2005 Fiscal Year Final Research Report Summary
Theoretical Studies of Low Dimensional Quantum Magnets with Spatial Structures
| Project/Area Number |
14540350
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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 Saitama University, Faculty of Science, Professor, 理学部, 教授 (20133704)
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| Project Period (FY) |
2002 – 2005
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| Keywords | random magnet / quasiperiodic magnet / quantum kagome magnet / DMRG / quantum phase transition / ferrimagnetism / magnetization plateau / bond operator |
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| Research Abstract |
1.The quantum phase transitions due to lattice deformation and anisotropy in the S=1 kagome Heisenberg antiferromagnet are investigated. It is shown that the ground state of the undeformed isotropic system is the HSS-state proposed by the present head investigator.
2.The quantitatively accurate ground state phase diagram of the one-dimensional S=1 XXZ model is determined. Although the present result is not qualitatively new, it will serve as a standard in this field due to its quantitative accuracy.
3.The behavior of the plateau at the half of the saturation magnetization is investigated using the density matrix renormalization group method for the mixed zigzag bond Heisenberg chain and zigzag bond Heisenberg chain in which the strong bonds are randomly replaced by the ferromagnetic bonds.
4.The magnetization process of the mixture of the antiferromagnetic alternating bond chain and the uniform chain is investigated using the DMRG method. It is shown that the experimental magnetization cu
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rve obtained by Ajiro and workers is explained results.
5.The ground state of Fibonacci antiferromagnetic XXZ model is re-investigated using the real space renormalization group method in the case where the magnitudes of the two exchange interactions are largely different. The ground state phase diagram is obtained and the presence of new universality class is shown.
6.The bond operator mean field method is appled to the m=1/3 plateau state of the one-dimensional zigzag alternating bond chain to reproduce the phase diagram obtained by Tonegawa et al. The effect of the interchain interaction is also investigated.
7.Among the M=1/3 plateaus of the period-3 S=1/2 zigzag Heisenberg model, it is shown that the classical plateau state and quantum plateau state are different phases and that there exists an imtermediate phase with Z_2 symmetry breakdown. The model with 4-spin interaction with the quantum plateau ground state is also constructed.
8.The S【greater than or equal】1 Heisenberg chain with spatially modulated single ion anisotropy D is investigated by numerical diagonalization. It is shown that various antiferromagnetic phases and ferrimagnetic phases appear according to the pattern of the spatial modulation.
9.In quasi-one-dimensional quantum magnets in the magnetic field, randomness revives the spins and induces the transverse magnetic order on the one hand. On the other hand, it induces the randomness induced plateau and destroys the magnetic order. As a result of the competition of these two mechanisms, it is shown that this system undergoes multiple reentrant phase transitions with the increase of the magnetic field. Less
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Research Products
(26 results)
