超伝導発現機構の解明(超伝導理論班)

1990 Fiscal Year Annual Research Report

• Project/Area Number: 02213103
• Research Institution: The University of Tokyo
• Principal Investigator: 福山 秀敏 東京大学, 物性研究所, 教授 (10004441)
• Co-Investigator(Kenkyū-buntansha): 前川 禎通 名古屋大学, 工学部, 教授 (60005973) ; 斯波 弘行 東京工業大学, 理学部, 教授 (30028196) ; 小谷 章雄 東京大学, 物性研究所, 教授 (90029504) ; 黒田 義浩 名古屋大学, 理学部, 教授 (60013504) ; 立木 昌 東北大学, 金属材料研究所, 教授 (20028111)
• Keywords: 銅酸化物 / 強相関電子系 / バンド理論 / クラスタ-計算 / ハバ-ド模型 / モット絶縁体 / tーJモデル

Research Abstract

銅酸化物高温超伝導体は強い電子間相関に起因する電荷移動型絶縁体にキャリアをド-プした状態で発現しており、強相関という粒子数で表現される粒子性と金属的に電子が動く波動性という量子力学的双対性をいかに理論的に表現するという極めて根源的な問題に各分担者は挑戦しており、本年度も多岐にわたる研究がなされた。まず、ド-ピングに伴って、電荷移動ギャップに状態が出現するという実験結果に刺激され、dーpモデルを出発点に強相関系という観点から、黒田、立木らによって追求され、糸口が見つけられた。また、大局的な電子状態が従来のバンド理論の枠組みの中で、寺倉、糟谷、柳瀬、望月らによって研究され、とくに電子型の場合キャリアの波動関数について、新しい知見が得られた。また、系が持つイオン結晶的な性格に着目して、面内と頂点にある酸素のマ-デルング・エネルギ-の差と電子状態とくに臨界温度との相関が前川、近藤らによってなされた。このようなエネルギ-スケ-ルの大きい領域で見られる強相関系の特徴は、光電子スペクトルによって観測されるが、これらについての詳細な理論的研究が小谷らによってなされ、ド-ピングに伴って生じたキャリアの性格が論じられた。また、高エネルギ-領域と低エネルギ-領域の関連は有効ハミルトニアンの立場からも松川らによって研究された。低エネルギ-領域、即ち、輸送現象等の電気的及び各磁気緩和等の磁気的性質についても、いろいろの立場からの研究がある。まず、フェルミ流体論的一般論をもとに諸性質の統一的理解を山田、芳田らが提案、スピンのゆらぎに対する自己無憧着理論に基づく研究が守谷らによって、更に強相関ゲ-ジ場の観点から永長、福山らによって追求され、それぞれ実験と比較できる具体的予言が可能になった。この領域の進展は著しい。この他tーJモデルにおける数値計算及び1、2次元電子系における多体問題に対する寄与も大きい。

Research Products

• [Publications] O.Narikiyo: "Anyons in Extended tーJ Model" Journal of The Physical Society of Japan. 59. 2443-2456 (1990)
• [Publications] H.Fukuyama: "Perturbation Theory and Singularities in TwoーDimensional Hubbard Model at Low Electron Density" Journal of The Physical Society of Japan. 60. 372-375 (1991)
• [Publications] S.Nakajima: "The HolonーSpinon Operator Formalism" Journal of The Physical Society of Japan. 60. (1991)
• [Publications] S.Nakajima: "Toward Simple Theory of HighーT_c Superconductivity" Journal of Advanced Science. 3. (1991)
• [Publications] J.Kondo: "The Madelung Energy in CopperーOxideーBased Ceramics" Journal of The Physical Society of Japan. 57. 4334-4342 (1988)
• [Publications] J.Kondo: "Carrier Distribution in Oxide Superconductors" Journal of The Physical Society of Japan. 58. 2884-2895 (1989)
• [Publications] J.Kondo: "Oxygen Ordering in YBCO" Journal of The Physical Society of Japan. 59. 819-821 (1990)
• [Publications] Y.Ono: "Critical Study of Strongly Correlated Systems:A Unified Description of The Incoherent and Coherent Regimes" Physica C. 159. 878-888 (1989)
• [Publications] H.Jichu: "Electronic States in HighーT_c CopperーOxide SuperconductorsII" Journal of The Physical Society of Japan. 59. 2820-2830 (1990)
• [Publications] Y.Kuroda: "Superconductive State of CuーO Metals" Physical Review B. 42. 8619-8622 (1990)
• [Publications] N.Shirai: "ElectronーPhonon Interaction and Lattice Dynamics in BaPb_<1ーx>Bi_xO_3" Ferroelectrics. 96. 99-103 (1989)
• [Publications] M.Shirai: "Theoretical Study of Tunneling Spectra in Ba_xK_<1ーx>BiO_3" Solid State Communications. 73. 633-635 (1990)
• [Publications] M.Shirai: "ElectronーLattice Interaction and Superconductivity in BaPb_<1ーx>BiO_3 and Ba_xK_<1ーx>BiO_3" Journal of Phys.:Condensed Matter. 2. 3553-3566 (1990)
• [Publications] K.TaKegahara: "Electronic Band Structure of Paramagnetic and Antiferromagnetic La_2NiO_4" Solid State Communications. 70. 641-645 (1989)
• [Publications] K.Takegahara: "Nature of Doped Electrons in Nd_<2ーx>Ce_xCuO_4:Electronic Band Structures of Nd_2CuO_4 Type M_2CuO_4(M=La,Ce and Th)" Journal of The Physical Society of Japan. 59. 2098-2109 (1990)
• [Publications] S.Ishihara: "Effective Hamiltonian of Oxide Superconductors and a Narrow Band near the Fermi Level" Physical Review B. 42. 10041-10051 (1990)
• [Publications] M.Tachiki: "Electronic state of superconducting copper oxides" Proc.of the Yamada Conference XXV on Magnetic Phase Transition.
• [Publications] M.Tachiki: "Theory of Superconductivity in Multilayer Systems" Proc.19th Int.Conf.on Low Temperature Physics.
• [Publications] T.Thoyama: "Effects of CarrierーDoping on Optical Conductivity in High T_c Cu Oxides" Journal of The Physical Society of Japan. 60. 53-56 (1991)
• [Publications] J.Inoue: "Theory of the Giant Magnetoresistance in Metallic Superlattices" Journal of The Physical Society of Japan. 60. 376-379 (1991)
• [Publications] T.Tsuneto: "Fluctuation Effects in High T_c Superconductors in Strong Fields" Physica C. 162ー164. 1693-1696 (1989)
• [Publications] T.Tsuneto: "Renormalized Superconducting Fluctuations in Magnetic FieldーExtrapolation to Lower Temperatureー" Journal of The Physical Society of Japan. 59. 1397-1409 (1990)
• [Publications] T.Tsuneto: "Massless Mode of Abrikosov Flux Lattice" Journal of The Physical Society of Japan. 59. 1740-1752 (1990)
• [Publications] S.Fujimoto: "Anomalous Damping of Quasiparticles in TwoーDimensional Fermi Systems" Journal of The Physical Society of Japan. 59. 2316-2319 (1990)
• [Publications] M.Ozaki: "Symmetries of the Solution of the tーJ Model" Prog.Theor.Phys.84. 1053-1073 (1990)
• [Publications] H.Kohno: "Analisis of Normal State Properties of HighーT_c Superconductors on the Basis of Fermi Liguid Theory" Prog.Thor.Phys.85. 13-29 (1991)
• [Publications] Y.Takahashi: "Hole Propagation in a 2D Quantum Spinー1/2 Antiferromagnet.II.Effect of Finite J Correction" Journal of The Physical Society of Japan. 59. 2931-2940 (1990)
• [Publications] T.Moriya: "Antiferromagnetic Spin Fluctuations and Superconductivity in TwoーDimensional MetalsーA possible model for high T_c oxides" Journal of The Physical Society of Japan. 59. 2905-2915 (1990)
• [Publications] T.Moriya: "Anomalous optical Conductivity in the Normal State of High T_c Oxides" Journal of The Physical Society of Japan.
• [Publications] M.Ogata: "Bethe Ansatz Wave Function,Momentum Distribution and Spin Correlation in OneーDimensional Strongly Correlated Hubbard Model" Physical Review B. 41. 2326-2338 (1990)
• [Publications] M.Ogata: "Magnetic Field Effects on Correlation Functions in OneーDimensional Strongly Correlated Hubbard Model" Physical Review B. 43. (1991)
• [Publications] 斯波 弘行: "酸化物高温超伝導ーメカニズム解明はどこまで進んでいるかー" 科学. 60. 258-265 (1990)
• [Publications] K.T.Park: "Implications of BandーStructure Calculations for HighーT_c Related Oxides" Journal of The Physical Society of Japan. 57. 3445-3456 (1988)
• [Publications] T.Oguchi: "Electronic band structure of YBa_2Cu_4O_8" Physica C. 172. 277-281 (1990)
• [Publications] Y.Ishii: "Localized orbitals and singleーelctron spectrum in selfinteractionーcorrected densityーfunctional theory" Physical Review B. 42. 10924-10932 (1990)
• [Publications] Y.Hatsugai: "Paring of fermions Coupled with Spinー1/2 Heisenberg SystemーExact Diagnalization Study of Mechanism of HighーT_c Superconductivity" Journal of The Physical Society of Japan. 58. 1347-1371 (1989)
• [Publications] M.Imada: "Numerical Studies on the Hubbard Model and the tーJ Model in Oneーand TwoーDimensions" Journal of The Physical Society of Japan. 58. 3752-3780 (1989)
• [Publications] D.Yoshioka: "Superconductivity of the tーt'J Model" Journal of The Physical Society of Japan. 58. 4276-4279 (1989)
• [Publications] D.Yoshioka: "Displacement of Apical Oxygen of the Oxide Superconductors below T_c" Journal of The Physical Society of Japan. 59. 2627-2630 (1990)
• [Publications] D.Yoshioka: "Boson Mean Field Theory of the Triangular Lattice Heisenberg Model" Journal of The Physical Society of Japan. 60. 616-626 (1991)
• [Publications] A.Kotani: "Theory of Cu2p Core XPS,XES and XAS in HighーT_c Superconducting Materials" Physica Scripta. 41. 569-573 (1990)
• [Publications] K.Okada: "Role of Cu4s Band in Cu 2pーXPS of Nd_<2ーx>Ce_xCuo_4" Journal of The Physical Society of Japan. 59. 2639-2642 (1990)
• [Publications] K.Okada: "Polarization Dependence of CoreーLevel Xーray Photoemission Spectra in Anisotropic Solids" Solid State Communications. 76. 1277-1279 (1990)
• [Publications] K.Ohara: "A Modified SpinーWave Theory of the SquareーLattice Antiferromagnets I" Journal of The Physical Society of Japan. 58. 2521-2530 (1989)
• [Publications] K.Ohara: "A Modified SpinーWave Theory of the SquareーLattice Antiferromagnets II" Journal of the Physical Society of Japan. 59. 3341-3344 (1990)
• [Publications] K.Hanzawa: "The Electric Field Grandients from the OnーSite Holes at Cu and O Nuclei in YBa_2Cu_3O_7" Journal of The Physical Society of Japan. 59. 3345-3350 (1990)
• [Publications] M.Imada: "Proceedings of Yamada Conference XXIV on Strongly Coupled Plasma Physics" Elsevier Science Publishers, (1990)