1992 Fiscal Year Annual Research Report

新しい物質設計指針に基づく高温超伝導体の開発

Research Project

Project/Area Number	03101003
Research Institution	Aoyama Gakuin University
Principal Investigator	秋光純青山学院大学, 理工学部, 教授 (80013522)
Co-Investigator(Kenkyū-buntansha)	藤森淳東京大学, 理学部, 助教授 (10209108) 十倉好紀東京大学, 理学部, 助教授 (30143382)
Keywords	超伝導体の物質設計 / 炭酸基超伝導体 / 金属一絶縁体転移 / 強相関電子系 / 電子有効質量 / 光電子分光 / 高圧合成 / ギャップ内状態
Research Abstract	新しい物質設計指針に基づいて、炭酸基(CO_3)を含む一連の新しい超伝導体を発見した。 (1) (Ln_<1-x>Ca_x)(SrBa)_2Cu_<2+y>(CO_3)_<1-y>O_z:(Ln:希土類元素) Tc=60〜80K、構造はいわゆる1-2-3構造のCu(I)サイトがCO_3基で置換されている。 (2) (Ln_<1-x>Ce_x)_2Sr_2Cu_<2+y>(CO_3)_<1-y>O_z:(Ln:希土類元素) Tc=27K、構造は蛍石型ブロック層と炭酸基が組合わさった構造である。 (3) Bi_2Sr_4Cu_2(CO_3)O_8 Tc=60K、その他にフッ素をドープした無限層構造の高圧合成、非銅系化合物 Ba_<1-x>Tl_xBiO_3、Y_2PdO_4の合成に成功した。非銅系の高温超伝導体探索の目的をかねて、チタン・バナジウム・ニッケル酸化物の物質合成の詳細について集中的に研究した。特に分光学的手法により、強相関電子系に特徴的な電子構造の変化(ギャップ内状態、キャリアードーピングによる金属絶縁体転移、電子有効質量の増大など)を解明しつつある。具体的なテーマとしては 1) ホールドープ系(La_<1-x>Sr_x)TiO_3,(Y_<1-x>Ca_x)TiO_3の電子相図・電子構造の解明 2) 銅・ニッケル酸化物ペロブスカイト(La_<1-x>Y_x)CuO_3,LnNiO_3などの高圧合成を行って電子相図を作成した更に、214系特に(Pr_<1-x>Ce_x)_2CuO_4の大型単結晶を作製して光スペクトルの測定を行い、いわゆるギャップ内状態を観測した。金属-絶縁体転移にともなう遷移金属酸化物の電子状態の変化を、光電子分光法およびX線吸収分光法を用いて明らかにした。とくに、バンドギャップの開閉による金属絶縁体転移およびキャリアーのドーピングによる金属絶縁体転移のそれぞれについて、ギャップ内状態の出現、フェルミ準位のシフトに関する一般的な法則を見い出した。種々の遷移金属酸化物・硫化物の電子状態を特徴づけるパラメーターの系統性をもとに、種々の物性予測(バンドギャップの大きさ、共有結合性の大きさ、ドープされたキャリアーの電荷分布など)を行い、実測値が存在するものについては、これと良い一致を得た。

Research Products

(22 results)

All Other

All Publications (22 results)

[Publications] J.Akimitsu et al.: "Superconductivity in the new compound (Y_<1-x>Ca_x)_<0.95>Sr_<2.05>Cu_<2.4>(CO_3)_<0.6>O_y" Physica C. vol.201. 320-324 (1992)
[Publications] Y.Miyazaki et al.: "(C_<0.35>Cu_<0.65>)Sr_2(Y_<0.73>Ce_<0.27>)_2Cu_2O_x:A new superconductor containing CO_3" Physica C. vol.202. 162-166 (1992)
[Publications] 秋光純他: "新超伝導体探索研究の現状と展望" 日本結晶学会誌. vol.34. 273-282 (1992)
[Publications] J.Akimitsu: "High-Tc superconductors based on the new material design" Phase Transitions. vol.41. 13-19 (1993)
[Publications] H.Takahashi et al.: "High pressure study on the superconducting transition temperature and Hall coefficient of Ba_<1-x>K_xBiO_3up to 8GPa" Physica C.
[Publications] T.Den et al.: "Superconductor with Tc up tu 80K in the compound (Ln,Ca)(Sr,Ba)_2(C,Cu)Cu_2O_<7-y>" Physica C(to be published).
[Publications] T.Ekino et al.: "Superconducting energy gaps in Bi_2Sr_2Cu_<6+y> and Ndsubstituted Bi_2Sr_<2-x>Nd_xCuO_<6+y>" Physica C.
[Publications] S.Noma et al.: "New Superconducting Phase in Nb_<1-x>Ta_xSe_3(0.135_<<X<.>16)" Physical Review B.
[Publications] Y.Tokura et al.: "Pressure dependence of charge-transfer-type gaps in CuO_2 layered compounds." Physical Review B. vol.45. 7581-7584 (1992)
[Publications] Y.Fujishima et al.: "Optical conductivity spectra of Sr_<1-x>La_xTiO_3:Filling-dependent effect of the electron correlation" Physical Review B. vol.46. 11167-11170 (1992)
[Publications] M.Kasuya et al.: "Optical spectra of Y_<1-x>Ca_xVO_3:Change of electronic structures with hole doping in Mott-Hubbard insulators" Physical Review B. vol.47. (1992)
[Publications] Y.Tokura: "Fillingness dependence of electronic structures in strong correlated electron systems : titanates and vanadates" J.Phys.Chem.Solids. vol.53. 1619-1625 (1993)
[Publications] H.Sato et al.: "La_<2-x>Sr_xCuO_4(110)thin films epitaxially grown along the CuO_2plane on Pr_2CuO_4Single crystals" Applied Physics Letters. vol.61. 2470-2472 (1992)
[Publications] M.Abbate at al.: "Controlled-Valence Properties of La_<1-x>Sr_xFeO_3and La_<1-x>Sr_xMnO_3 Studied by Soft X-ray Absorption Spectroscopy" Physical Review B. vol.46. 4511-4519 (1992)
[Publications] A.Fujimori et al.: "Doping-Induced changes on the Electronic Structure of La_xsSr_<1-X>TiO_3:Limitation of the One-Electron Rigid-Band Model and the Hubbard Model" Physical Review B. vol.46. 9841-9844 (1992)
[Publications] A.Fujimori et al.: "Evolution of the Spectral Function in Mott-Hubbard Systems with d^1 configuration" Physical Review B. vol.69. 1796-1799 (1992)
[Publications] I.H.Inoue et al.: "Electronic States in Valence Fluctuating Organic Conductor (R_1,R_2,-DCNθI)_2Cu Studied by Ultraviolet Photoemission Spectroscopy" Physical Reviw B.
[Publications] M.Abbate et al.: "Soft X-Ray Absorption Spectroscopy of Valence Oxides" Journal of Electron Spectroscopy and Related Phenomena.
[Publications] A.E.Bocquet et al.: "Electronic Structure of 3d Transiton-Metal Compounds by Analysis of Metal 2p Core-Level Photoemission Spectra" Physica Review B. vol.46. 3771-3784 (1992)
[Publications] A.Fujimori: "Electronic Structure of Metallic Oxides:Band Gap Closure and Valence Control" Journal of Physics and Chemistry of Solids. vol.53. 1595-1602 (1992)
[Publications] A.Fujimori et al.: "Evolution of the Spectral Function in Mott Hubbard Systems across Metal-Insulator Transitions" Physica B.
[Publications] 藤森淳: "X線光電子分光(XPS)および紫外線光電子分光(UPS)による高温超伝導体の研究" NSMF News. vol.33. 28-32 (1992)

1992 Fiscal Year Annual Research Report

新しい物質設計指針に基づく高温超伝導体の開発

Principal Investigator

秋光 純 青山学院大学, 理工学部, 教授 (80013522)

Research Products

[Publications] J.Akimitsu et al.: "Superconductivity in the new compound (Y_<1-x>Ca_x)_<0.95>Sr_<2.05>Cu_<2.4>(CO_3)_<0.6>O_y" Physica C. vol.201. 320-324 (1992)

[Publications] Y.Miyazaki et al.: "(C_<0.35>Cu_<0.65>)Sr_2(Y_<0.73>Ce_<0.27>)_2Cu_2O_x:A new superconductor containing CO_3" Physica C. vol.202. 162-166 (1992)

[Publications] 秋光 純 他: "新超伝導体探索研究の現状と展望" 日本結晶学会誌. vol.34. 273-282 (1992)

[Publications] J.Akimitsu: "High-Tc superconductors based on the new material design" Phase Transitions. vol.41. 13-19 (1993)

[Publications] H.Takahashi et al.: "High pressure study on the superconducting transition temperature and Hall coefficient of Ba_<1-x>K_xBiO_3up to 8GPa" Physica C.

[Publications] T.Den et al.: "Superconductor with Tc up tu 80K in the compound (Ln,Ca)(Sr,Ba)_2(C,Cu)Cu_2O_<7-y>" Physica C(to be published).

[Publications] T.Ekino et al.: "Superconducting energy gaps in Bi_2Sr_2Cu_<6+y> and Ndsubstituted Bi_2Sr_<2-x>Nd_xCuO_<6+y>" Physica C.

[Publications] S.Noma et al.: "New Superconducting Phase in Nb_<1-x>Ta_xSe_3(0.135_<<X<.>16)" Physical Review B.

[Publications] Y.Tokura et al.: "Pressure dependence of charge-transfer-type gaps in CuO_2 layered compounds." Physical Review B. vol.45. 7581-7584 (1992)

[Publications] Y.Fujishima et al.: "Optical conductivity spectra of Sr_<1-x>La_xTiO_3:Filling-dependent effect of the electron correlation" Physical Review B. vol.46. 11167-11170 (1992)

[Publications] M.Kasuya et al.: "Optical spectra of Y_<1-x>Ca_xVO_3:Change of electronic structures with hole doping in Mott-Hubbard insulators" Physical Review B. vol.47. (1992)

[Publications] Y.Tokura: "Fillingness dependence of electronic structures in strong correlated electron systems : titanates and vanadates" J.Phys.Chem.Solids. vol.53. 1619-1625 (1993)

[Publications] H.Sato et al.: "La_<2-x>Sr_xCuO_4(110)thin films epitaxially grown along the CuO_2plane on Pr_2CuO_4Single crystals" Applied Physics Letters. vol.61. 2470-2472 (1992)

[Publications] M.Abbate at al.: "Controlled-Valence Properties of La_<1-x>Sr_xFeO_3and La_<1-x>Sr_xMnO_3 Studied by Soft X-ray Absorption Spectroscopy" Physical Review B. vol.46. 4511-4519 (1992)

[Publications] A.Fujimori et al.: "Doping-Induced changes on the Electronic Structure of La_xsSr_<1-X>TiO_3:Limitation of the One-Electron Rigid-Band Model and the Hubbard Model" Physical Review B. vol.46. 9841-9844 (1992)

[Publications] A.Fujimori et al.: "Evolution of the Spectral Function in Mott-Hubbard Systems with d^1 configuration" Physical Review B. vol.69. 1796-1799 (1992)

[Publications] I.H.Inoue et al.: "Electronic States in Valence Fluctuating Organic Conductor (R_1,R_2,-DCNθI)_2Cu Studied by Ultraviolet Photoemission Spectroscopy" Physical Reviw B.

[Publications] M.Abbate et al.: "Soft X-Ray Absorption Spectroscopy of Valence Oxides" Journal of Electron Spectroscopy and Related Phenomena.

[Publications] A.E.Bocquet et al.: "Electronic Structure of 3d Transiton-Metal Compounds by Analysis of Metal 2p Core-Level Photoemission Spectra" Physica Review B. vol.46. 3771-3784 (1992)

[Publications] A.Fujimori: "Electronic Structure of Metallic Oxides:Band Gap Closure and Valence Control" Journal of Physics and Chemistry of Solids. vol.53. 1595-1602 (1992)

[Publications] A.Fujimori et al.: "Evolution of the Spectral Function in Mott Hubbard Systems across Metal-Insulator Transitions" Physica B.

[Publications] 藤森 淳: "X線光電子分光(XPS)および紫外線光電子分光(UPS)による高温超伝導体の研究" NSMF News. vol.33. 28-32 (1992)

秋光純青山学院大学, 理工学部, 教授 (80013522)

[Publications] 秋光純他: "新超伝導体探索研究の現状と展望" 日本結晶学会誌. vol.34. 273-282 (1992)

[Publications] 藤森淳: "X線光電子分光(XPS)および紫外線光電子分光(UPS)による高温超伝導体の研究" NSMF News. vol.33. 28-32 (1992)