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Pacific Rim Conference on Lasers and Electro-Optics (CLEO/Pacific Rim)

作者： Liming Li S. Kusaka N. Karasawa R. Morita M. Yamashita Hokkaido University Japan Science and Technology Corporation Chitosc Japan Department of Applied Physics Core Research for Evolutional Science and Technology Sapporo Japan

The amplitude and phase of 5.0-fs optical pulses were characterized by a spectral phase interferometry for direct electric-field reconstruction (SPIDER) technique. This is the shortest pulse ever measured by the SPIDE... 详细信息

关键词： Optical pulses Optical interferometry Pulse measurements Pulse modulation Pulse amplifiers Optical pulse generation Optical modulation Chirp Delay physics

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Observation of Andreev Surface Bound States in the 3-K Phase Region of Sr2RuO4

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Physical Review Letters 2001年第3期87卷 037003-037003页

作者： Z. Q. Mao K. D. Nelson R. Jin Y. Liu Y. Maeno Department of Physics Kyoto University Kyoto 606-8502 Japan and Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation Kawaguchi Saitama 332-0012 Japan

The tunneling spectrum of the superconducting phase with Tc≃3.0K has been measured in the Ru-embedded region of Sr2RuO4 using cleaved junctions. A sharp zero-bias conductance peak (ZBCP) has been observed below 3 K. All characteristics of this ZBCP suggest that it originates from Andreev surface bound states, indicating that the pairing in the 3-K phase is also non- s-wave. Below the bulk Tc of Sr2RuO4 (≃1.5K), a crossover from sharp to bell-shaped ZBCP was found. This supports the theory that there is a phase transition in the 3-K phase region near the bulk Tc.

关键词： Superconductivity

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Ultrafast spin relaxation of excitons in a self-organized quantum-well material

Ultrafast spin relaxation of excitons in a self-organized qu...

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Quantum Electronics and Laser science Conference (QELS)

作者： J. Ishi Y. Kato K. Ohashi H. Kunugita K. Ema T. Ban T. Kondo Department of Physics Sophia University Chiyoda Tokyo Japan Core Research For Evolutional Science and Technology (CREST) Japan Science and Technology Corporation Japan

Summary form only given. Time-resolved photoluminescence and pump-probe spectroscopies have been employed to study the spin relaxation processes of excitons in bulk semiconductors and semiconductor quantum wells (QWs). Extensive studies have shown that the spin dynamics in QWs differs from that in the bulk. In spite of many studies on excitons with large Bohr-radius such as in GaAs-based QWs, studies on excitons with small Bohr-radius are lacking. Since spin relaxation greatly depends on the exchange interaction between electron and hole in the exciton, the spin dynamics is expected to change with the coupling strength between the electron and hole. Therefore, experiments for excitons with small Bohr-radius are desired for full understanding of spin phenomena in QWs.

关键词： Excitons Quantum wells Optical pumping Probes Nonlinear optics Ultrafast optics Optical pulses Magnetic confinement Delay Lattices

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NMR Evidence for Coexistence of Superconductivity and Ferromagnetic Component in Magnetic Superconductor RuSr2YCu2O8: R99,101u and C63u NMR

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Physical Review Letters 2001年第25期86卷 5767-5767页

作者： Y. Tokunaga H. Kotegawa K. Ishida Y. Kitaoka H. Takagiwa J. Akimitsu Department of Physical Science Graduate School of Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Corporation (JST) Department of Physics Aoyama-Gakuin University Setagaya-ku Tokyo 157-8572 Japan

From Ru- and Cu-NMR studies, we present evidence for coexistence of superconductivity and ferromagnetism in a cuprate superconductor RuSr2YCu2O8 (RuY1212). The observation of a large enhancement of a radio-frequency field for the Ru-NMR signal at zero field reveals the existence of a ferromagnetic (FM) component in the ordered RuO2 plane below a Curie temperature of TM=150K. Just below the onset temperature of superconductivity Tconset=45K, a remarkable decrease of the nuclear spin-lattice relaxation rate 1/T1 was observed within the ordered RuO2 plane as well as the CuO2 plane, revealing that the superconducting gap coexists with the FM component in the RuO2 plane on a microscopic scale. In addition, from the observation of a sharp peak in 101(1/T1) at Tczero∼23K where the resistivity becomes zero, we suggest that the motion of self-induced vortices originating from fluctuations of the FM component induces the resistivity between Tconset and Tczero in RuY1212.

关键词： Superconducting materials

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Dielectric and magnetic anomalies and spin frustration in hexagonal RMnO3 (R=Y, Yb, and Lu)

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Physical Review B 2001年第10期64卷 104419-104419页

作者： T. Katsufuji S. Mori M. Masaki Y. Moritomo N. Yamamoto H. Takagi Department of Advanced Materials Science and Department of Applied Chemistry University of Tokyo Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation Japan Department of Physics Tokyo Institute of Technology Tokyo 152-8551 Japan CIRSE and Department of Crystalline Materials Science Nagoya University Nagoya 464-8601 Japan

Single crystals of hexagonal RMnO3 (R=Y, Yb, and Lu), where Mn ions form the triangular lattice, were investigated, focusing on their dielectric/magnetic anomalies as well as geometrical spin frustration. It is found that the ratio of a Weiss temperature to TN is ∼10 in RMnO3, indicating the dominant role of strong geometrical frustration. The effect of geometrical frustration also appears in specific heat, which shows a presence of a substantial amount of residual magnetic contribution below TN, indicating that a part of the spins are still fluctuating at T≪TN. It is also found that the dielectric anomaly at TN is strongly anisotropic, suggesting a unique correlation between magnetism and dielectric properties in these compounds.

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Evidence for Strong-Coupling s-Wave Superconductivity in MgB2: B11 NMR Study

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Physical Review Letters 2001年第12期87卷 127001-127001页

作者： H. Kotegawa K. Ishida Y. Kitaoka T. Muranaka J. Akimitsu Department of Physical Science Graduate School of Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Corporation (JST) Kawaguchi Saitama 332-0012 Japan Department of Physics Aoyama-Gakuin University Setagaya-ku Tokyo 157-8572 Japan

We have investigated a gap structure in a newly discovered superconductor, MgB2, through measurement of the 11B nuclear spin-lattice relaxation rate, 11(1/T1). 11(1/T1) is proportional to the temperature (T) in the normal state, and decreases exponentially in the superconducting (SC) state, revealing a tiny coherence peak just below Tc. The T dependence of 1/T1 in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Δ/kBTc∼5 which suggests it is in a strong-coupling regime.

关键词： Superconducting materials

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High-Pressure Mssbauer Study of Perovskite Iron Oxide

High-Pressure Mssbauer Study of Perovskite Iron Oxide

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18th International Conference on High Pressure science and technology

作者： T.Kawakami T.Sasaki S.Morimoto S.Nasu S.Endo S.Kawasaki M.Takano Division of Materials Physics Department of Physical Science Graduate School of Engineering Science Osaka 560-8531 Japan Division of Materials Physics Department of Physical Science Graduate School of Engineering Science Osaka 560-8531 Japan Division of Materials Physics Department of Physical Science Graduate School of Engineering Science Osaka 560-8531 Japan Division of Materials Physics Department of Physical Science Graduate School of Engineering Science Osaka 560-8531 Japan Core Research for Evolutional Science and Technology(CREST Research Center for Materials Science at Extreme Conditions Osqka University Toyonaka Osaka 560-8531 Japan Core Research for Evolutional Science and Technology(CREST Institute for Chemical Research Kyoto University Uji Kyoto-fu 611-0011 Japan Institute for Chemical Research Kyoto University Uji Kyoto-fu 611-0011 Japan

High valent states of Fein CaFeO and Fein LaSrFeO of the perovskite iron oxide whichshow a strong hybridization between Fe（3d） andO（2p） play an important role on their magneticordering,electrical conductivity and charge ordering. Using a diamond anvil cell,Fe Mossbauermeasurements have been carried out on theperovskite oxide CaFeO under high pressure up to65 GPa at various *** criticaltemperature of a charge disproportionation(CD:2Fe=Fe+Fe) and a magnetic ordering havebeen determined as a function of *** CD

关键词： High-pressure 57Fe Mossbauer spectro-scopy, charge disproportionation, CaFeO3,La1/3Sr2/3FeO3.

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Ab initio study of hydrogen adsorption to single-walled carbon nanotubes

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Physical Review B 2001年第15期63卷 155405-155405页

作者： K. Tada S. Furuya K. Watanabe Department of Physics Science University of Tokyo 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan Frontier Research Center for Computational Sciences Science University of Tokyo 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation 4-1-8 Honmachi Kawaguchi Saitama 332-0012 Japan

We perform the density-functional and quantum chemical calculations of adsorption of a hydrogen molecule to various kinds of single-walled carbon nanotubes (SWNT’s). The potential energy barrier height (PBH) for the dissociative adsorption of a hydrogen molecule onto the outer wall of a nanotube decreases as the tube diameter decreases. In contrast, the PBH for H2 penetration into an open-ended nanotube increases as the tube diameter decreases, independent of the atomic geometry, i.e., zigzag or armchair structures. H2, however, cannot adsorb to the inner wall of any type of nanotube. These results on the structure-dependent H2 adsorption to SWNT’s are reasonably explained by the sp2−sp3 rehybridization caused by the interaction between the adsorbing hydrogen and carbon atoms of SWNT’s.

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Sign reversal of the oxygen isotope effect on Tc in Sr2RuO4

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Physical Review B 2001年第14期63卷 144514-144514页

作者： Z. Q. Mao Y. Maeno Y. Mori S. Sakita S. Nimori M. Udagawa Department of Physics Kyoto University Kyoto 606-8502 Japan Core Research for Evolutional Science and Technology Japan Science and Technology Corporation (CREST-JST) Kawaguchi Saitama 332-0012 Japan Venture Business Laboratory Hiroshima University Higashi-Hiroshima 739-8527 Japan Faculty of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima 739-8521 Japan

We investigated the oxygen isotope effect (IE) on the transition temperature Tc in the spin-triplet superconductor Sr2RuO4 (with the intrinsic Tc0=1.5K). A clear IE shift in Tc was observed. Moreover, we found that the IE coefficient alpha exhibits an unusual variation with Tc. For lower-Tc crystals containing impurities and defects, α is positive and increases with decreasing Tc; α(Tc) is described well by the universal behavior expected theoretically. However, for crystals with Tc approaching Tc0, α deviates from the universal α(Tc) and becomes negative. We discuss its possible mechanism on the basis of existing models.

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Partitioned Real-Space Density Functional Calculations of Bielectrode Systems under Bias Voltage and Electric Field

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Physical Review Letters 2001年第3期86卷 540-540页

作者： N. Nakaoka K. Tada S. Watanabe H. Fujita K. Watanabe Department of Physics Science University of Tokyo 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan Department of Material Science University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation Institute of Industrial Science University of Tokyo 7-22-1 Roppongi Minato-ku Tokyo 106-8558 Japan Frontier Research Center for Computational Sciences Science University of Tokyo 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan

We have developed a new partitioned real-space density functional (PRDF) method and applied it to bielectrode systems under bias voltage and electric field. The electronic states, electrostatic potentials, local electric fields, and chemical potentials of biased jelliums and two Si5 clusters are fully self-consistently determined. We overcame an essential difficulty in obtaining the electronic states of biased systems from the conventional density functional method by dividing the entire system into subsystems of each electrode. The PRDF method can be applied to multielectrode systems and enables the investigation of ionic systems with computational efficiency.

关键词： Electronic structure

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