スピン・電荷・軌道系の基礎理論

2002 Fiscal Year Annual Research Report

• Project/Area Number: 12046218
• Research Institution: The University of Tokyo
• Principal Investigator: 永長 直人 東京大学, 大学院・工学系研究科, 教授 (60164406)
• Co-Investigator(Kenkyū-buntansha): 宮下 精二 東京大学, 大学院・工学系研究科, 教授 (10143372) ; 小形 正男 東京大学, 大学院・理学系研究科, 助教授 (60185501) ; 福山 秀敏 東京大学, 物性研究所, 所長(研究職) (10004441) ; 今田 正俊 東京大学, 物性研究所, 教授 (70143542)
• Keywords: スピン / 電荷 / 起動 / 遷移金属酸化物 / 高温超伝導 / 磁性体 / 量子臨界現象 / トポロジー

Research Abstract

強相関電子系におけるスピン・軌道・電荷の自由度が織り成す多彩な現象を、量子モンテカルロ法、大規模行列厳密対角化等の数値的手法と、場の理論等の解析的手法の双方から調べた。具体的な成果は以下のとおりである。
(1)電荷秩序に関して、(i)ウィグナー結晶と電荷秩序の関係を明らかにした。(ii)マグネタイトにおける金属絶縁体転移の「電荷秩序」を伴わない全く新しいメカニズムを提唱した。(iii)分子性結晶における電荷秩序に関する系統的な研究をさらに展開した。
(2)軌道とスピンに関連した現象として、(i)ペロブスカイトチタン酸化物における多様な相の発生メカニズムを解明した。(ii)スピンー軌道相互作用が磁性体中の電子状態に、非自明な位相幾何学的構造をもたらすことを見出し、その結果として生じる異常ホール効果や超伝導に対する影響などを明らかにした。(iii)量子スピン系の熱伝導現象、ESRなどの理論を発展させた。
(3)高温超伝導体と関連物質に関して、(i)t-Jモデルにおける、反強磁性と超伝導状態の共存、ストライプ状態、磁束状態を調べ実験をよく説明することを示した。(ii)t-Jモデルに対して、新しいタイプの変分波動関数を提唱した。(iii)モット絶縁体に見出された、新しいタイプの非磁性絶縁相の本質を解明した。

Research Products

• [Publications] T.Mizusaki, M.Imada: "Extrapolation Method for Shell Model Calculations"Phvs.Rev.C. 65. 064319-064322 (2002)
• [Publications] A.Himeda, T.Kato, M.Ogata: "Stripe States with Spacially Oscillating d-Wave Superconductivity in the Two-Dimensional t-t'-J Model"Phys.Rev.Lett.. 88. 117001-1-117001-4 (2002)
• [Publications] Y.Noda, M.Imada: "Quantum Phase Transitions to Charge Order and Wigner Crystal Under Interplay of Lattice Commensurability and Long-Range Coulomb Interaction"Phys.Rev.Lett.. 89. 176803-176806 (2002)
• [Publications] A.Ogasawara, S.Miyashita: "Direct Numerical Analysis of ESR Line Shape In Low Dimensional Spin Systems"Mol.Cryst.Liq.Cryst.. 376. 321-326 (2002)
• [Publications] S.Miyashita, M.Nishno, K.Saito: "Quantum Dynamics and Response In Nanoscale Spin Systems"Mol.Cryst.Liq.Cryst.. 376. 327-334 (2002)
• [Publications] H.De Raedt, K.Michielsen, A.hams, S.Miyashita, K.Saito: "Quantum spin dynamics as a model for quantum computer operation"Eur.Phvs.J.B. 27. 15-28 (2002)
• [Publications] S.Miyashita, K.Saito, H.Nakano, M.Nishno: "Quantum Mechanical Dynamics in Mocroscopic Structures"Mol.Cryst.Liq.Cryst.. 379. 475-482 (2002)
• [Publications] H.Fukuyama, T.Sasaki, K.Yokoyama, Y.Ishikawa: "Orbital Magnetism in Confirmed Two-Dimensional System"J.Low Temper.Phys.. 126・3/4. 1067-1080 (2002)
• [Publications] Murakami S, Shindou R, Nagaosa N, et al.: "Lattice distortion and ferromagnetism in C_a B6"J.Phys.Chem.Sol.. 63・6-8. 1285-1287 (2002)
• [Publications] M.Ogata: "Spin Triplet Superconductivity in Sr_2 RuO_4 : Anisotropic Antiferromagnetis Spin-Fluctuation"J.Phys.Chem.Sol.. 63. 1329-1332 (2002)
• [Publications] T.Koretsune, M.Ogata: "The ground state energy and entropy of the two-dimensional t-J model"J.Phys.Chem.Sol.. 63. 1419-1422 (2002)
• [Publications] A.Himeda, M.Ogata: "The effect of the negative t' term on the stripe formation in the two-dimensional t-J model"J.Phys.Chem.Solid. 63. 1423-1426 (2002)
• [Publications] C, Hotta, H.Fukuyama: "Ferromagnetism in CaB6"J.Phys.Chem.Sol.. 63・6-8. 1505-1509 (2002)
• [Publications] H.Nakano, S.Miyashita: "Magnetization process of iron cluster with ring structure"J.Phys.Chem.Sol.. 63・6-8. 1519-1521 (2002)
• [Publications] Y.Saiga, Y., M.Imada: "Competition between Spin Exchange and Correlated Hopping"J.Phys.Chem.Sol.. 63・6-8. 1531-1535 (2002)
• [Publications] A.S.Mishchenko, N.Nagaosa: "Interplay of magnetic frustrations and lattice instability"J.Phys.Chem.Sol.. 63・6-8. 1603-1606 (2002)
• [Publications] T.Koretsune, M.Ogata: "Resonating-Valence-Bond States and Ferromagnetic Correlations in the Doped Triangular Mott Insulator"Phys.Rev.Lett.. 89. 116401-1-116401-4 (2002)
• [Publications] M.Onoda, N.Nagaosa: "Topological nature of anomalous Hall effect in ferromagnets"J.Phys.Soc.Jpn.. 71・1. 19-22 (2002)
• [Publications] S.Murakami, R.Shindou, N.Nagaosa, A.S.Mishchenko: "Lattice Distortion and Ferromagnetism in Ca_<1-x>La_xB_6"J.Phys.Soc.Jpn.. 71 Suppl.. 309-310 (2002)
• [Publications] M.Saito, M.Ogata: "Midgap States in Disordered Spin-Peierls Systems"J.Phys.Soc.Jpn.. 71. 721-724 (2002)
• [Publications] T.Sasaki, H.Fukuyama: "Electrical Conductance under Periodic Magnetic Field"J.Phys.Soc.Jpn.. 71・4. 1108-1117 (2002)
• [Publications] M.Mochizuki: "Spin and Orbital States and Their Phase Transitions of the Perovskite-Type Ti Oxides : Weak Coupling Approach"J.Phys.Soc.Jpn.. 71. 2039-2047 (2002)
• [Publications] H.Morita, S.Watanabe, M.Imada: "Nonmagnetic Insulating States near the Mott Transitions on Lattices with Geometrical Frustration and Implications for κ-(ET)2Cu2(CN)3"J.Phys.Soc.Jpn.. 71. 2109-2112 (2002)
• [Publications] M.Udagawa, M.Ogata, Z.Hiroi: "Exact Results of Ground-state Entropy for Ising Pyrochlore Magnets Under a Magnetic Field along [111] Axis"J.Phys.Soc.Jpn.. 71. 2365-2368 (2002)
• [Publications] M.Machida, K.Saito, S.Miyashita: "Frequency Dependence of Quantum Localization in a Periodically Driven System"J.Phys.Soc.Jpn.. 71. 2427-2433 (2002)
• [Publications] Keiji Saito, Seiji Miyashita: "Enhancement of the Thermal Conductivity in Gapped Quantum Spin Chains"J.Phys.Soc.Jpn.. 71. 2485-2488 (2002)
• [Publications] Hiroki Nakano, Seiji Miyashita: "Alternating Antisymmetric Interaction in Nanoscale Iron Ring"J.Phys.Soc.Jpn.. 71. 2580-2581 (2002)
• [Publications] H.Ohta, K.Kirita, T.Kunimoto, S.Okubo, Y.Hosokoshi, K.Katoh, K.Inoue, A.Ogasahara, S.Miyashita: "Low Dimensionality Observed by ESR Measurements in S=1/2 Spin Ladder Substance BIP-TENO (3,3', 5,5'-tetrakis (N-tert-butylaminoxyl) biphenyl)"J.Phys.Soc.Jpn.. 71. 2640-2643 (2002)
• [Publications] H.Tsuchiura, S.Uno, Y.Tanaka, M.Ogata, J.Inoue, S.Kashiwaya: "Vortex tunneling spectra of high-T_c superconductors based on the t-J model"Physica C. 367. 20-23 (2002)
• [Publications] Z.-X.Shen, A.Lanzara, S.Ishihara, N.Nagaosa: "Role of electron-phonon interaction in the strongly correlated cuprates superconductors"Phil.Mag.B. 82・13. 1349-1368 (2002)
• [Publications] H.Seo, M.Ogata, H.Fukuyama: "Aspects of the Verwey Transition in Magnetite"Phys.Rev.B. 65・8. 085107-1-085107-7 (2002)
• [Publications] C.Hotta, H.Fukuyama: "Possible Ferromagnetism in Divalent Boride Systems"Phys.Rev.B. 65・18. 184421-1-184421-5 (2002)
• [Publications] M.Onoda, N.Nagaosa: "Particle-hole symmetry and transport properties of the flux state in underdoped cuprates"Phys.Rev.B. 65. 214502-1-214502-12 (2002)
• [Publications] S.Murakami, R.Shindou, N.Nagaosa, A.S.Mishchenko: "Theory of excitonic states in C_aB6"Phys.Rev.B. 66. 184405 (2002)
• [Publications] A.S.Mishchenko, N.Prokofiev, A.Sakamoto, N.Nagaosa: "Self-trapping in Rashba-Pekar model"Phys.Rev.B. 66. 020301 (2002)
• [Publications] N.Todoroki, Y.Ueno, S.Miyashita: "Order phase and phase transitions in the three-dimensional generalized six-state clock model"Phys.Rev.B. 66. 214405(8) (2002)
• [Publications] H.Seo, M.Ogata, H.Fukuyama: "Orbital Ordering and Bond Dimerization in Magnetite Fe3O4"Physica B. 312. 691-693 (2002)
• [Publications] M.Ogata, A.Himeda: "Superconductivity and Antiferromagnetism in an Extended Gutzwiller Approximation for t-J Model : Effect of Double-Occupancy Exclusion"J.Phys.Soc.Jpn.. 72. 374-391 (2002)
• [Publications] Luty T, Cailleau H, Koshihara S, E.Collet, N.Nagaosa, Y.Tokura et al.: "Static and dynamic order of cooperative multi-electron transfer"Europhys.Lett.. 59・4. 619-625 (2002)
• [Publications] H.Onishi, S.Miyashita: "Quantum Narrowing Effect in a Spin-Peierls System with Quantum Lattice Fluctuation"J.Phys.Soc.Jpn.. 72. 392-398 (2003)
• [Publications] I.Chiorescu, W.Wernsdorfer, A.Mller, S.Miyashita, B.Barbara: "Adiabatic Landau-Zener-Stckelberg transition with or without dissipation in the low-spin molecular system V15"Phys.Rev.B. 67. 020402(4) (2003)
• [Publications] Zhong Fang, Nagaosa N, Kiyoyuki Terakura: "Anisotropic optical conductivities due to spin and orbital ordering in LaVO3 and YVO3 First-principles studies"Phys.Rev.B. 67. 035101 (2003)
• [Publications] S.Murakami, N.Nagaosa: "Berry Phase in Magnetic Superconductors"Phys.Rev.Lett.. 90. 057002 (2003)
• [Publications] T.K.Lee, Chang-Ming Ho, N.Nagaosa: "Theory for Slightly Doped Antiferromagnetic Mott Insulators"Phys.Rev.Lett.. 90. 067001 (2003)
• [Publications] M.Nishino, S.Miyashita, K.Boukheddaden: "Effective interaction range in the spin crossover"J.Chem.Phys.. (in press). (4) (2003)
• [Publications] A.Ogasahara, S.Miyashita: "ESR Line Shape in Strongly Interacting Spin Systems"J.Phys.Soc.Jpn.. 72(in press). (6) (2003)
• [Publications] Y.Yanase, M.Ogata: "Microscopic Identification of the D-vector in Triplet Superconductor Sr_2RuO_4"J.Phys.Soc.Japan. 72. (2003)
• [Publications] S.Miyashita, K.Saito: "Real time scale simulation for quantum process in dissipative environments"Physica B. (in press). (2) (2003)
• [Publications] S.Onoda, S., M.Imada: "Operator Projection Theory for Electron Differentiation in Underdoped Cuprate Superconductors"J.Phys.Chem.Solids. (in press).
• [Publications] M.Matsuura, Y.Endoh, H.Hiraka, K.Yamada, A.S.Mishchenko, N.Nagaosa, I.V.Solovyev: "Classical and quantum spin dynamics in face-centered-cubic antiferromagnet NiSsub2 with frustration"Phys.Rev.B. (accepted). (2003)
• [Publications] Ryo Maezono, Naoto Nagaosa: "Jahn-Teller effect and electron correlation in manganites"Phys.Rev.B. (accepted). (2003)
• [Publications] Yukitoshi Motome, Hitoshi Seo, Zhong Fang, Naoto Nagaosa: "One-dimensional confinement and enhanced Jahn-Teller instability in LaVO3"Physical Review Letters. (accepted). (2003)
• [Publications] 永長 直人: "物質の中の宇宙論"岩波書店. 97 (2002)
• [Publications] 福山秀敏, 小形正男: "物理数学I"朝倉書店. (2003)
• [Publications] 妹尾仁嗣, 鹿野田一司, 福山秀敏: "解説「分子性結晶における電荷秩序"日本物理学会誌(執筆中).