Behavior of a magnetic impurity in small metallic systems

小型金属系统中磁性杂质的行为

基本信息

批准号：
10640344
负责人：
SUGA Seiichiro
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640344/
关键词：
Kondo effect Anderson localization S=1 2 gapped spin chain Tomonaga-Luttinger liquid NMR critical property dynamical structure factor magnetization plateau 量子モンテカルロ近藤温度非フェルミ流体 S=1 素励起スペクトルベーテ仮説磁場 NMR緩和率ギャップを持つ1次元量子スピ

项目摘要

Results of the present project are summarized as follows :1. We investigated the Kondo effect in two-dimensional disordered systems using a quantum Monte Carlo method. It was shown that the local magnetic moment is screened or unscreened by the spin of the conduction electron, depending on the position of a magnetic impurity. The correlation function between the local moment and the spin of the conduction electron was also calculated. Even when the local moment is completely screened, the ferromagnetic correlation in the vicinity of the local moment is suppressed due to randomness. When the screening is incomplete, the antiferromagnetic correlation in the vicinity of the local moment is strongly suppressed.2. The elementary excitation spectrums for the Anderson model and the orbitally degenerate Anderson model were investigated at finite temperatures using the Bethe ansatz solution. We calculated a crossover behavior of the elementary excitation spectrums between the mixedvalence regim … More e and the Kondo regime. We also calculated the elementary excitation spectrums in crystalline fields such as tetragonal field and cubic field. Results were discussed in connection with thermodynamic quantities.3. Critical properties of various one-dimensional spin-gapped systems in magnetic fields were investigated systematically by combining a numerical diagonalization method and finite-size-scaling analysis based on conformal field theory. We calculated magnetic-field dependence of the critical exponent of the spin correlation function. Using the numerical results, we discussed the experimental findings concerning the NMR relaxation rates of the S=1/2 two-leg ladder material and the Haldane-gap material in magnetic fields.4. Using the continued fraction method based on Lanczos algorithm, the dynamical structure factor of the S=1/2 bond-alternating chain with a next-nearest-neighbor interaction was calculated at the magnetization-plateau region. Results were discussed in comparison with the exact excitation spectrums of an effective Hamiltonian ; one-dimensional S=1/2XXZ model. Less

本项目的结果总结如下：1.我们使用量子蒙特卡罗方法研究了二维无序系统中的近藤效应，结果表明局部磁矩受到传导电子自旋的屏蔽或未屏蔽。还计算了局部矩与传导电子自旋之间的相关函数，即使局部矩被完全屏蔽，局部矩附近的铁磁相关性也会被抑制。当筛选不完全时，局部矩附近的反铁磁相关性被强烈抑制。2．利用Bethe ansatz解在有限温度下研究了Anderson模型和轨道简并Anderson模型的基本激发谱。我们计算了混合价态和近藤态之间的基本激发光谱的交叉行为，我们还计算了四方场和立方场等晶体场中的基本激发光谱。 3.结合数值对角化方法和基于共形场理论的有限尺寸尺度分析，研究了磁场中各种一维自旋间隙系统的临界性质。自旋相关函数临界指数的场依赖性，我们讨论了有关 S=1/2 两腿材料梯和 Haldane 能隙材料在磁场中的 NMR 弛豫率的实验结果。4 .使用基于Lanczos算法的连分数法，计算了具有次近邻相互作用的S=1/2键交替链在磁化平台区域的动力学结构因子，并与精确的激发谱进行了比较。有效哈密顿量；一维 S=1/2XXZ 模型。