| Project/Area Number |
11640366
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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 |
物性一般(含基礎論)
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| Research Institution | Saitama University |
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Principal Investigator |
HIDA Kazuo Faculty of Science, Professor, 理学部, 教授 (20133704)
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| Project Period (FY) |
1999 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | random magnet / quasiperiodic magnet / kagome magnet / DMRG / quantum phase transition / magnetization plateau / series expansion / numerical diagonalization / ハバードモデル / 長周期磁性体 / レベルスペクトロスコピー / 磁化ブラトー |
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| Research Abstract |
1. One-dimensional random quantum magnets
Using the density matrix renormalization group (DMRG) method, we have shown that the Haldane state in spin-1 1-dimensional Heisenterg antiferromagnet is stable against randomness.
2. One-dimensional quasiperiodic quantum magnets
Using DMRG, the ground state of spin-1/2 1-dimensional quasipenodic antiferromagnetic XXZ model is investigated. It is shown that the Fibonacci modulation, which is critical in the XY model, becomes relevant in the presence of the antiferromagnetic Ising interaction and the low energy behavior is modified drastically.
The one-dimensional half-filled Fibonacci Hubbard model is investigated using DMRG and perturbational renormalization group method. It is shown that a varity of ground states are realized even in the half-filled case. Experimental observation of these phases is expected using the quantum dot array and other systems. Our results suggest the importance of the strong correlation effect in quasiperiodic systems.
3.
… More
One-dimensional quantum magnets with long spatial periodicity
Using the exact diagonalization method, the ground state and magnetization process of various one-dimensional quantum magnets with long spatial periodicity are investigated and universality class and critical exponents of quantum phase transition are clarified.
4. Kagome lattice quantum antiferromagnet
Ground state and low energy exciatation spectrum of the spin-1 kagomee antiferromagnet which is realized in an organic material are investigated by the exact diagonalization and cluster expansion method. It is shown that both magnetic and non-magnetic excitations have finite energy gaps. The hexagonal singlet solid picture is proposed in which the frustration is fully compensated by quantum fluctuation. It is also shown that a magnetization plateau appears at 1/3 of full magnetization.
Future projects
The project with the same subject is approved and the following investigations are in progress.
(1) Magnetization process of random one-dimensional quantum magnets
(2) Finite temperature properties of the kagome antiferromagnets
(3) Ground state phase diagram of S=1 1-dimensional XXZ model with single-site anisotropy
(4) Studies of magnetization plateaux in quasi-1-dimensional and quasi-2-dinensional quantum magnets using the bond operator method Less
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