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f-電子系におけるスピンと軌道揺らぎの競合と協調に関する研究

Research Project

Project/Area Number14740219
Research Category

Grant-in-Aid for Young Scientists (B)

Allocation TypeSingle-year Grants
Research Field 固体物性II(磁性・金属・低温)
Research InstitutionJapan Atomic Energy Agency

Principal Investigator

堀田 貴嗣  特殊法人日本原子力研究所, 先端基礎研究センター, 副主任研究員 (00262163)

Project Period (FY) 2002 – 2004
Project Status Completed(Fiscal Year 2004)
Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 2004 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2003 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 2002 : ¥2,200,000 (Direct Cost : ¥2,200,000)
Keywordsf電子 / 電子相関 / 超伝導 / 磁性 / 軌道自由度 / スピン自由度 / バンド計算 / 結晶場 / f-電子
Research Abstract

相対論的バンド計算手法を用いて、アメリシウム系化合物AmCoGa_5のフェルミ面構造を明らかにした。得られたフェルミ面は、複数の大きな円筒状電子面と小さなホール面から成るが、PuCoGa_5のそれと形状が良く似ている。超伝導体であるPuCoGa_5とi類似の2次元的フェルミ面の存在は、AmCoGa_5も超伝導になる可能性を示唆している。これまでに、j-j結合描像に基づいてf電子系に対する軌道縮退ババード模;型を構築する一般的な方法を開発してきたが、今年度はその方法を用いてネプツニウム化合物の理論模型を構築した。まず、二酸化ネプツニウムNpO_2の25K以下に現れる秩序状態を明らかにするために、面心立方格子上で軌道縮退模型を解析した。その結果、4方向の八極子モーメントが配列した構造が基底状態となることを見出した。これにより、1953年に発見され、半世紀にわたって謎のままであったNpO_2の基底状態の正体が八極子秩序であることを微視的観点から解明することに成功した。また、正方晶の格子上で理論模型を解析し、ネプツニウム化合物NpTGa5の磁気構造が遷移金属原子Tによって変化する様相を明らかにした。さらに、充填スクッテルダィト化合物PrOs_4Sb_12の磁性および超伝導機構を解明するために、軌道縮退アンダーソン模型を数値繰り込み群法によって解析した。その結果、基底状態が非磁性の一重項でも、わずかな励起エネルギーで磁気的な三重項が存在していれば磁気揺らぎが低温まで生き残り、この磁気揺らぎによって異方的非BCS超伝導が現れる可能性を指摘した。

Report

(3results)
  • 2004 Annual Research Report
  • 2003 Annual Research Report
  • 2002 Annual Research Report

Research Products

(18results)

All 2005 2004 Other

All Journal Article Publications

  • [Journal Article] Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure2005

    • Author(s)
      Takashi Hotta
    • Journal Title

      Journal of the Physical Society of Japan 74・4(印刷中)

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Magnetic Fluctuations of Filled Skutterudites Emerging in the Transition Region between Singlet and Triplet States2005

    • Author(s)
      Takashi Hotta
    • Journal Title

      Physical Review Letters 94・6

      Pages : 67003-67003

    • Related Report
      2004 Annual Research Report
  • [Journal Article] An Orbital-based Scenario for Magnetic Structure of Neptunium Compounds2004

    • Author(s)
      Hiroaki Onishi, Takashi Hotta
    • Journal Title

      New Journal of Physics 6・1

      Pages : 193-193

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Orbital-Controlled Magnetic Transition between Gapful and Gapless Phases in the Haldane System with t2g Orbital Degeneracy2004

    • Author(s)
      Hiroaki Onishi, Takashi Hotta
    • Journal Title

      Physical Review B 70・10

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Spin and orbital structure of uranium compounds on the basis of a j-j coupling scheme2004

    • Author(s)
      Takashi Hotta
    • Journal Title

      Physical Review B 70・5

      Pages : 54405-54405

    • Related Report
      2004 Annual Research Report
  • [Journal Article] Orbital Ordering, New Phases, and Stripe Formation in Layered Nick elates2004

    • Author(s)
      Takashi Hotta, Elbio Dagotto
    • Journal Title

      Physical Review Letters 92・22

      Pages : 227201-227201

    • Related Report
      2004 Annual Research Report
  • [Publications] T.Hotta: "Spin and orbital structure of uranium compounds on the basis of a j-j coupling scheme"Physical Review B. (発表予定).

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Hotta, K.Ueda: "Microscopic approach to exotic superconductivity in f-electron systems"Journal of Magnetism and Magnetic Materials. (印刷中).

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Hotta, K.Ueda: "Odd-Parity Triplet Pair Induced by Hund's Rule Coupling"Physical Review Letters. 92(No.10). 107007 (2004)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Takimoto, T.Hotta, K.Ueda: "Strong-coupling theory of superconductivity in a degenerate Hubbard model"Physical Review B. 69(No.10). 104504 (2004)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Maehira, T.Hotta, K.Ueda, A.Hasegawa: "Electronic Structure and the Fermi Surfaces of PuCoGa_5 and NpCoCa_5"Physical Review Letters. 90(No.20). 207007 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Takimoto, T.Hotta, K.Ueda: "Superconductivity in the Orbital Degenerate Model for Heavy Fermion Systems"Journal of Physics : Condensed Matter. 15(No.28). 2087-2093 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] T.Maehira, T.Hotta, K.Ueda, A.Hasegawa: "Electronic Structure and Fermi Surface of AnCoGa_5 (An=Np and Pu)"Physical Review Letters. (発表予定).

    • Related Report
      2002 Annual Research Report
  • [Publications] T.Hotta, K.Ueda: "Construction of a microscopic model for f-electron systems based on a j-j coupling scheme"Physical Review B. (発表予定).

    • Related Report
      2002 Annual Research Report
  • [Publications] T.Maehira, T.Hotta, K.Ueda, A.Hasegawa: "Relativistic Band-Structure Calculations for CeTIn5 (T=Ir and Co) and Analysis of the Energy Bands by Using Tight-Binding Method"Journal of the Physical Society of Japan. (発表予定).

    • Related Report
      2002 Annual Research Report
  • [Publications] T.Hotta, K.Ueda: "Effect of orbital degeneracy on triplet superconductivity in f-electron systems"Acta Physica Polonica B. 34(No.2). 443-446 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] T.Maehira, T.Hotta, T.Takimoto, K.Ueda, A.Hasegawa: "Tight-Binding Model for Heavy Fermion Compounds : Cnostruction of f-p model"Acta Physica Polonica B. 34(No.2). 1023-1026 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] T.Takimoto, T.Hotta, T.Maehira, K.Ueda: "Spin Fluctuation Induced Superconductivity Controlled by Orbital Fluctuations"Journal of Physics : Condensed Matter. 14(No.21). L369-L375 (2002)

    • Related Report
      2002 Annual Research Report

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Published : 2002-04-01   Modified : 2016-04-21  

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