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 Fiscal Year Annual Research Report

• Project/Area Number: 07237105
• Research Institution: Nagoya University
• Principal Investigator: 佐藤 正俊 名古屋大学, 大学院・理学研究科, 教授 (40092225)
• Co-Investigator(Kenkyū-buntansha): 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)
• Keywords: 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

Research Abstract

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。

Research Products

• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] H.Harashina: "Spin Structure of S=1/2 Quantum Spin System CaV_3O_7" J.Phys.Soc.Jpn.65. 1570-1573 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] Y.Yasui: "Strong Pressure Effects on the Electrical Resistivity of BaCo_<1-x> NixS_2" J.Phys.Jpn.65. 2757-2760 (1996)
• [Publications] 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)
• [Publications] S.Shamoto: "Neutron Scattering Studies of BaCo_<0.82>Nia_<18>S_2" J.Phys.Soc.Jpn.66(in press). (1997)
• [Publications] 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)
• [Publications] J.Takeda: "Thermal Expression Coefficient of BaCo_<1-x>NixS_2" J.Phys.Soc.Jpn.66(in press). (1997)
• [Publications] M.Ido: "STM/STS and Electronic Specific Heart of High-Tc Cuprates : Symmetry of the Order Parameter" Physica C. 263. 225-231 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] T.Nakano: "T-Dependence of Spin Susceptibility of La_<2-x>Sr_xCuO_4" Journal of Low Temperature Physics. 105. 395-400 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] T.Fukuda: "Dynamical Magnetic Structure of the Spin Density Wave State in Cr" J.Phys.Soc.Jpn.65. 1418-1426 (1996)
• [Publications] B.O.Wells: "Intercalation and Staging Behavior in Super-Oxygenated La_2CuO_4" Z.Phys.B. 100. 535-545 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] M.C.Martin: "Magnetism and Structural Distortion in the La_<0.7>Sr_<0.3>MnO_3" Phys.Rev.B. 53. 14285-14290 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] A.Chainani: "Electronic structure of Fe_3O_4 across the Verwey transition" J.Electron Spectroscopy and Related Phenomena. 78. 99-102 (1996)
• [Publications] T.Yokoya: "Extended van-Hove singularity in a non cuprate layered superconductor Sr_2RuO_4" Phys.Rev.Lett.76. 3009-3012 (1996)
• [Publications] 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)
• [Publications] T.Yokoya: "Extended van-Hove singularity in Sr_2RuO_4 observed by angle-resolved" Physica C. 263. 505-509 (1996)
• [Publications] T.Yokoya: "Evidence for Correlation Effects in Sr_2RuO_4 from Resonant and X-ray Photoemission Spectroscopy" Phys.Rev.B53. 8151-8154 (1996)
• [Publications] 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)
• [Publications] T.Yokoya: "High-resolution ARPES study formomentum dependence of superconducting gap in Bi_2Sr_2CaCu_2O_8" Phys.Rev.B53. 14055-14057 (1996)
• [Publications] J.C.Campuzano: "Direct observation of particle-hole mixing in the superconducting state by angle-resolved photoemission" Phys.Rev.B53. R14737-R14057 (1996)
• [Publications] H.Ding: "Spectroscopic evidence for a pseudogap in the normal state of underdoped high-Tc superconductors" Nature. 382. 51-54 (1996)
• [Publications] T.Yokoya: "Angle-resolved photoemission study of Sr_2RuO_4" Phys.Rev.B54. 13311-13318 (1996)
• [Publications] H.Ding: "Evolution of the Fermi surface with carrier concentration in Bi_2Sr_2CaCu_2O_<8+δ>" Phys.Rev.Lett.(in press).
• [Publications] J.M.Tranquada: "Coexistence of,and Competition between,Superconductivity and Charge Stripe Order" Phys.Rev.Latt.78. 338-341 (1997)
• [Publications] B.Nachumi: "Muon Spin Relaxation Studies of Zn-Substituted High-Tc Superconductors" Phys.Rev.Lett.77. 5421-5424 (1996)
• [Publications] 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)
• [Publications] Y.Ando: "Supprting Evidence of the Unusual Insulating Behavior of La_<2-x>Sr_xCuO_4" J.Low Temp.Phys.105. 867-875 (1996)
• [Publications] S.Uchida: "Optical Properties of High-Tc Superconductors" J.Low Temp.Phys.105. 723-732 (1996)
• [Publications] 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)
• [Publications] C.Kim: "Observation of Spin-Charge Separation in SrCuO_2" Phys.Rev.Lett.77. 4054-4057 (1996)
• [Publications] 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)
• [Publications] O.V.Misochko: "Raman-scttering evidence for free spinons in Sr_2CuO_3" Phys.Rev.B. 53. R14733-R14736 (1996)
• [Publications] S.Uchida: "c-axis spectra and charge dynamics in La_<2-x>Sr_xCuO_4" Phys.Rev.B. 53. 14558-14574 (1996)
• [Publications] S.Uchida: "Zn-doping effects on the charge dynamics in high-Tc copper oxides" Physia C. 263. 264-270 (1996)
• [Publications] M.Takigawa: "Dynamics in the S=1/2 One-Dimensional Antiferromagner Sr_2CuO_3" Phys.Rev.Lett.76. 4612-4615 (1996)
• [Publications] E.Pellegnn: "Ols near-edge x-ray absorphon of La_<2-x>Sr_xNiO_4" Phys.Rev.B. 53. 10667-10679 (1996)
• [Publications] S.Uchida: "Zn-Doping Effects on the Charge Transport in High Tc Copper Oxides" Chinese J.of Physics. 34. 423-431 (1996)
• [Publications] N.Motoyama: "Magnetic Susceptibility of Ideal Spin 1/2 Heisenberg Chain Systems" Phys.Rev.Lett.76. 3212-3215 (1996)
• [Publications] T.Kimura: "In-plane and out-of-plane majnetoresistance in LaP_<2-x>Sr_xCuO_4" Phys.Rev.B. 53. 8733-8742 (1996)
• [Publications] T.Hanaguri: "Cross over from the First Order Vortex Phase Transition tp the Peak" Physica C. 256. 111-118 (1996)
• [Publications] 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)
• [Publications] A.Maeda: "Nonliar Meissner effect of the cuprate supercenductors investigated" Physica C. 263. 438-441 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] A.Maeda: "Josephson-plasma resonance of Bi-cuprates" Gech.J.Phys.46. 1635-1636 (1996)
• [Publications] 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)
• [Publications] T.Shibauchi: "In-plane microwave conductivity and quasiparticle scutlering rate of superconducting high-Tc cuprates" J.Phys.Soc.Jpn. 65. 3266-3273 (1996)
• [Publications] H.Kitano: "Anisotropic quasiparticle conductivity in the superconducting state of high-Tc cuprates in microwave region" Adrances in Superconductivity. VI(in press). (1997)
• [Publications] 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)
• [Publications] S.Sakamoto: "Josephson-plasma resonance in a single-layered cuprate Bi_2(Sr,La)_2 CuOy" Phys.Rev.B. 53. R14749-R14752 (1996)
• [Publications] T.Tsuboi: "Nature of the Vortex Liquid in Bi_2Sr_2CaCu_2Oy" Phys.Rev.B. (in press). (1996)
• [Publications] M.Arai: "Quantum Spin Excitations in the Spin Peierls System CuGeO_3" Phys,Rev.Lett.77. 3649-3652 (1996)
• [Publications] 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)
• [Publications] N.Ogita: "Raman Scattering in CuGeO_3" Physica B. 219-220. 107-109 (1996)
• [Publications] Y.Tsunezumi: "Absence of the Directric Anomaly at T_<sp> of CuGeO_3" J.Phys.Soc.Jpn.65. 3403-3404 (1996)
• [Publications] 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)
• [Publications] T.Mizokawa: "Photoemission and X-Ray Absorption Spectroscopy of PrNiO_3" J.Electron Spectroscopy and Related Phenomena. 78. 191-194 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] 秋光純: "様子格子で超電動" パリティ. 12. 37-40 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] T.Ekino: "Tunneling Spectroscopy of Superconducting Energy Gap in RNi_2B_2C(R=Y and Lu)" Phys.Rev.B. 53. 5640-5649 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] I.Yamada: "Electron Paramagnetic Resonance Governed by the Dzyaloshinsky-Moriya Antisymmetric Exchange Interaction in CuGeO_3" J.Phys,: Condensed Matt.8. 2625-2640 (1996)
• [Publications] 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)
• [Publications] 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)
• [Publications] 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)
• [Publications] K.Asayama: "NMR of high Tc Superconductor" Czechoslovak Tc of Physics. 46. 3187-3194 (1996)
• [Publications] K.Ishida: "Anisotropic pairing in Superconducting Sr_2RuO_4 (Tc〜0.7K)" Proc.M^2S-HTSC-V,in Beijng,1997. (in press).
• [Publications] 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).
• [Publications] 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)
• [Publications] F.Nakamura: "Pressure Dependence of Out of Plane Conduction in La_<2-x> Sr_xCuO_4" Phys.Rev.B. 54. 10061-10064 (1996)
• [Publications] K.Yoshida: "Anisotropic Flux Pinning in a Layered Superconductor Sr_2RuO_4" J.Phys.Soc.Jpn.65. 2220-2226 (1996)
• [Publications] S.Sakita: "Elastic Softening in Single-Crystalline La_<2-x>Sr_xCuO_4 around 1/8" Physica B. 219/220. 216-218 (1996)
• [Publications] M.Udagawa: "Phonon Raman Scattering of Sr_2RuO_4" Physica B. 219/220. 222-224 (1996)
• [Publications] F.Nakamura: "Transport Properties of Detwinned Crystals of La_<2-x>Sr_xCuO_4" Physica C. 263. 282-285 (1996)
• [Publications] K.Yoshida: "Anisotropic Superronductivity of Sr_2RuO_4" Physica C. 263. 519-522 (1996)
• [Publications] X.Z.BaO: "Relation between Transport,Structural and Superconductive properties in La_<2-x-y>NdyBaxCuO_4" Physica C. 271. 256-264 (1996)
• [Publications] 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)
• [Publications] K.Yoshida: "Crossover from 3D to 2D Metalic Conduction in Sr_2RuO_4" J.Low Temp.Phys.105. 1593-1598 (1996)
• [Publications] M.Udagawa: "Raman Scattering of La_2CuO_<4+δ>" Czech.J.Phys.46・S2. 1115-1116 (1996)