モット転移近傍の異常金属相-銅酸化物の異常金属相と高温超伝導体-

1997 年度 実績報告書

• 研究課題/領域番号: 07237105
• 研究機関: 名古屋大学
• 研究代表者: 佐藤 正俊 名古屋大学, 大学院・理学研究科, 教授 (40092225)
• 研究分担者: 藤田 敏三 広島大学, 理学部, 教授 (20004369) ; 朝山 邦輔 大阪大学, 大学院・基礎工学部, 教授 (20029416) ; 内田 慎一 東北大学, 大学院・工学研究科, 教授 (10114399) ; 遠藤 康夫 東北大学, 大学院・理学研究科, 教授 (00013483) ; 伊土 政幸 北海道大学, 大学院・理学研究科, 教授 (90111145)
• キーワード: モット転移 / 異常金属相 / 高温超伝導 / スピンギャップ / 強相関電子系

研究概要

高温超伝導体の異常金属相は、モット絶縁相にドープされた正孔の濃度pと温度TのT-p平面において、T<T_0(p)(p≦P_0,T_0(p)=0)の限られた領域に存在する。これはHall係数や帯磁率の挙動からわかったことである。このp領域と超伝導の出現する領域との一致がこの相と超伝導相の密接な関係を端的に示すが、特にT_0以下の異常物性が超伝導相におけるものと同じ対称性をもった電子スピン-重項の形成、さらにはそれに伴った擬ギャップ形成によるものであることを示唆するいくつかの実験結果が発表されるに及んで、この相の概容が見えてきた。核磁気共鳴の実験結果から提出されていたいわゆる"スピンギャップ異常"の温度T_<SG>(T_c<T_<SG><T_OとT_Oの関係を含めたこの系の物性の解釈は次のようになる。電子の反強磁性的相関とスピン-重項相関が降温とともにT_O付近からともに成長する。さらにT_<SG>まで温度が降下するとスピン-重項相関が支配的となり"スピンギャップ異常"としてそれが顕在化するが、超伝導が現れるのは量子ゆらぎのためにT_<>まで温度が下がってからである。中性子散乱、核磁気共鳴、角度分解光電子分光、STM/STS等を手段にした、銅酸化物や他の関連物質系に対する本年度の綿密な研究は、上述のような擬ギャップ形成から超伝導出現に至る物理描像をより明快なものにするためのものであった。このような描像は高温超伝導の発現メカニズムが磁気的相互作用によるもので、特にCuスピン間に働く大きな交換相互作用Jがその高いT_cの実現に極めて重要であることをさし示している。
その他スピンラダー系超伝導体のスピンギャップ研究や電子ドープ系における超伝導対称性に関する研究等において多くの知見が得られたが、そればかりではなく1次元系のスピン電荷分離現象の直接観測や、遷移金属化合物の金属-絶縁体転移に関する研究等、強相関電子系に対する広い視野からの多彩な研究がなされ、この分野の研究が方向づけられた。

研究成果

• [文献書誌] H.Sasaki: "Structural Studies on the Phase Transition of La_3Ni_2O_<6.92> at about 550K" J.Phys.Soc.Jpn.66. 1693-1697 (1997)
• [文献書誌] N.Yamada: "Polarization Analysis of X-Ray Absorption at the O ls Absorption Edge in PrBa:Cu:O_7:Unusurl Electronic Structure in CuO_2 Plane" Physica C. 282-287. 963-964 (1997)
• [文献書誌] H.Kamijo: "Electron and phonon Thermal Conducturty of High-Tc Systems from the Underdoped Insulating to the Nonsupercenducting Metallic Phase" J.Phys.Soc.Jpn.66. 2466-2472 (1997)
• [文献書誌] Y.Kobayashi: "^<51>V-NMR Study of the Misfit Layer Compounds La_<1.17-x>Sr_xVS_<3.17>" J.Phys.Soc.Jpn. 66. 4027-4030 (1997)
• [文献書誌] Y.Yasui: "Phase Diagram and Pressure Effects on Transport Properties of BaCo_<1-x>Ni_xS_2" J.Phys.Soc.Jpn.66. 3194-3201 (1997)
• [文献書誌] S.Taniguchi: "ESR Studies on CaV_4O_9 and CaV_3O_7" J.Phys.Soc.Jpn.66. 3660-3664 (1997)
• [文献書誌] H.Sasaki: "Dynamical Magnetic Properties of BaCo_<1-x>Ni_xS_2 near the Mott Transitions Induced by Pressure and Carrier-Number Control" J.Phys.Soc.Jpn.66. 3975-3980 (1997)
• [文献書誌] E.Z.Kurmaev: "Excitation Energy Dependence of SL_2,3 X-Ray Fluoresent Emission of BaNiS_2 near _<2p> Threshold" Phys.Lett.A.235. 191-194 (1997)
• [文献書誌] K.Kodama: "Spin Gap Behavior of CuNb_2O_6" J.Phys.Soc.Jpn.67. 57-60 (1998)
• [文献書誌] M.Sato: "Metal-Insulator Transitions of BaCo_<1-x>Ni_xS_2 Induced by Pressure and Camer Number Control" The Review of High Pressure Science and Technology. 7(in press). (1998)
• [文献書誌] H.Harashina: "Magnetic Excitation of BaCoS_2 near the Mott Fransitions Induced by Pressure and Carrier-Number Control" The Review of High Pressure Science and Technology. 7(in press). (1998)
• [文献書誌] Y.Yasui: "Pressure Effects on the Mott Metal-Insulator Transitions in BaCo_<1-x>Ni_xS_2" The Review of High Pressure Science and Technology. 7(in press). (1998)
• [文献書誌] A.Fujimori: "Chemical Potential Shifts in Correlated Electron Systems Studied by Photoemission Spectroscopy" J.Electron Spectroscopy and Related Phenomena. (in press).
• [文献書誌] M.Sato: "The Anomalous Metallic Phase and High-T_c Superconductionty of Cu Oxides" Studies of High Temperature Superconductors ed.by A.V..Narlikar. 19. 213-243 (1996)
• [文献書誌] 佐藤 正俊: "高温超伝導十年 電子物性・超伝導機構 実験の立場から" 日本物理学会誌. 52. 174-176 (1997)
• [文献書誌] 佐藤 正俊: "高温超伝導:実験はどこまで追ったか" 高温超伝導とフラーレンの科学(第11回大学と科学公開シンポジウム. 31-46 (1997)
• [文献書誌] M.Oda: "Strong pairing interactions in the underdoped region of Bi_2Sr_2CaCu_2O_<8+δ>" Physica C. 281. 135-142 (1997)
• [文献書誌] M.Oda: "STM/STS Studies for doping effects on the symmetry and magnitude of superconducting gap in Bi_2Sr_2CaCu_2O_<8+δ>" Physica C. 282-287. 1499-1500 (1997)
• [文献書誌] C.Manabe: "Atomic Images and Tunneling Spectra on Bi_2Sr_2CaCu_2O_<8+δ> Cleaved Surface by STM" Journal of the Physical Society of Japan. 66. 1776-1784 (1997)
• [文献書誌] M.Oda: "Strong Pairing interaction and pseudogap behavior in underdoped Bi_2Sr_2CaCu_2O_<8+δ>" Journal of Physics and Chemistry of Solids. (in press).
• [文献書誌] N.Momono: "Dependence of superconducting gap on hole doping level in La_<2-x>Sr_xCuO_4" Journal of Physics and Chemistry of Solids. (in press).
• [文献書誌] H.Ding: "Evolution of the Fermi Surface with Carrier Concentration in Bi_2Sr_2CaCu_2O_<8+δ>" Phys.Rev.Lett.78. 2628-2631 (1997)
• [文献書誌] N.Nagasako: "Electronic Band Structure of SrCuO_2" J.Phys.Soc.Jpn.66. 1756-1761 (1997)
• [文献書誌] T.Yokoya: "Angle-Resolved Photoemission Spectroscopy of Non-Cuprato Two Dimensional Perovskite Superconductor Sr_2RuO_4" Physica B. 237-238. 377-379 (1997)
• [文献書誌] T.Takahashi: "Angle-Resolved.photoemission study of Sr_2RuO_4,an Extended van-Hove Singularity in Non-Cuprate Superconductor" Physica C. 282-287. 218-221 (1997)
• [文献書誌] T.Takeuchi: "ARPES Studies of Pb SubstitutedBi2201 Compounds" Physica C. 282-287. 999-1000 (1997)
• [文献書誌] T.Yokoya: "High-Resolution Angle-Resolved Photoemission Study of Sr_<14-x>Ca_xCu_<24>O_<41>(x=0 and 6)" Physica C. 282-297. 997-998 (1997)
• [文献書誌] T.Takahashi: "Angle-Resolied Photoemission Study of Ladder Compound Sr_<14>Cu_<24>O_<41>" Phys.Rev.B. 56. 7870-7873 (1997)
• [文献書誌] O.Akaki: "Unconventional Spectral Changes Across the Metal-Insulator Transition in CeTiO_<3+δ>" Phys.Rev.B. 56. 12050-12053 (1997)
• [文献書誌] M.R.Norman: "Unusual Dispersion and Lineshape of the Superconducting state Spectra of Bi_2Sr_2CaCu_2O_<8+δ>" Phys.Rev.Lett.79. 3506-3509 (1997)
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• [文献書誌] A.Chainani: "Temperature Dependence of the Electronic Structure of the charge-Ordering Manganite Pr_<0.5>Sr_<0.5>MnO_3" Phys.Rev.B. (in press).
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• [文献書誌] M.Hiroi: "Unusual Antiferromagnetic State in Si-doped CuGeO_3 single Crystale Studied by Specific-Heat Measurements in Magnetic Fields" Phys.Rev.B. 55. R6125-R6128 (1997)
• [文献書誌] M.Sera: "Unusual Antiferromagnetic State in the Dimecuzed Phase in CuGe_<1-x>Si_xO_3 Studied by Lattice Distortion" Phys.Rev.B. 56. 14771-14775 (1997)
• [文献書誌] Y.Endoh: "Spin Fluctuations in Highly Corrclated Electrons Probed by Neutron Scattering" Hyperpine Interactions. 104. 23-28 (1997)
• [文献書誌] K.Nakajima: "Neutron Scattering Study of Oxygen Ordering and Magnetic Correlations in La_2NiO_<4.11> and La_2NiO_<4.125>" J.Phys.Soc.Jpn.66. 809-817 (1997)
• [文献書誌] J.A.Fernandez-Baca: "Effect of pressure on the Magnetic Phase Diagram of the Antiferromagnetic Spin Density Wave Alloy Cr-1.6% Si" J.Appl.Phys.81. (1997)
• [文献書誌] Y.Endoh: "Polarized Neutron Studies for Cr Excitations" J.Phys.Soc.Jpn.66. 1615-1617 (1997)
• [文献書誌] T.Fukuda: "Dynamical Susceptibility of the SDW State in Cr" Physica B. 237-238. 430-431 (1997)
• [文献書誌] H.Hiraka: "Spin Dynamics in a Metallic Ferromagnet CoS_2" Physica B. 237-238. 478-479 (1997)
• [文献書誌] T.Endoh: "Scaling of Spin-Wave Stiffness Constant to Curie Temperature in the Colossal Magnetoresistance Material La_<1-x>Sr_xMnO_3" J.Phys.Soc.Jpn.66. 2264-2267 (1997)
• [文献書誌] Y.Endoh: "Phase Separation,Staging and Spin Fluctuations in La_2CuO_<4+y>" Physica C. 282-287. 170-173 (1997)
• [文献書誌] K.Yamada: "Low Frequency Spin Fluctuations in the Superconducting La_<2-x>Sr_xCuO_4" Physica C. 282-287. 85-88 (1997)
• [文献書誌] K.Kojima: "Reduction of Ordered Moment and Neil Temperature of Quasi One Dimensional Antiferromagnet Sr_2CuO_3 and Ca_2CuO_3" Phys.Rev.Lett.78. 1787-1790 (1997)
• [文献書誌] B.O.Wells: "Structures and Incommensurate Spin Fluctuations in Oxygen-Doped La_2CuO_<4+y> High Temperature Superconductors" Science. 277. 1067- (1997)
• [文献書誌] K.Iwasa: "Thermoelectric Power of Delafossite-Derived Compounds,RCuO_<2+δ>(R=Y,La,Pr,Nd,Sm and Eu)" Phys.Rev.B. (in press).
• [文献書誌] E.Torikai: "Probing Interaction of Paramagnetic Electron with Conduction Electrons in High-Tc Superconductor LaSrCuO by μ-on Spin Relaxation" Hyperfine Interaction. 105. 175-179 (1997)
• [文献書誌] T.Suzuki: "Observation of Modulated-Magnetic Long-Range Order in La_<1.88>Sr_<0.12>CuO_4" Phys.Rev.B. (in press).
• [文献書誌] R.J.Birgeneau: "Structures and Incommensurate Spin Excitations in Excess Oxygen-Doped La_2CuO_<4+y>" Physica B. 237-238. 84-90 (1997)
• [文献書誌] K.Yamada: "Neutron Scattering Study of Low Energy Spin Fluctuations in La_<2-x>Sr_xCuO_4" J.Supercond. 10. 343-347 (1997)
• [文献書誌] K.Hirota: "Quasi-Elactic Incommensurate Peaks in La_<2-x>Sr_xCu_<1-y>ZnyO_<4-δ>" Proc.Int.Conf.on Neutron Scattering. (in press).
• [文献書誌] S.Wakimoto: "Two-Dimensional Antiferromagnetic Correlations in the Oxygen-Doped 2-1-4 Type Cuprates" Physica B. 237-238. 91-92 (1997)
• [文献書誌] M.Matsuda: "Surft Heavyion irradiation Effects on the Single Crystal La_<1.85>Sr_<0.15>CuO_4" Physica Scripta. 73. 340-342 (1997)
• [文献書誌] M.Fujita: "Study on Quantum Magnetic Excitation of CuGeO_3 Using Pulsed Ncutlon Scattering" Physica B. 237-238. 132-134 (1997)
• [文献書誌] M.Arai: "Dynamic Structure Factor of Non-Crystalline and Crystalline Systems as revealed by MARI,a Neutron Chopper Instrument" Advances in Colloid and Interface Science. 71-72. 209-232 (1997)
• [文献書誌] 新井 正敏: "パルス中性子散乱による物質の研究" Isotope News. 521. 2-7 (1997)
• [文献書誌] M.Arai: "High-Energy T-O-F Neutron Spectroscopy on Quantunr Spin Systems" Physica B. 237-238. 127-131 (1997)
• [文献書誌] A.Ino: "Chemical Potential Shift in Overdoped and Underdoped La_<2-x>Sr_2CuO_4" Phys.Rev.Lett.79. 2101-2104 (1997)
• [文献書誌] R.Henn: "Dynamics of the c-axis polarized infrared-active modes in La_<2-x>Sr_xCuO_4" Phys.Rev.B. 56. 6295-6301 (1997)
• [文献書誌] K.Takenaka: "In-plane thermal conduchvity and Lorenz number in YBa_2Cu_3O_<7-y>" Phys.Rev.B. 56. 5654-5661 (1997)
• [文献書誌] J.E.Ostenson: "Flux expulsion and reversible magnetization in the stripe phase Superconductor" Phys.Rev.B. 56. 2820-2823 (1997)
• [文献書誌] J.M.Harris: "Measurement of an Anisotropic Gap in Single Plane Bi_2Sr_<2-x>Ca_xCuO_<6+δ>" Phys.Rev.Lett.79. 143-146 (1997)
• [文献書誌] S.Uchida: "Optical conductivity studies of high-Tc Superconductors" Hyperfine Interactions. 105. 47-59 (1997)
• [文献書誌] T.Boske: "High-Resolution x-ray-photoemission study of Sr_2CuO_2Cl_2" Phys.Rev.B. 56. 3438-3446 (1997)
• [文献書誌] M.Takigawa: "Field-induced staggered magnetization near impurities in Sr_2CuO_3" Phys.Rev.B. 55. 14129-14132 (1997)
• [文献書誌] M.Knupfer: "Site-Specific unoccupied electronic structure of SrCuO_2" Phys.Rev.B. 55. R7291-7294 (1997)
• [文献書誌] T.Osafunc: "Optical Study of the Sr_<14-x>Ca_xCu_<24>O_<41> System" Phys.Rev.Lett.78. 1980-1983 (1997)
• [文献書誌] N.Motoyama: "Effect of Ca substiturisn and pressure on the transport of Sr_<14>Cu_<24>O_<41>" Phys.Rev.B. 55. R3386-3389 (1997)
• [文献書誌] M.Takigawa: "Spin and charge dynamics in the hole-dsped 1D-chain-ladder composite" Phys.Rev.B. 57. 1124-1140 (1998)
• [文献書誌] S.Uchida: "Josephson plasma in the c-aris optical spectrum of high-Tc Superconductors" Physica C. 293. 1-7 (1997)
• [文献書誌] C.Kim: "Separation of spin and charge excitations in one-dimensional SrCuO_2" Phys.Rev.B. 56. 15589-15595 (1997)
• [文献書誌] M.Matsuda: "Magnetic excitations and structural change in Sr_<14-x>Ca_xCu_<24>O_<41>" Phys.Rev.B. 56. 14499-14504 (1997)
• [文献書誌] S.Uchida: "Spin gap effects on the c-axis and in-plane charge clynamics of high-Tc cupsates" Physica C. 282-287. 12-18 (1997)
• [文献書誌] N.Mori: "Pressure-induced superconductivity in quantum spin-ladder compound" Physica B. 239. 137-140 (1997)
• [文献書誌] 上原 政智、秋光 純: "梯子格子の超伝導体" 日本物理学会誌. 52. 22-25 (1997)
• [文献書誌] N.Ogita et al.: "Raman Scattering Investigation of Y_2BaNiO_3" J.Phys.Soc.Jpn.3. 873-876 (1997)
• [文献書誌] T.Yokoo et al.: "Ni-chain gap excitations in (Nd_xY_<1-x>)_2BaNiO_5: 1D to 3-D crossover" Phys.Rev.B. 55. 11516-11520 (1997)
• [文献書誌] M.Hidaka et al.: "Re-examination of the room temperature crystal structure of CuGeO_3by X-ray dictraction experiments" J.Phys.: Condents Matter. 9. 809-824 (1997)
• [文献書誌] Y.Yamamoto et al.: "The Observation of g-shifts in Spin-Peierls Matcrial CuGeO_3 by submillimeter Wace ESR" J.Phys.Soc.Jpn.4. 1115-1123 (1997)
• [文献書誌] K.Motoya et al.: "Magnetic Property of CeNiC_2Studied by Macroscopic and Microscopic Measurements" J.Phys.Soc.Jpn.66. 1124-1129 (1997)
• [文献書誌] H.Nojiri et al.: "Magnetic phase diagram and antiferromagnetic resonance in CuGe_<1-y>Si_yO_3" J.Phys. : Condens Matter. 9. 1331-1338 (1997)
• [文献書誌] 秋光 純: "新しい高温超伝導体をデザインする" 第11回「大学と科学」公開シンポジウム. (1997)
• [文献書誌] H.Takahashi et al.: "Superconductivity in quantum spin-ladder compound Ca_<13.6>Sr_<0.4>Cu_<24>O_<41+δ>" Physica B. 237-238. 112-114 (1997)
• [文献書誌] K.Magishi et al.: "^<63>Cu NMR study on spin ladder compounds Sr_<14-x>Ca_xCu_<24>O_<41>(x=9,11.5)" Phyica C. 282-287. 1115-1116 (1997)
• [文献書誌] A.Yamashita et al.: "Anomalous Field Dependence of Magnetic Penetration Depth in the Volyro State of CcRu _2Probed by Muon Spin Rotation" Phys.Rev.Lett.79. 3771-3774 (1997)
• [文献書誌] T.Nagata et al.: "Superconductivity in the ladder compound Sr_<2.5>Ca_<11.5>Cu_<24>O_<41>" Physica C. 282-287. 153-156 (1997)
• [文献書誌] T.Tsuboi: "Nature of the vortex liquid in Bi_2Sr_2CaCu_2O_y" Phys.Rev.B. 55. R8709-R8712
• [文献書誌] H.Kitano: "Anisotropic quasiparticle conductivity in the superconducting state of high-T_e cuprates in microwave region" "proceedings of the 7th International Symposium on Superconductivity"Sapporo,Japan,October 30‐November 2,1996(Springe‐Verlag,Tokyo,1997). 127-130
• [文献書誌] T.Hanaguri: "Effects of columnar defects on the Josephson plasma resonance in Bi_2Sr_2CaCu_2O_y" Phys.Rev.Lett.78. 3177-3180
• [文献書誌] T.Tsuboi: "The static and dynamic properties of the vortices in Bi_2Sr_2CaCu_2O_y" Physica C. 282-287. 1303-1304
• [文献書誌] H.Kitano: "Out of plane microwave conductivity of the cuprates in the superdonducting state" Physica C. 282-287. 1125-1126
• [文献書誌] T.Hanaguri: "Josephson plasma resonance in the mixed state of Bi_2Sr_2CaCu_2O_y containing columnar defects" Physica C. 282-287. 2375-2376
• [文献書誌] X.M.Wang: "Dielectric response of the sliding SDW in (TMTSF)_2A_3F_6" Solid State Commun.(in press).
• [文献書誌] Y.Tsuchiya: "Josephson plasma resonance in the mixed state of heavy‐ion irradiated Bi_2Sr_2CaCu_2O_y" Physica C. 293. 254-258
• [文献書誌] A.Maeda: "Phase correlation investigated by the Josephson plasma resonance in Bi_2(Sr,La)_2CuO_y" Physica C. 293. 143-148
• [文献書誌] Y.Tsuchiya: "Effects of heavy‐ion irradiation on the Josephson plasma resonance in the mixed state of Bi_2Sr_2CaCu_2O_y" "Proceedings of the 8th International Symposimu on Superconductivity"Gifu,Japan,October 27‐30,1997(Springer‐Verlag,Tokyo,1998). in press
• [文献書誌] M.Goto: "Anisotropic transport properties of PrBa_2Cu_3O_7" Physica. C282-287. 1133-1134 (1997)