Theoretical Studies of Low Dimensional Quantum Magnets with Spatial Structures

具有空间结构的低维量子磁体的理论研究

基本信息

批准号：
14540350
负责人：
HIDA Kazuo
金额：
$ 2.3万
依托单位：
Saitama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

项目摘要

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 … More 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

1.研究了由于晶格变形而引起的量子相变，S = 1 kagome Heisenberg抗fiferromagnet。结果表明，未呈现的各向同性系统的基态是本主管研究者提出的HSS状态。2。确定一维s = 1 xxz模型的定量准确的基态相位图，尽管目前的结果既不是在定性上是新的，但由于其定量精确的标准，因此它将作为量化量的标准化。混合Zigzag Bond Heisenberg链和Zigzag Bond Heisenberg链的密度矩阵重新归一化组方法，其中强键被铁磁键随机替换。结果表明，Ajiro和工人获得的实验性磁化cu…被解释了结果。5。斐波那契抗磁性XXZ模型的基态在使用实际空间重量化组方法的情况下重新投资了两种交换相互作用的磁场，在很大程度上是不同的。获得了基态相图并显示了新的普遍性类别的存在。6。键合算子平均场方法被添加到一维曲折替代键链的M = 1/3高原状态，以重现Tonegawa等人获得的相图。还研究了链相互作用的效果。7.在周期3 s = 1/2 sigzag heisenberg模型的M = 1/3高原，这表明经典的高原状态和量子高原状态是不同的阶段，并且存在Z_2对称击球的IMTERMETIADE相。还构建了与量子平原基态相互作用的4旋相互作用的模型。8。通过数值对角度化研究了具有空间调制的单离子各向异性D的Heisenberg链，其具有空间调制的单离子各向异性D。结果表明，根据空间调制的模式出现了各种抗铁磁相和铁磁相。9.IN磁场中的准二维量子磁体，随机性恢复了旋转并诱导横向磁性序列。另一方面，它诱导了随机性引起的平稳性并破坏了磁性。由于这两种机制的竞争，这表明该系统随着磁场的增加而经历了多个恢复相变。较少的