電子ドープ型銅酸化物の中性子散乱による磁気相関と高温超伝導の普遍的関係の解明

• Project/Area Number: 17684016
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics II
• Research Institution: Tohoku University
• Principal Investigator: 藤田 全基 Tohoku University, 金属材料研究所, 助教 (20303894)
• Project Period (FY): 2005 – 2007
• Project Status: Completed (Fiscal Year 2007)
• Budget Amount: ¥19,890,000 (Direct Cost: ¥15,300,000、Indirect Cost: ¥4,590,000); Fiscal Year 2007: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000); Fiscal Year 2006: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000); Fiscal Year 2005: ¥13,910,000 (Direct Cost: ¥10,700,000、Indirect Cost: ¥3,210,000)
• Keywords: 電子ドープ型高温超伝導 / 中性子散乱 / 磁気相関 / 単結晶育成 / 構造解析

Research Abstract

19年度も、電子ドープ型超伝導体における磁気相関の研究を中性子散乱実験を中心に進めた。ホールドープ系では、低エネルギー領域の格子非整合磁気相関と超伝導の密接な関係性が、系統的な研究により示されている。また、ドープによる高エネルギー磁気相関の変化についても調べられており、超伝導相では「砂時計型」の励起スペクトルの存在が報告されている。一方、電子ドープ系では、ホールドープ系とは対照的に、(π,π)点を中心とした格子整合な低エネルギー相関が超伝導相で観測されることをこれまでに我々の研究で明らかにした。本年度は、高エネルギーまでの励起スペクトルがドーピングによりどのように変化するのかを明らかにするため、パルス中性子源を利用した実験を行い、その詳細を解析で明らかにした。その結果、これまでに我々が明らかにした最適ドープ組成の励起スペクトルに比べ、電子を過剰にドープしたPr^<l-x>LaCe^xCuO_4では、エネルギー遷移100meVの高エネルギー領域に磁気励起状態が存在するものの、最適組成試料に比べて散乱強度は約半分に減少していることを見いだした。また低エネルギー領域での格子整合なピークもエネルギーの上昇に対して著しく増加している。これらのことは、電子ドープによりー磁気相関が顕著に弱まることを示唆しており、ホールドール系との比較からは、磁気相関のドーピングに対する変化の仕方に、高エネルギー領域までの電子・ホール非対称性が存在することを意味している。

Research Products

• [Journal Article] High-energy magnetic excitations from dynamic stripes in La_<1.875> Ba_<0.125> CuO_4 (2007)
  • Author(s): Guangyong Xu
  • Journal Title: Physical Review B 76
  • Peer Reviewed
• [Journal Article] Pulsed neutron-scattering study of an entire spin excitations in the electron-doped high-T_c superconductor (2007)
  • Author(s): M.Fujita
  • Journal Title: Physica C 460-462 Pages: 44-47
  • Peer Reviewed
• [Journal Article] Spin Correlations in Electron-Doped High-T_c Superconductor (2007)
  • Author(s): M. Fujita
  • Journal Title: J. Phys. and Chem. of Solid 68 Pages: 2035-2038
  • Peer Reviewed
• [Journal Article] Electron-Phonon Anomaly Related to Charge Stripes: Static Stripe Phase Versus Optimally Doped Superconducting La_<1.85>Sr_<0.15>CuO_4 (2007)
  • Author(s): D. Reznik
  • Journal Title: Physica C 460-462 Pages: 353-364
  • Peer Reviewed
• [Journal Article] Neutron-scattering study on spin fluctuations in high-temperature-tetragonal phase of La_<1.70>Sr_<0.24>Ce_<0.06>CuO_4 (2007)
  • Author(s): M. Enoki
  • Journal Title: J. Phys. and Chem. of Solid. 68 Pages: 2111-2114
  • Peer Reviewed
• [Journal Article] Photoemission study of the superconducting-gap symmetry in electron-doped high-T_c superconductors (2007)
  • Author(s): M. Fujita
  • Journal Title: J. Phys. and Chem. of Solid 68 Pages: 2035-2038
  • Peer Reviewed
• [Journal Article] Pulsed neutron-scattering study of an entire spin excitations in the electron-doped high-T_c superconductor (2007)
  • Author(s): H. Matsui
  • Journal Title: Physica C 460-462 Pages: 862-863
  • Peer Reviewed
• [Journal Article] Magnetic correlations and superconductivity in La_<1.93>Sr_<0.07>CuO_4 revealed by μSR (2007)
  • Author(s): K. Ishida
  • Journal Title: Journal of Magnetism and Magnetic Materials 310 Pages: 526-528
  • Peer Reviewed
• [Journal Article] Novel Spin Excitations in Optimally Electron-Doped Pr_<0.89>LaCe_<0.11>CuO_4 (2006)
  • Author(s): Masaki FUJITA
  • Journal Title: J. Phys. Soc. Jpn. 75
  • NAID: 110004789063
• [Journal Article] Universal magnetic excitation spectrum in cuprates (2006)
  • Author(s): J.M.Tranquada
  • Journal Title: Journal of Physics and Chemistry of Solids 67 Pages: 511-515
• [Journal Article] Incommensurate Lattice Distortion in the High Temperature Tetragonal Phase of La_2(Sr,Ba)_xCuO_4 (2006)
  • Author(s): Shuichi WAKIMOTO
  • Journal Title: J. Phys. Soc. Jpn. 75
• [Journal Article] Electron-phonon coupling reflecting dynamic charge inhomogeneity in copperoxide superconductors (2006)
  • Author(s): D.Reznik
  • Journal Title: Nature 440 Pages: 1170-1173
• [Journal Article] Impurity effect on the diagonal incommensurate spin correlations in La_<2-x>Sr_xCuO_4 (2006)
  • Author(s): M.Matsuda
  • Journal Title: Phys. Rev. B 73
• [Journal Article] Effects of superconductivity and charge order on the subterahertz reflectivity of La_<1.875>Ba_<0.125-y>Sr_yCuO_4 (2006)
  • Author(s): M.Ortolani
  • Journal Title: Phys. Rev. B 73
• [Journal Article] Neutron scattering study on stripe correlations in La_<2-x>Ba_xCuO_4 (2005)
  • Author(s): M.Fujita
  • Journal Title: Physica C 426-431 Pages: 257-261
• [Journal Article] Soft Phonons and Structural Phase Transitions in La_<1.875>Ba_<0.125>CuO_4 (2005)
  • Author(s): H.Kimura
  • Journal Title: J.Phys.Soc.Jpn. 74 Pages: 445-449
• [Journal Article] Field-Induced Uniform Antiferromagnetic Order Associated with Superconductivity in Pr_<1-x>LaCe_xCuO_4 (2005)
  • Author(s): R.Kadono
  • Journal Title: J.Phys.Soc.Jpn. 74 Pages: 2806-2812
• [Journal Article] X-ray and Electron Diffraction Study of a Precipitation Phase in Nd_<1.85>Ce_<0.15>CuO_4 y Single Crystal (2005)
  • Author(s): H.Kimura
  • Journal Title: J.Phys.Soc.Jpn. 74 Pages: 2282-2286
• [Journal Article] Direct Observation of a Nonmonotonic d_x^2-_y^2-Wave Superconducting Gap in the Electron-Doped High-T_c Superconductor Pr_<1-x>LaCe_xCuO_4 (2005)
  • Author(s): H.Matsui
  • Journal Title: Phys.Rev.Lett 95
• [Journal Article] Magnetic excitations from the linear Heisenberg antiferromagnetic spin trimer system A_3Cu_3(PO_4)_4 (A=Ca,Sr,and Pb) (2005)
  • Author(s): M.Matsuda
  • Journal Title: Phys.Rev.B 71
• [Presentation] Doping and temperature evolutions of spin correlations in electron-doped Pr_<1-x>LaCe_xCuO_4 (2007)
  • Author(s): M. Fujita
  • Organizer: 20th International Symposium on Superconductivity
  • Place of Presentation: Tsukuba, Japan
  • Year and Date: 2007-11-06
• [Presentation] Doping and temperature dependences of low-energy spin excitations in electron-doped high-T_c superconductor Pr_<1-x>LaCe_xCuO_4 (2007)
  • Author(s): M. Nakagawa
  • Organizer: International Conference on Spectroscopies in Novel Superconductors
  • Place of Presentation: Sendai, Japan
  • Year and Date: 2007-08-23
• [Presentation] Fe-doping-induced charge-density-wave order in La_<1.88-y>Sr_<0.12+y>Cu_<1-y>Fe_yO_4 (2007)
  • Author(s): M. Fujita
  • Organizer: International Conference on Spectroscopies in Novel Superconductors
  • Place of Presentation: Sendai, Japan
  • Year and Date: 2007-08-20
• [Presentation] Neutron-Scattering study of spin correlations in La_<1.94-x>Sr_xCe_<0.06>CuO_4 (2007)
  • Author(s): M. Enoki
  • Organizer: International Conference on Spectroscopies in Novel Superconductors
  • Place of Presentation: Sendai, Japan
  • Year and Date: 2007-08-20
• [Presentation] Neutron-scattering study of impurity effects on the stripe order in high-T_c cuprate (2007)
  • Author(s): M. Fujita
  • Organizer: International Conference on Strongly Correlated Electron Systems
  • Place of Presentation: Houston, USA
  • Year and Date: 2007-05-18
• [Presentation] High-Energy Spin Excitations in Overdoped Pr_<1-x>LaCe_xCuO_4 (2007)
  • Author(s): M. Fujita
  • Organizer: International Symposium on Lattice Effects in Cuprate High Temperature Superconductor
  • Place of Presentation: Tsukuba, Japan