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Dispersion and Damping of a Two-Dimensional Plasmon in a Metallic Surface-State Band

Physical Review Letters 2001年第25期86卷 5747-5747页

作者： Tadaaki Nagao Torsten Hildebrandt Martin Henzler Shuji Hasegawa Department of Physics Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan Precursory Research for Embryonic Science and Technology (PRESTO) Japan Science and Technology Corporation (JST) 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation (JST) 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Institut für Festkörperphysik der Universität Hannover Appelstraße 2 D-30167 Hannover Germany

We have studied, for the first time, the energy and the linewidth dispersion of a plasmon in a dense two-dimensional electron system in a metallic surface-state band on a silicon surface. As expected from the considerably high effective density and long Fermi wavelength of the system, the plasmon energy dispersion exhibited an excellent agreement with the nearly free-electron theory. However, in a small wave number region below the Landau edge, we have observed an anomalous linewidth dispersion which nearly free-electron theories do not predict.

关键词： Plasma theory

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Dynamics of the cantilever in noncontact dynamic force microscopy: The steady-state approximation and beyond

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Physical Review B 2001年第8期64卷 085409-085409页

作者： M. Gauthier N. Sasaki M. Tsukada Department of Physics Graduate School of Science University of Tokyo Hongo 7-3-1 Bunkyo-ku Tokyo 113-0033 Japan Department of Materials Engineering Graduate School of Engineering University of Tokyo Hongo 7-3-1 Bunkyo-ku Tokyo 113-8656 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation (JST) 2-1-6 Sengen Tsukuba Ibaraki 305-0047 Japan

A detailed analysis of models that have been used for describing the dynamics of the cantilever in large-amplitude noncontact dynamic force microscopy is presented. For each model, attention is especially paid to the nonlinear nature of the problem and its implication for experiments. In particular, in the steady-state approximation where the equations of motion for an externally and self-driven oscillator are rigorously identical, the theory predicts the existence of unstable solutions whether the interaction force is dissipative or not. The need to go beyond the steady-state approximation by including the finite-time response of the system to a change of tip-surface separation or interaction during the scanning is also discussed.

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Electronic structure of Ag-induced 3×3 and 21×21 superstructures on the Si(111) surface studied by angle-resolved photoemission spectroscopy and scanning tunneling microscopy

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Physical Review B 2001年第20期64卷 205316-205316页

作者： Xiao Tong Satoru Ohuchi Norio Sato Takehiro Tanikawa Tadaaki Nagao Iwao Matsuda Yoshinobu Aoyagi Shuji Hasegawa The Institute of Physical and Chemical Research (RIKEN) 2-1 Hirosawa Wako Saitama 351-0198 Japan Department of Physics University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan Core Research for Evolutional Science and Technology The Japan Science and Technology Corporation Kawaguchi Center Building Hon-cho 4-1-8 Kawaguchi Saitama 332-0012 Japan Department of Chemistry University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan

Polarization-dependent angle-resolved photoemission spectroscopy was used to analyze the electronic band structure of the Si(111)−21×21(R±10.89°)−Ag surface induced by adding submonolayer Ag atoms on top of the Si(111)-3×3-Ag surface at 140 K, together with a refinement of the electronic states of the initial 3×3-Ag substrate itself. The surface-state band crossing the Fermi level on the the 3×3-Ag surface was found to have similar dispersions in both Γ¯−K¯ and Γ¯−M¯ directions around the Γ¯ point of the 3×3 surface Brillouin zone, and consist mainly of components parallel to the surface with no measurable polarization dependence. The five intrinsic surface-state bands observed on the 3×3-Ag surface basically remained in the 21×21-Ag structure, but shifted down in energy position from the Fermi level by about 0.4 eV. This is due to electron transfer from the Ag adatoms to the substrate, suggesting that the Ag adatoms in the 21×21-Ag phase sit on a nearly unaltered 3×3-Ag substrate, and do not make any orbital hybridization with the substrate. Only one parabolic band crossing the Fermi level was found on the 21×21-Ag surface, for which distribution in real space is observed by bias-dependent scanning tunneling microscopy. This result is in contrast to two metallic bands on the 21×21 phase induced by Au or Cu adatoms on the 3×3-Ag substrate reported in previous papers.

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Simultaneous coherent multicolor pulse shaping using two-dimensional spatial light amplitude- and phase-modulator for multi-selective wave-packet control

Simultaneous coherent multicolor pulse shaping using two-dim...

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Nonlinear Optics: Materials, Fundamentals and Applications

作者： R. Morita N. Kameya M. Yamashita A. Suguro H. Shigekawa Department of Applied Physics Japan Science and Technology Corporation Hokkaido University and Core Research for Evolutional Science and Technology Sapporo Japan Display Development Technical Research Laboratory Citizen Watch Company Limited Tokorozawa Japan Institute of Applied Physics and Core Research for Evolutional Science and Technology Japan Science and Technology Corporation University of Tsukuba Tsukuba Japan

Using a two-dimensional spatial light amplitude and phase-modulator, simultaneous multicolor pulse shaping of coherent ultrabroadband (600 to 850 nm) optical pulses generated by self-phase modulation in an Ar-gas fill... 详细信息

ISBN: (纸本)1557526451

关键词： Pulse shaping methods Optical pulses Optical pulse generation Phase modulation Amplitude modulation Optical modulation Pulse modulation Shape control Optical control Lighting control

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In-Plane Anisotropy of Upper Critical Field in Sr2RuO4

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Physical Review Letters 2000年第5期84卷 991-991页

作者： Z. Q. Mao Y. Maeno S. NishiZaki T. Akima T. Ishiguro Department of Physics Kyoto University Kyoto 606-8502 Japan Core Research for Evolutional Science and Technology of Japan Science and Technology Corporation (CREST-JST) Kawaguchi Saitama 332-0012 Japan

We investigated the behavior of the spin-triplet superconductor Sr2RuO4 ( Tc≈1.5K) under the magnetic fields parallel to the quasi-two-dimensional plane. The upper critical field Hc2 exhibits a clear fourfold anisotropy of about 3% at 0.35 K. Furthermore, we detected an additional transition feature below Hc2 in both the ac susceptibility and the specific heat. These second-transition features as well as the pronounced in-plane Hc2 anisotropy disappear above 0.8 K or under intentional field misalignment of less than 1°. Most of these characteristics are consistent with the predicted emergence of the second superconducting phase with a line-node gap.

关键词： .ac susceptibility in-plane Hc field misalignment line-node

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Femtosecond optical precursors in exciton resonant region

Femtosecond optical precursors in exciton resonant region

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Nonlinear Optics: Materials, Fundamentals and Applications

作者： M. Sakai H. Kunugita K. Ema Department of Physics Sophia University Chiyoda Tokyo Japan Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Japan

We performed propagation experiments of 150-fs optical pulses at the exciton resonance in CuCl. We observed several types of optical precursors corresponding to the Sommerfeld, the Brillouin, and the exciton precursors.

ISBN: (纸本)1557526451

关键词： Ultrafast optics Excitons Resonance Optical pulses Optical propagation Optical solitons Optical pulse shaping Frequency Pulse measurements Optical devices

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Transient nondegenerate four-wave mixing signal induced by exciton-exciton interactions in a self-organized quantum-well material

Transient nondegenerate four-wave mixing signal induced by e...

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Nonlinear Optics: Materials, Fundamentals and Applications

作者： J. Ishi Y. Kato H. Kunugita K. Ema T. Ban T. Kondo Department of Physics Sophia University Chiyoda Tokyo Japan Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Japan Department of Material Science University of Tokyo Bunkyo Tokyo Japan

ISBN: (纸本)1557526451

Polarization-dependent nondegenerate four-wave-mixing signal on a self-organized quantum-well material is measured and analyzed with seven-level density matrix description accounting for phase-space filling, excitation-induced dephasing and biexciton formation effects. It reveals these exciton-exciton interactions significantly influence polarization dependence.

关键词： Four-wave mixing Optical films Nonlinear optics Optical mixing Optical network units Optical filters Materials science and technology Optical polarization Excitons Optical pulses

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Self-Consistent Density Functional Calculation of Field Emission Currents from Metals

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Physical Review Letters 2000年第8期85卷 1750-1750页

作者： Y. Gohda Y. Nakamura K. Watanabe S. Watanabe Department of Materials Science The 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 Japan Department of Physics Science University of Tokyo 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan

We have developed a fully self-consistent method which is suitable to examine field emission currents, on the basis of the density functional theory. In our method, the nearby counterelectrode is not necessary. By using this method, we have investigated field emission currents from a biased metallic surface represented by the jellium model. We have found that the energy barrier between the jellium and vacuum becomes lower than the Fermi energy under strong electric fields (e.g., 10 V/nm for rs=4 bohr). In this situation, the slope of the Fowler-Nordheim plot becomes flatter than that under a weaker field.

关键词： Field emission cathodes

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Generation of coherent phonon oscillations in PbI/sub 2/ thin films

Generation of coherent phonon oscillations in PbI/sub 2/ thi...

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Nonlinear Optics: Materials, Fundamentals and Applications

作者： Y. Hirobe N. Ogawa H. Kunigita K. Ema T. Ban T. Kondo Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Japan Department of Physics Sophia University Chiyoda Tokyo Japan Jochi Daigaku Chiyoda-ku Tokyo JP Department of Mureriul Science University of Tokyo Bunkyo Tokyo Japan

We performed pump-probe transient absorption measurements around the exciton resonance in PbI/sub 2/ thin films. Coherent phonon oscillations corresponding to A/sub 1/ lattice mode were clearly observed at the excitat... 详细信息

关键词： Phonons Transistors Optical films Ultrafast optics Resonance Optical pulses Excitons Optical pumping Optical materials Semiconductor materials

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Ground-State Properties of a Rotating Bose-Einstein Condensate with Attractive Interaction

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Physical Review Letters 1999年第8期83卷 1489-1489页

作者： Masahito Ueda Anthony J. Leggett Department of Physical Electronics Hiroshima University Higashi-Hiroshima 739-8527 Japan and Core Research for Evolutional Science and Technology (CREST) JST Saitama 332-0012 Japan Department of Physics University of Illinois at Urbana-Champaign Urbana Illinois 61801-3080

The ground state of a rotating Bose-Einstein condensate with attractive interaction in a quasi-one-dimensional torus is studied in terms of the ratio γ of the mean-field interaction energy per particle to the single-particle energy-level spacing. The plateaus of quantized circulation are found to appear if and only if γ<1 with the lengths of the plateaus reduced due to hybridization of the condensate over different angular-momentum states.

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