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-

1996 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 東京大学, 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

銅酸化物の異常金属相は,モット絶縁体相にドープされた正孔キャリア濃度pと温度TのT-p平面内において,T<T_0(p)(p【less than or equal】p_0,T(p_0)=0)の領域に明瞭に存在する。この異常金属相の形成と密接に結びついていると考えられる。本年度はこの異常相と"スピンギャップ"との関係を知るために厳密な意味での唯一の2次元スピンギャップ系であるCaV_4O_9の磁気励起スペクトルの特徴とその温度依存性とを詳しくしらべた。その結果,この系のスピンギャップ形式起源が解明されたばかりでなく,銅酸化物に対しても重要な情報が得られた。すなわちスピンギャップ温度としてよく知られた。T_<SG>(NMR 1/T_1Tが最大となる温度)より下ではじめてスピンギャップが形成されるわけでなく,もっと高い温度T_0から擬ギャップ形式がはじまっていると考えられることである。もっと直接的に言えば,T<T_0で現れる異常金属相自体がスピクギャップ形成(これはスピン-重項形式による)に伴ったものであり,さらにはそのスピン-重項の長距離秩序相が超伝導相である。T_cよりずっと高温側からのギャップ形成は光学測定や光電子分光によっても見られた。このように超伝導とスピンギャップとの関係が特に注目されるなかで,絶縁相がスピンギャップをもつ梯子型構造をもつ銅酸化物に正孔を注入して超伝導が本研究で見つかった。さらにはLa214系,Y123系の中性子散乱,NMR等を用いた詳細な研究により超伝導機構が磁気的なものであることを確認するデータが集積された。この他,1次元スピン系SrCuO_2の光電子分光によるスピン-電荷分離現象の観測,Sr_2RnO_4のNMR測定によるP波超伝導の可能性の指摘等がなされた。

研究成果

• [文献書誌] J.Takeda: "Compasion of Cu-Site Substilution Effects of Magnetic and Nonmagnetic Atoms on the Normal State Properties of Lazy Sry CuO_4 up to about 1000K" J.Phys.Soc.Jpn.65. 2946-2951 (1996)
• [文献書誌] T.Nishikawa: "Thermal Properties of Two Dimensional Mott System La_<1.17-X>Sr_X VS_<3.17>" J.Phys.Soc.Jpn.65. 2543-2547 (1996)
• [文献書誌] S.Tanaka: "Symmetry of the Superconducting Order Parameter of High-Tc Oxides and Consideration of the R-Dependent Tunneling in STM/STS" J.Phys.Soc.Jpn.65. 2212-2219 (1996)
• [文献書誌] H.Harashina: "Spin Structure of S=1/2 Quantum Spin System CaV_3O_7" J.Phys.Soc.Jpn.65. 1570-1573 (1996)
• [文献書誌] K.Kodama: "Evolution of Spin Gap Behavior in the Excitation Specha of Quasi-Two-Dimensional S=1/2 System CaV_4O_9" J.Phys.Soc.Jpn.65. 1941-1944 (1996)
• [文献書誌] H.Kamijo: "Electron and Magnon Contributions to the Thermal Cnductivity of YBa_2Cu_3O_<6+x> (0.1<x<0.9) at Low Temperatures" J.Phys.Soc.Jpn.65. 1551-1554 (1996)
• [文献書誌] Y.Yasui: "Strong Pressure Effects on the Electrical Resistivity of BaCo_<1-x> NixS_2" J.Phys.Jpn.65. 2757-2760 (1996)
• [文献書誌] Y.Kobayashi: "Transport and Magnetic Properties of La_3Ni_2O_<7-d> and La_4Ni_3O_<10-δ>" J.Phys.Soc.Jpn.65. 3978-3982 (1996)
• [文献書誌] S.Shamoto: "Neutron Scattering Studies of BaCo_<0.82>Nia_<18>S_2" J.Phys.Soc.Jpn.66(in press). (1997)
• [文献書誌] K.Kodama: "Study of Spin-Gap Formation in Quasi-Two-Dimensional S=1/2 System CaV_4O_9 : Neutron Scattering and NMR" J.Phys.Soc.Jpn.66(in press). (1997)
• [文献書誌] J.Takeda: "Thermal Expression Coefficient of BaCo_<1-x>NixS_2" J.Phys.Soc.Jpn.66(in press). (1997)
• [文献書誌] M.Ido: "STM/STS and Electronic Specific Heart of High-Tc Cuprates : Symmetry of the Order Parameter" Physica C. 263. 225-231 (1996)
• [文献書誌] M.Ido: "Pressure Effect on Anomalous Suppression of T_c around x=1/8 in La_<2-x>Ba_xcUO_4 and La_<1.8-x>Nd_<0.2>Ba_xCuO_4" Journal of Low Temperature Physics. 105. 311-316 (1996)
• [文献書誌] N.Momono: "Evidence for Nodes in the Superconducting Gap on La_<2-x>Sr_xCuO_4 : T^2 Dependence" Physica C. 264. 311-318 (1996)
• [文献書誌] M.Oda: "STM Images of a Superconducting Cu-O Plane and the Corresponding Tunneling Spectrum in Bi_2Sr_2CaCu_2O_<8+δ>" Phys.Rev.B. 53. 2253-2256 (1996)
• [文献書誌] T.Nakano: "T-Dependence of Spin Susceptibility of La_<2-x>Sr_xCuO_4" Journal of Low Temperature Physics. 105. 395-400 (1996)
• [文献書誌] M.Oda: "STM and STS Studies on the Super conducting Gap Symmetry of Bi_2Sr_2CaCu_2O_<8+δ>" Physica C. 263. 241-244 (1996)
• [文献書誌] C.H.Lee: "Anomalus Breaking of Phon on Softening in the Superconducting State of La_<1.85>Sr_<0.15>CuO_4" Physica C. 257. 264-270 (1996)
• [文献書誌] S.Wakimoto: "Excess Oxygen Doping in Single Crystals of La_<2-x>BixCuO_<4+δ> with or without Phase Separation" J.Phys.Soc.Jpn.65. 581-585 (1996)
• [文献書誌] T.Fukuda: "Dynamical Magnetic Structure of the Spin Density Wave State in Cr" J.Phys.Soc.Jpn.65. 1418-1426 (1996)
• [文献書誌] B.O.Wells: "Intercalation and Staging Behavior in Super-Oxygenated La_2CuO_4" Z.Phys.B. 100. 535-545 (1996)
• [文献書誌] K.Kurahashi: "Nondestructive Analysis and Control of Doping Rate in La_<2-x>(Bi,Sr)CuO_<4+y>" J.Phys.Soc.Jpn.65. 3994-3997 (1996)
• [文献書誌] K.Kojima: "Reduction of Ordered Moment and Neel Temperature of Quasi One Dimensional Antiferromagnet Sr_2CuO_3 and Ca_2CuO_3" Phys.Rev.Lett.(in press). (1997)
• [文献書誌] M.C.Martin: "Magnetism and Structural Distortion in the La_<0.7>Sr_<0.3>MnO_3" Phys.Rev.B. 53. 14285-14290 (1996)
• [文献書誌] N.Sato: "Anisotropy and Two Langth Scales in the Magnetic Critical Scattering in the Heavy-Fermion Superconductor UPa_2Al_3" Phys.Rev.B53. 14043-14046 (1996)
• [文献書誌] T.Yokoya: "High-resolution angle-resolved photoemission study of non-cuprate two-dimensional superconductor Sr_2RuO_4" J.Electron Spectroscopy and Related Phenomena. 78. 171-174 (1996)
• [文献書誌] A.Chainani: "Electronic structure of Fe_3O_4 across the Verwey transition" J.Electron Spectroscopy and Related Phenomena. 78. 99-102 (1996)
• [文献書誌] T.Yokoya: "Extended van-Hove singularity in a non cuprate layered superconductor Sr_2RuO_4" Phys.Rev.Lett.76. 3009-3012 (1996)
• [文献書誌] H.Ding: "Angle-resolved photoemission spectroscopy study of the superconducting gap anisotropy in Bi_2Sr_2CaCu_2O_<8+x>" Phys.Rev.B54. R9678-R9684 (1996)
• [文献書誌] T.Yokoya: "Extended van-Hove singularity in Sr_2RuO_4 observed by angle-resolved" Physica C. 263. 505-509 (1996)
• [文献書誌] T.Yokoya: "Evidence for Correlation Effects in Sr_2RuO_4 from Resonant and X-ray Photoemission Spectroscopy" Phys.Rev.B53. 8151-8154 (1996)
• [文献書誌] H.Ding: "Electronic excitation in Bi_2Sr_2CaCu_2O_8 : Fermi surface,dispersion,and absence of bilayer splitting" Phys.Rev.Lett.76. 1533-1536 (1996)
• [文献書誌] T.Yokoya: "High-resolution ARPES study formomentum dependence of superconducting gap in Bi_2Sr_2CaCu_2O_8" Phys.Rev.B53. 14055-14057 (1996)
• [文献書誌] J.C.Campuzano: "Direct observation of particle-hole mixing in the superconducting state by angle-resolved photoemission" Phys.Rev.B53. R14737-R14057 (1996)
• [文献書誌] H.Ding: "Spectroscopic evidence for a pseudogap in the normal state of underdoped high-Tc superconductors" Nature. 382. 51-54 (1996)
• [文献書誌] T.Yokoya: "Angle-resolved photoemission study of Sr_2RuO_4" Phys.Rev.B54. 13311-13318 (1996)
• [文献書誌] H.Ding: "Evolution of the Fermi surface with carrier concentration in Bi_2Sr_2CaCu_2O_<8+δ>" Phys.Rev.Lett.(in press).
• [文献書誌] J.M.Tranquada: "Coexistence of,and Competition between,Superconductivity and Charge Stripe Order" Phys.Rev.Latt.78. 338-341 (1997)
• [文献書誌] B.Nachumi: "Muon Spin Relaxation Studies of Zn-Substituted High-Tc Superconductors" Phys.Rev.Lett.77. 5421-5424 (1996)
• [文献書誌] G.S.Boebinger: "Insulator-to-Metal Crossover in the Normal State of La_<2-x>Sr_xCuO_4" Phys.Rev.Lett.77. 5417-5420 (1996)
• [文献書誌] Y.Ando: "Supprting Evidence of the Unusual Insulating Behavior of La_<2-x>Sr_xCuO_4" J.Low Temp.Phys.105. 867-875 (1996)
• [文献書誌] S.Uchida: "Optical Properties of High-Tc Superconductors" J.Low Temp.Phys.105. 723-732 (1996)
• [文献書誌] M.Matsuda: "Magnetic excitations from the singlet ground state in Sr_<14-x> Y_xCu_<24>O_<41>" Phys.Rev.B. 54. 12199-12206 (1996)
• [文献書誌] C.Kim: "Observation of Spin-Charge Separation in SrCuO_2" Phys.Rev.Lett.77. 4054-4057 (1996)
• [文献書誌] J.M.Transquada: "Neutron-scattering study of stripe-phase order in La_<1.48>Nd_<0.4>Sr_<0.12>CuO_4" Phys.Rev.B. 54. 7489-7499 (1996)
• [文献書誌] O.V.Misochko: "Raman-scttering evidence for free spinons in Sr_2CuO_3" Phys.Rev.B. 53. R14733-R14736 (1996)
• [文献書誌] S.Uchida: "c-axis spectra and charge dynamics in La_<2-x>Sr_xCuO_4" Phys.Rev.B. 53. 14558-14574 (1996)
• [文献書誌] S.Uchida: "Zn-doping effects on the charge dynamics in high-Tc copper oxides" Physia C. 263. 264-270 (1996)
• [文献書誌] M.Takigawa: "Dynamics in the S=1/2 One-Dimensional Antiferromagner Sr_2CuO_3" Phys.Rev.Lett.76. 4612-4615 (1996)
• [文献書誌] E.Pellegnn: "Ols near-edge x-ray absorphon of La_<2-x>Sr_xNiO_4" Phys.Rev.B. 53. 10667-10679 (1996)
• [文献書誌] S.Uchida: "Zn-Doping Effects on the Charge Transport in High Tc Copper Oxides" Chinese J.of Physics. 34. 423-431 (1996)
• [文献書誌] N.Motoyama: "Magnetic Susceptibility of Ideal Spin 1/2 Heisenberg Chain Systems" Phys.Rev.Lett.76. 3212-3215 (1996)
• [文献書誌] T.Kimura: "In-plane and out-of-plane majnetoresistance in LaP_<2-x>Sr_xCuO_4" Phys.Rev.B. 53. 8733-8742 (1996)
• [文献書誌] T.Hanaguri: "Cross over from the First Order Vortex Phase Transition tp the Peak" Physica C. 256. 111-118 (1996)
• [文献書誌] T.Hanaguri: "Doping level dependent magnetization anomalies and heat capacity of Bi_2Sr_2CaCu_2O_<8+δ> in the mixed state" Physica C. 263. 438-441 (1996)
• [文献書誌] A.Maeda: "Nonliar Meissner effect of the cuprate supercenductors investigated" Physica C. 263. 438-441 (1996)
• [文献書誌] Tsuboi: "High pecision mognetization and hear capacity measurements of Bi_2Sr_2CaCu_2O_y single crytals in the mixed state" Advances in Sperconductivity. V. 205-208 (1996)
• [文献書誌] A.Maeda: "Out-of plane quasi particle dynamics of the cuprate supercuductors below Tc in microwave region" J.Low Temp.Physics. 105. 323-328 (1996)
• [文献書誌] T.Hanaguri: "Plase fransitio in the mixed state of Bi_2Sr_2CaCu_2O_y oberved by locul and macroscopy magnetometry" Gech.J.Phys.46. 1559-1560 (1996)
• [文献書誌] A.Maeda: "Josephson-plasma resonance of Bi-cuprates" Gech.J.Phys.46. 1635-1636 (1996)
• [文献書誌] A.Maeda: "Nonlinear meissner effect in double loyered high Tc cuprates mestigatied by measurement of the peretration depth" J.Phys.Soc.Jpn.65. 3638-3645 (1996)
• [文献書誌] T.Shibauchi: "In-plane microwave conductivity and quasiparticle scutlering rate of superconducting high-Tc cuprates" J.Phys.Soc.Jpn. 65. 3266-3273 (1996)
• [文献書誌] H.Kitano: "Anisotropic quasiparticle conductivity in the superconducting state of high-Tc cuprates in microwave region" Adrances in Superconductivity. VI(in press). (1997)
• [文献書誌] A.Maeda: "Microwave absorption in the mixed state of (Bi or Tl)_2(Sr or Ba)_2 Ca_<n-1>CunOy" Advances in superconductivity. V. 185-188 (1996)
• [文献書誌] S.Sakamoto: "Josephson-plasma resonance in a single-layered cuprate Bi_2(Sr,La)_2 CuOy" Phys.Rev.B. 53. R14749-R14752 (1996)
• [文献書誌] T.Tsuboi: "Nature of the Vortex Liquid in Bi_2Sr_2CaCu_2Oy" Phys.Rev.B. (in press). (1996)
• [文献書誌] M.Arai: "Quantum Spin Excitations in the Spin Peierls System CuGeO_3" Phys,Rev.Lett.77. 3649-3652 (1996)
• [文献書誌] R.Kadono: "Long-Range Magnetic Ordering in the Spin Ladder Compound LaCuO_<2.5> Probed by Muon-Spin Relaxation" Phys.Rev.B. 54. R9628-R9630 (1996)
• [文献書誌] N.Ogita: "Raman Scattering in CuGeO_3" Physica B. 219-220. 107-109 (1996)
• [文献書誌] Y.Tsunezumi: "Absence of the Directric Anomaly at T_<sp> of CuGeO_3" J.Phys.Soc.Jpn.65. 3403-3404 (1996)
• [文献書誌] M.Steiner: "The change of the Symmetry of the Soft-mode Spin-flop Trnsition A_3 Observed in MnTiO_3 Using Indastic Polarized Neution Scattering" J.Phys.Condens.Matter. 8. 5905-5914 (1996)
• [文献書誌] T.Mizokawa: "Photoemission and X-Ray Absorption Spectroscopy of PrNiO_3" J.Electron Spectroscopy and Related Phenomena. 78. 191-194 (1996)
• [文献書誌] T.Sakaguchi: "Neutron Scattering Study of Magnetic Excitations in the Spin S=1 One Dimensional Heisenberg Artiferromagnet Y_2BaNiO_5" J.Phys.Soc.Jpn.65. 3025-3031 (1996)
• [文献書誌] M.Uehara: "Superconductivity in the S=1/2 Spin Ladder System Sr_<0.4>Ca_<13.6>Cu_<24>O_<41.84>" J.Phys.Soc.Jpn.65. 2764-2767 (1996)
• [文献書誌] 銭谷勇磁: "頂点臭素を含む超伝導体;(Ca,A)_2CuO_2Br_2 : A=Na,K" 粉末粉体. 43. 1087-1089 (1996)
• [文献書誌] 秋光純: "様子格子で超電動" パリティ. 12. 37-40 (1996)
• [文献書誌] 西正和: "スピンパイエルス系CuGeO_3の研究-中性子散乱実験を中心として-" 固体物理. 31. 899-907 (1996)
• [文献書誌] M.Sato: "Effect of pressure on Tc of a homologous serles of oxycarbonate superconductors Sp_2(Ca,Sr)_<n-1>Cu_n(CO_3)_<1-x>(BO_3)_xO_y(n=1,2) and Ba_2Ca_2Cu_3(CO_3)_<1-x>(BO_3)_xO_y" Physica C. 271. 79-82 (1996)
• [文献書誌] T.Ekino: "Tunneling Spectroscopy of Superconducting Energy Gap in RNi_2B_2C(R=Y and Lu)" Phys.Rev.B. 53. 5640-5649 (1996)
• [文献書誌] J.Akimitsu: "Metal-Insulator Transition in the S=1/2 Spin Ladder System (Sr_<0.4>Ca_<0.6>)_<14>Cu_<24-x>CoxO_<41-δ>" Physica C. 263. 475-481 (1996)
• [文献書誌] H.Nakata: "The Phace Diagram of the New Superconductor Sr_2CuO_2(CO_3)_<1-x>(BO_3)_x" Physica C. 263. 344-348 (1996)
• [文献書誌] I.Yamada: "Electron Paramagnetic Resonance Governed by the Dzyaloshinsky-Moriya Antisymmetric Exchange Interaction in CuGeO_3" J.Phys,: Condensed Matt.8. 2625-2640 (1996)
• [文献書誌] 上原政智: "梯子型構造を有する銅酸化物へのキャリアド-ピング" 応用物理学会誌. 65. 394-400 (1996)
• [文献書誌] M.C.Martin: "Temperature Dependence of the Spin-Pecerls Energy Gap and Anomalous Line Shape in CuGeO_3" Phys.Rev.B. 53. R14713-R14716 (1996)
• [文献書誌] K.Magishi: "Magnetic excitation and superconductivity in overdoped TlSr_2CaCu_2O_<7-δ> : A ^<63>Cu NMR Sbudy" Physical Review B. 54. 10131-10142 (1996)
• [文献書誌] K.Asayama: "NMR of high Tc Superconductor" Czechoslovak Tc of Physics. 46. 3187-3194 (1996)
• [文献書誌] K.Ishida: "Anisotropic pairing in Superconducting Sr_2RuO_4 (Tc〜0.7K)" Proc.M^2S-HTSC-V,in Beijng,1997. (in press).
• [文献書誌] Y.Tokunaga: "Cu NQR Study of Spin fluc ation in Ni Substituted YBa_2Cu_3O_7" Proc.M^2S-HTSC-V,in Beijing,1997. (in press).
• [文献書誌] K.Magishi: "^<63>Cu NHR Study on spin ladder compound Sr_<14-x>Ca_xCu_<24>O_<41> (x=9,11.5)" Physica C. (in press). (1997)
• [文献書誌] F.Nakamura: "Pressure Dependence of Out of Plane Conduction in La_<2-x> Sr_xCuO_4" Phys.Rev.B. 54. 10061-10064 (1996)
• [文献書誌] K.Yoshida: "Anisotropic Flux Pinning in a Layered Superconductor Sr_2RuO_4" J.Phys.Soc.Jpn.65. 2220-2226 (1996)
• [文献書誌] S.Sakita: "Elastic Softening in Single-Crystalline La_<2-x>Sr_xCuO_4 around 1/8" Physica B. 219/220. 216-218 (1996)
• [文献書誌] M.Udagawa: "Phonon Raman Scattering of Sr_2RuO_4" Physica B. 219/220. 222-224 (1996)
• [文献書誌] F.Nakamura: "Transport Properties of Detwinned Crystals of La_<2-x>Sr_xCuO_4" Physica C. 263. 282-285 (1996)
• [文献書誌] K.Yoshida: "Anisotropic Superronductivity of Sr_2RuO_4" Physica C. 263. 519-522 (1996)
• [文献書誌] X.Z.BaO: "Relation between Transport,Structural and Superconductive properties in La_<2-x-y>NdyBaxCuO_4" Physica C. 271. 256-264 (1996)
• [文献書誌] F.Nakamura: "Pressure Effects of Resistivity along the C axis in La_<2-x>Sr_xCuO_4" J.Low Temp.Phys.105. 915-920 (1996)
• [文献書誌] K.Yoshida: "Crossover from 3D to 2D Metalic Conduction in Sr_2RuO_4" J.Low Temp.Phys.105. 1593-1598 (1996)
• [文献書誌] M.Udagawa: "Raman Scattering of La_2CuO_<4+δ>" Czech.J.Phys.46・S2. 1115-1116 (1996)