New Developments in the Theory of Non-Magnetic Ground State and Magnetic-Field-Induced Spin Gap in Low Dimensional Spin Systems

低维自旋系统非磁基态和磁场诱导自旋间隙理论的新进展

基本信息

批准号：
14540329
负责人：
OKAMOTO Kiyomi
金额：
$ 2.3万
依托单位：
Tokyo Institute of Technology
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

By use of analytical and numerical methods, we have investigated the ground states with zero or finite magnetic fields for various one-dimensional and quasi-one-dimensional spin systems. Especially, we have focused on the spin-gap states in zero or finite magnetic fields.1. We have proposed several mechanisms for the magnetic-filed-induced spin gap at 1/4 of the saturation magnetization of a ladder type organic spin system BIP-TENO. We have succeeded to explain the behavior of the observed magnetization curve.2. We have studied the distorted diamond type spin chain, by use of analytical and numerical methods, especially focusing on the ground states in zero and finite magnetic field. In this system, there appears various phases depending upon the quantum parameters. In particular, it was found the change in the mechanism for the magnetization plateau at 1/3 of the saturation magnetization. The magnetic properties of azurite are well described by this model.3. We have obtained the definitive conclusion on the phase diagram of the spin ladder with the bond alternation.4. We have found the inversion phenomenon between the anisotropies of the Hamiltonian and the wave function for the spin systems with three keywords : trimer nature, frustration and the XXZ anisotropy of the spin-spin interactions. Namely, in some regions of the quantum parameters, the Neel ground state is realized in spite of the fact that the interactions is XY-like. And also, the spin-fluid ground state is realized when the interaction is Ising-like.5. We have clarified the condition for the appearance of the spin orderng which is incommensurate to the lattice for the material F5PNN.

通过使用分析方法和数值方法，我们研究了各种一维和准二维自旋系统的基态或有限磁场的基态。特别是，我们专注于零或有限磁场的自旋隙状态1。我们已经提出了几种机制，用于在梯子型有机旋转系统Bip-teno的饱和磁化的1/4处进行磁性伪造的自旋隙。我们成功地解释了观察到的磁化曲线的行为。2。我们通过使用分析方法和数值方法研究了扭曲的钻石型自旋链，尤其是以零和有限磁场为重点。在此系统中，根据量子参数的不同阶段。特别是，发现在饱和磁化的1/3处的磁化高原机理的变化。该模型很好地描述了Azurite的磁性3。我们已经通过键交替获得了自旋梯的相图的确定性结论。4。我们已经发现，哈密顿量各向异性与带有三个关键字的自旋系统的波函数之间的反转现象：旋转性质，挫败感和自旋旋转相互作用的XXZ各向异性。也就是说，在量子参数的某些区域中，尽管相互作用类似于xy，但neel基态还是实现的。而且，当相互作用类似于5时，可以实现自旋流体基态。5。我们已经阐明了Spin Orderng出现的条件，该条件与材料F5PNN的晶格不相关。