| Project/Area Number |
11694074
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SIGRIST Manfred W. Kyoto University, Yukawa Institute for Theoretical Physics, Professor, 基礎物理学研究所, 教授 (60293966)
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| Co-Investigator(Kenkyū-buntansha) |
TSUNETSUGU Hirokazu Tsukuba University, Institute for Materials Science, Associate Professor, 物質工学系, 助教授 (80197748)
KAWAKAMI Norio Osaka University, Applied Physics, Professor, 大学院・工学研究科, 教授 (10169683)
UEDA Kazuo University of Tokyo, Institute for Solid State Physics, Professor, 物性研究所, 教授 (70114395)
FURUKAWA Nobuo Aoyama Gakuin University, Department of Physics, Associate Professor, 理工学部, 助教授 (00238669)
FURUSAKI Akira Kyoto University, Yukawa Institute for Theoretical Physics, Associate Professor, 基礎物理学研究所, 助教授 (10238678)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2000: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1999: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Quantum phase transition / Strongly correlated electron system / Magnetism / Spin gap / Random spin system / Kondo lattice / Unconventional superconductivity / Non-magnetic impurity |
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| Research Abstract |
The exact ground state and the excitation spectrum of the Shastry-Sutherland spin system, and the presence of magnetization plateaus and their properties have been analyzed. Furthermore the possible quantum phase transition within this model has been studied. This problem applies to SrCu_2(BO_3)_2, which is a system close to a quantum critical point.
The elimination of the quantum phase transitions due to impurity effects in two-dimensional plaquette RVB systems was analyzed by means of stochastic series expansion.
Quantum phase transition in systems with dimerized, plaquette or mixed spin structures : the conditions for the transition between a valence-bond solid and various magnetically ordered plases have been analyzed for various cases.
The low-energy properties of the SU(4)-symmetric Kugel-Khomskii chain with spin and orbital (isospin) degrees of freedom have been studied analytically from symmetry point of view and numerically. The multi-orbital effects have been investigated for Ca-doped Sr_2RuO_4 based on localized spin and orbital degrees of freedom which occur in an orbital-dependent Mott-transition.
The ground state and low-energy properties of the (geometrically frustrated) pyrochlore systems with spin-1/2 and spin-1 degrees af freedom have been studied, in view of the quantum phase transition driven by large residual entropy, including Jahn-Teller type of deformations.
The Luttinger liquid behavior was investigated in the doped Kondo lattice model, where a new small energy scale appears.
The relation between magnetic correlation and the unconventional superconductivity was studied for the case of the spin-triplet superconductor Sr_2RuO_4.
Properties of the low-energy quasiparticle density of states and localization effects in quantum wires and coupled chains with off-diagonal disorder have been classified.
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