Mixed Hydroxide as an Efficient Heterogeneous Catalyst for Dehydration of Aldoximes to Nitriles†

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Angewandte Chemie 2007年第21期119卷

作者： Kazuya Yamaguchi Hiroshi Fujiwara Yoshiyuki Ogasawara Miyuki Kotani Noritaka Mizuno Department of Applied Chemistry School of Engineering The University of Tokyo 7‐3‐1 Hongo Bunkyo‐ku Tokyo 113‐8656 Japan Fax: (+81) 3‐5841‐7220 Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency (JST) 4‐1‐8 Honcho Kawaguchi Saitama 332‐0012 Japan

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Thermogravimetric Study and High-Temperature Thermoelectric Properties of [Ca2(Co1-xAx)O3]0.62CoO2

Thermogravimetric Study and High-Temperature Thermoelectric ...

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International Conference on Thermoelectrics (ICT)

作者： Y. Oide Y. Miyazaki Y. Ono X. Y. Huang T. Kajitani Department of Applied Physics Graduate School of Engineering University of Tohoku Sendai Japan Core Research for Evolutional Science and Technology Japan Science and Technology Agency Chuo Tokyo Japan

Systematic ion substitution has been performed on the Co site in the rock-salt (RS)-type [Ca 2 CoO 3 ] subsystem of misfit-layered cobalt oxide [Ca 2 (Co 1-x A x )O 3-delta ] 0.62 CoO 2 (A = Nb, Ru, Ta, Pb, W, La and Zr). The oxygen deficiency delta and the decomposition temperature T d of the substituted samples have been determined by means of the thermogravimetric analysis (TGA). Upon heating, the oxygen atoms are gradually released from the RS-type subsystem up to delta~0.10. A small amount (x = 0.10) of the substitution remarkably increases T d from 1173 K (x = 0) up to 1246 K (A = Nb). The Pb-substituted samples show substantial decrease in electrical resistivity p from 19.2 mOmegacm to 13.8 mOmegacm (x = 0.10) at 950 K. The highest thermoelectric power, S 2 p -1 = 2.1times10 -4 WK -2 m -1 , is realized for the Pb-substituted sample with x = 0.10 at 950 K

关键词： Thermoelectricity Niobium Zirconium Cobalt Heating Electric resistance Temperature dependence Powders X-ray scattering Physics

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Theory of large-scale electronic structure calculation and nanoscale mechanical property in fracture behavior of silicon

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MRS Online Proceedings Library 2006年第1期880卷 1-6页

作者： Takeo Hoshi Ryu Takayama Yusuke Iguchi Takeo Fujiwara Department of Applied Physics University of Tokyo Hongo Bunkyo-ku Tokyo Japan Core Research for Evolutional Science and Technology (CREST-JST) Japan Science and Technology Agency Honcho Kawaguchi-shi Saitama Japan Research and Development for Applying Advanced Computational Science and Technology (ACT-JST) Japan Science and Technology Agency USA

Several theories and program codes were developed for large-scale atomistic simulations with fully quantum mechanical description of electron systems. The fundamental concepts are generalized Wannier state and Krylov subspace. Test calculations were carried out with upto 106 atoms using a standard workstation. How electronic state is described in large-scale calculation was demonstrated on Si(001)-(2×1) surface. As a practical application, cleavage fracture of silicon was simulated with 10-nm-scale samples for investigating its nanoscale mechanical behavior. Discussions are focused on the unstable (001) cleavage mode and the stable (experimentally observed) (111)-(2×1) cleavage mode. As well as elementary surface reconstruction, step formation and bending in cleavage path were observed. These results were compared with experiments, such as scanning tunneling microscope (STM).

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Linear algebraic calculation of the Green’s function for large-scale electronic structure theory

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Physical Review B 2006年第16期73卷 165108-165108页

作者： R. Takayama T. Hoshi T. Sogabe S.-L. Zhang T. Fujiwara Research and Development for Applying Advanced Computational Science and Technology (ACT-JST) Japan Science and Technology Agency 4-1-8 Honcho Kawaguchi-shi Saitama 332-0012 Japan Department of Applied Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology (CREST-JST) Japan Science and Technology Agency 4-1-8 Honcho Kawaguchi-shi Saitama 332-0012 Japan

A linear algebraic method named the shifted conjugate-orthogonal conjugate-gradient method is introduced for large-scale electronic structure calculation. The method gives an iterative solver algorithm of the Green’s function and the density matrix without calculating eigenstates. The problem is reduced to independent linear equations at many energy points and the calculation is actually carried out only for a single energy point. The method is robust against the round-off error and the calculation can reach the machine accuracy. With the observation of residual vectors, the accuracy can be controlled, microscopically, independently for each element of the Green’s function, and dynamically, at each step in dynamical simulations. The method is applied to both a semiconductor and a metal.

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Electronic structure of antiferromagnetic LaMnO3 and the effects of charge polarization

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Physical Review B 2006年第6期74卷 064417-064417页

作者： Y. Nohara A. Yamasaki S. Kobayashi T. Fujiwara Department of Applied Physics University of Tokyo Tokyo 113-8656 Japan Max-Planck Institut für Festkörperforschung Heisenbergstrasse 1 Stuttgart D-70569 Germany Texas Instruments Japan Ltd. 6-24-1 Nishi-Shinjuku Shinjuku-ku Tokyo 160-8366 Japan Core Research for Evolutional Science and Technology (CREST-JST) Japan Science and Technology Corporation (JST) Japan

The electronic structure of A-type antiferromagnetic insulator LaMnO3 is investigated by the GW approximation. The band gap and spectrum are in a good agreement with experimental observation. The lifetime of electrons in conduction bands is much shorter than that of holes in valence bands. The insulator-to-metal transition with antiferromagnetic-to-ferromagnetic transition with photocarrier injection is attributed to the characteristic properties of excited electron states in A-type antiferromagnetic perovskite systems. The onsite d−d Coulomb interaction is strongly screened at the low energy region by mobile eg electrons.

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Formation of S‐Shaped Disilicoicosatungstate and Efficient Baeyer–Villiger Oxidation with Hydrogen Peroxide†

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Angewandte Chemie 2006年第12期118卷

作者： Akihiro Yoshida Masayuki Yoshimura Kazuhiro Uehara Shiro Hikichi Noritaka Mizuno Department of Applied Chemistry School of Engineering The University of Tokyo 7‐3‐1 Hongo Bunkyo‐ku Tokyo 113‐8656 Japan Fax: (+81) 3‐5841‐7220 Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency (JST) 4‐1‐8 Honcho Kawaguchi Saitama 332‐0012 Japan

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