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Dynamical theory for fluctuations and phase transitions in orbitally degenerate electron systems

Research Project

Project/Area Number 10640327
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅱ(磁性・金属・低温)
Research InstitutionTohoku University

Principal Investigator

KURAMOTO Yoshio  Graduate School of Science, Tohoku University, Professor, 大学院・理学研究科, 教授 (70111250)

Co-Investigator(Kenkyū-buntansha) KUSUNOSE Hiroaki  Graduate School of Science, Tohoku University, Research Associate, 大学院・理学研究科, 助手 (00292201)
Project Period (FY) 1998 – 2000
Project Status Completed (Fiscal Year 2000)
Budget Amount *help
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywordsorbital degeneracy / quadrupole order / fluctuation / effective medium theory / elastic constants / スフェリカル・モデル / 揺らぎ / 四種極秩序 / 近藤効果 / 繰り込み / 非フェルミ液体 / CeB_6 / 無限次元
Research Abstract

Formulation of theoretical framework with account of orbital fluctuations We extended the mean-field theory to take account of fluctuation effects. The new theory becomes exact in the limit of infinite spatial dimensions, and is regarded as a quantummechanical extension of the spherical model approximation for classical spins. Our theory goes one step beyond the other ones that use localized fermions to represent spins.
Explanation of the strange order in orbitally degenerate electron systems such as CeB_6 and Ce_<0.75>La_<0.25>B_6
We explained origin of strange magnetic order in the phase III of CeB_6 by assuming a pseudo-dipolar interaction between next-nearest-neighbor sites. Furthermore, we discussed possibility of an octupole order for the newly found phase IV in Ce_<0.75>La_<0.25>B_6. We found a new plase which lies energetically close to the already observed phases, and which may be realized in the presence of external field such as uniaxial pressure. We developed new functional i … More ntegral formalism to perform the Ginzburg-Landau expansion microscopically.
Spin and orbital wave excitations in orbitally degenerate electron systems
We derived the dispersion relations of elementary excitations from the complicated spinorbital ordered state. The large unit cell with 16 Ce ions give rise to 48 branches. We derived all branches and found characteristic relation between the spectrum and the multipolar interaction. In particular some branches are almost flat along certain directions of wave vector, which may be checked by neutron diffraction.
Exact dynamics of orbitally degenerate one-dimensional systems
So far we explained results for three-dimensional systems. In low dimensions, the role of fluctuations is much more important. In order to see the situation most clearly, we studied an exactly soluble model in one dimension. This model has the SU (4) symmetry to represent the degeneracy, and the interaction is inversely proportional to the square of the distance (1/γ^2). We succeeded in deriving the dynamical correlation function exactly. Less

Report

(4 results)
  • 2000 Annual Research Report   Final Research Report Summary
  • 1999 Annual Research Report
  • 1998 Annual Research Report
  • Research Products

    (31 results)

All Other

All Publications (31 results)

  • [Publications] H.Kusunose and Y.Kuramoto: "Multipolar Kondo effect in orbitally degenerate f-electron systems"Physica B : Condensed Matter. 281-282. 544-545 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] N.Fukushima,T.Kuromaru,H.Kusunose and Y.Kuramoto: "Theory of magneto-elastic properties of interacting multipoles"Physica B : Condensed Matter. 281-282. 538-539 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] S.Watanabe and Y.Kuramoto: "Ground state and elementary excitations in the one-dimensional f^2 Kondo lattice model"Physica B : Condensed Matter. 281-282. 260-261 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] M.Arikawa,Y.Saiga,T.Yamamoto and Y.Kuramoto: "Exact dynamics in the Haldane-Shastry spin chain model in magnetic field"Physica B : Condensed Matter. 281-282. 823-824 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] S.Suzuki and Y.Kuramoto: "Transition between compressible and incompressible states in infinite-layer fractional quantum Hall systems"Phys.Rev.B. 62. 1921-1928 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Y.Saiga and Y.Kuramoto: "Dynamical properties of the 1/r^2-type supersymmetric t-J model in a magnetic field : Manifestation of spin-charge separation"J.Phys.Soc.Jpn.. 69. 3917-3931 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] H.Kusunose and Y.Kuramoto: "Multipolar Kondo effect in orbitally degenerate f-electron systems"Physica B : Condensed Matter. 281-282. 544-545 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] N.Fukushima, T.Kuromaru, H.Kusunose and Y.Kuramoto: "Theory of magneto-elastic properties of interacting multipoles"Physica B : Condensed Matter. 281-282. 538-539 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] S.Watanabe and Y.Kuramoto: "Ground state and elementary excitations in the one-dimensional f^2 Kondo lattice model"Physica B : Condensed Matter. 281-282. 260-261 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] M.Arikawa, Y.Saiga, T.Yamamoto and Y.Kuramoto: "Exact dynamics in the Haldane-Shastry spin chain model in magnetic field"Physica B : Condensed Matter. 281-282. 823-824 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] S.Suzuki and Y.Kuramoto: "Transition between compressible and incompressible states in infinite-layer fractional quantum Hall systems"Phys.Rev.B. 62. 1921-1928 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Y.Saiga and Y.Kuramoto: "Dynamical properties of the 1/γ^2-type supersymmetric t-J model in a magnetic field : Manifestation of spin-charge separation"J.Phys.Soc.Jpn. 69. 3917-3931 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] H.Kusunose and Y.Kuramoto: "Multipolar Kondo effect in orbitally degenerate f-electron systems"Physica B : Condensed Matter. 281-282. 544-545 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] N.Fukushima,T.Kuromaru,H.Kusunose and Y.Kuramoto: "Theory of magneto-elastic properties of interacting multipoles"Physica B : Condensed Matter. 281-282. 538-539 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] S.Watanabe and Y.Kuramoto: "Ground state and elementary excitations in the one-dimensional f^2 Kondo lattice model"Physica B : Condensed Matter. 281-282. 260-261 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] M.Arikawa,Y.Saiga,T.Yamamoto and Y.Kuramoto: "Exact dynamics in the Haldane-Shastry spin chain model in magnetic field"Physica B : Condensed Matter. 281-282. 823-824 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] S.Suzuki and Y.Kuramoto: "Transition between compressible and incompressible states in infinite-layer fractional quantum Hall systems"Phys.Rev.B. 62. 1921-1928 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] Y.Saiga and Y.Kuramoto: "Dynamical properties of the 1/r^2-type supersymmetric t-J model in a magnetic field : Manifestation of spin-charge separation"J.Phys.Soc.Jpn.. 69. 3917-3931 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] S.Watanabe,Y.Kuramoto,T.Nishino and N.Shibata: "Spin, charge and quasi-particle gaps in the one-dimensional Kondo lattics with f^2 configuration"J. Phys. Soc. Jpn.. 68. 159-165 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] H.Kusunose and Y.Kuramoto: "Orbital Kondo effect in Ce_xLa_<1-x>B_6 : scaling analysis,"Phys. Rev. B. 59. 1902-1991 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Y.Saiga and Y.Kuramoto: "Dynamical properties of the one-dimensional supersymmetric t-J model : a view from elementary excitations"J. Phys. Soc. Jpn.. 68. 3631-3642 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] H.Kusunose and Y.Kuramoto: "Crossover between Fermi liquid and non-Fermi liquid in orbitally degenerate Kondo systems"J. Phys. Soc. Jpn.. 68. 3960-3965 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Takashi Yamamoto,Yasuhiro Saiga,Mitsuhiro Arikawa and Yoshio Kuramoto: "Exact dynamical structure factor of the degenerate Haldane-Shastry model"Phys. Rev. Lett. 84. 1308-1311 (2000)

    • Related Report
      1999 Annual Research Report
  • [Publications] Y.Kuramoto and H.Kusunose: "Octupole Moment as a Hidden Order Paramater in Orbitally Degenerate f-Electron Systems"J. Phys. Soc. Jpn.. 69. 671-674 (2000)

    • Related Report
      1999 Annual Research Report
  • [Publications] Y.Kuramoto and Y.Kitaoka: "Dynamics of heavy electrons,"Oxford University Press (2000),. 239 (2000)

    • Related Report
      1999 Annual Research Report
  • [Publications] Y.Saiga: "Dynamical structure factors of the spin-1/2 XXZ chain with inverse-square exchange and Ising anisotropy" J. Phys. Soc. Jpn.67. 1319-1331 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] N.Fukushima: "Effects of a magnetic field on fluctuation of the quadrupolar ordering-application to the phase diagram of CeB_6-" J. Phys. Soc. Jpn.67. 2460-2468 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Y.Kuramoto: "Perturbative renormalization of multi-channel Kondo-type models," European J. Phys. B. 5. 457-464 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] H.Kusunose: "Orbital Kondo effect in Ce_xLa_<1-x>B_6 : scaling analysis," Phys. Rev. B. 59. 1902-1911 (1999)

    • Related Report
      1998 Annual Research Report
  • [Publications] 倉本義夫: "f電子系をめぐる新しい潮流" 固体物理. 33. 237-250 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] S.Watanabe: "Spin, charge and quasi-particle gaps in the one-dimensional Kondo lattice with f^2 configuration," J. Phys. Soc. Jpn.68. 159-165 (1999)

    • Related Report
      1998 Annual Research Report

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Published: 1998-04-01   Modified: 2020-05-15  

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