| Co-Investigator(Kenkyū-buntansha) |
SUGA Shigemasa Osaka University, Graduate School of Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (40107438)
ONUKI Yoshichika Osaka University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (40118659)
KITAOKA Yoshio Osaka University, Graduate School of Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (70110707)
SHIMIZU Katsuya Osaka University, Graduate School of Engineering Science, Lecturer, 大学院・基礎工学研究科, 講師 (70283736)
ITOH Tadashi Osaka University, Graduate School of Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (60004503)
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| Research Abstract |
Research was performed in the following three subject : [1] Properties of strongly correlated electrons, [2] Correlated electron phase in confined systems, and [3] Electron phases under ultra-high pressures.
[1] Properties of strongly correlated electrons (Miyake, Kitaoka, OnuK, Suga)
New mechanism of superconductivity of due to critical valence fluctuations is found, new types of mechanism are proposed for superconductivity in Uge_2, Upd_2Al_3, PrOs_4Sb_<12>, (TMTSF)_2PF_6, and the phase of CeCu_2Si_2 and CeRhIn_5 coexisting with the antiferromagnetism (Miyake). By means of NMR/NQR techniques, spin-triplet superconductivity in heavy-fermion (Upt_3 and Uni_2Al_3) and rutenate oxide (Sr_2RuO_4) systems, microscopic coexisting phase of antiferromagnetism and superconductivity in heavy-fermion compounds under pressure, a nano-scale coexistence of antiferromagnetism and superconductivity in multilayered high-temperature superconductors, have been discovered (Kitaoka). High-quality single cry
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stals of cerium and uranium compounds over fifty in number have been grown, and their magnetic and Fermi-surface properties have been clarified (Onuki). High resolution (energy and wave vector) soft X-ray photoemision spectroscopy of rare earth and transition metal compounds have been succeeded for the first time in the world, and many controversies are solved and going to be solved by this break through of the bulk sensitive technique (Suga).
[2] Correlated electron phase in confined systems (Itoh, Cho, Hiyamizu, One, Ogawa, Nozue)
Both in the strong and weak confinement regimes, the dependencies of exciton energy and life time upon the number of excitons in a single nano-structure were studied and the evidence of electron correlation in confined systems and its relation with optical nonlinearities were found. The concept of photonic de Broglie wavelength in correlated photon system was verified (Itoh). A new theoretical scheme of "microscopic nonlocal optical response of matter" has been highly developed and applied to various linear and nonlinear processes in nanostructures and related systems (Cho). Room temperature oscillation of MBE-grown In_<0.1>Ga$_<0.9>As/(GaAs)_6(AlAs)_1 quantum wire (QWR) lasers on (775)B GaAs substrates with an emission wavelength range of 0.85μ was demonstrated, and extremely uniform (221)A In_<0.22>Ga_<0.78>As/GaAs quantum wires were fabricated (Hiyamizu). For the purpose of creating novel effects based on spin-polarized current, magnetoresistive control of a manganite by spin-polarized current, spin injection from ferromagnet into superconductor, and current-induced domain wall motion were studied experimentally (Ono). "Photoinduced Phase Transition" was studied theoretically to clarify the phase-separation dynamics, formation of classical and quantum orders, and quantum many-body effects on linear/nonlinear optical responses in photoexcited nonequilibrium states of many-electron systems (Ogawa). The spatial distribution and the electron transport phenomena of edge state in integer and fractional quantum Hall system are found to be strongly affected by the confinement potential, and an orbital degeneracy of alkali metal clusters in zeolite is found to play an important role for its ferromagnetism (Nozue).
[3] Electron phases under ultra-high pressures (Suzuki, Nasu, Shimizu, Kobayashi)
It has been shown for the first time that the pressure-induced insulator-metal transition in solid oxygen would be realized by band overlapping (Suzuki). High pressure ^<57>Fe Mossbauer measurements have been performed, clarifying the magnetic property of ε-Fe which is a high-pressure phase of metallic Fe (Nasu). Techniques of generating very low-temperature and ultra high-pressure and measuring physical properties have been developed, and superconductivity under pressure was discovered in simple systems, such as oxygen, iron, lithium and organic molecular crystals, an ionic crystal, etc. (Shimizu). By means of newly developed high-pressure cell, the pressure-induced magnetic-nonmagnetic transition, superconductivity and charge-ordering have been found in the U- and Ce-based heavy electron compounds, particularly in the ferromagnetic superconductor Uge_2, the bulk nature of the superconductivity was established by the heat capacity measurements (Kobayashi). Less
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