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Calculation of Raman Spectra in Quantum Antiferromagnetic Systems containing Spin Gaps

包含自旋间隙的量子反铁磁系统中拉曼光谱的计算

基本信息

批准号：
15540362
负责人：
NATSUME Yuhei
金额：
$ 2.3万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

The quantum effects have a tendency of being hidden in the shadow of classic natures. However, we can find directly quantum effects in antiferromagnetic materials, because the exchange interaction between spins plays an essential role to making quantum natures. Recently, much attention has been paid to "quantum antiferromagnetism" in the low-dimensional systems, for example layer type crystals of Transition-metal oxide compounds. In those systems, ground states are made by singlet dimers. This states have essentially energy gaps, which are called "spin gaps". In order to detect these spin gaps, the experiments of the non-elastic light-scattering process called "magnetic Raman spectrum" are quite influential.This research makes the theoretical calculation for the optical properties originating from magnetic excitations in antiferromagnetic materials. In particular, we make the exact diagonalization in the spin systems for finite numbers. This calculation gives eigenvalues and eigenvectr … More os numerically, which have quite fruitful information in characteristic features of quantum antiferromagnetic systems. In fact, we make the reproduction of Raman spectrum in calculation. Further, spatial correlation functions during spins are obtained numerically. The results suggest us the possibility of new magnetic phases in those systems. Moreover, this research is related closely to Jahn-Teller effect as the problem which concerns the basic mechanism giving the manifestation of the magnetism. Therefore, we examine the relationship between Jahn-Teller effect and the optical spectrum for those quantum antiferromagnetc compounds. In the extension process of the research, we get the viewpoint of the effect caused by "the quantum chaos", which appears in the magnetic g factor. This leads us one of the quite realistic models of "quantum chaos", as well as the new clue to investigations of magnetism. In addition, the developing of the recent experimental research for Bose-condensations in atomic gases gives us the new model which is common to such the quantum-condensed systems. Therefore, we attack actively the problem of Bose-condensations in atomic gases in relation with the process of the occurrence "quantum chaos" in Jahn-Teller effect. Less

量子效应有一种隐藏在经典自然的阴影下的趋势。然而，我们可以在反铁磁材料中直接发现量子效应，因为自旋之间的交换相互作用对产生量子性质起着至关重要的作用。近年来，在低维体系中的“量子反铁磁性”引起了人们的广泛关注，例如过渡金属氧化物化合物的层状晶体。在这些系统中，基态是由单重态二聚体形成的。这种状态本质上有能隙，也就是所谓的“自旋能隙”。为了探测这些自旋能隙，被称为磁拉曼光谱的非弹性光散射过程的实验是相当有影响的。本研究对反铁磁材料中磁激发产生的光学性质进行了理论计算。特别地，我们对有限个自旋系统进行了精确对角化。这种计算给出了特征值和特征向量…更多的数值计算结果，为量子反铁磁系统的特征研究提供了丰富的信息。实际上，我们在计算中重现了拉曼光谱。进一步，通过数值计算得到了旋转过程中的空间相关函数。这些结果表明，在这些系统中存在新磁相的可能性。此外，本研究还与Jahn-Teller效应密切相关，因为Jahn-Teller效应关系到磁性产生的基本机制。因此，我们研究了这些量子反铁磁化合物的Jahn-Teller效应与光谱之间的关系。在研究的扩展过程中，我们得到了出现在磁g因子中的“量子混沌”效应的观点。这给我们带来了一个非常现实的“量子混沌”模型，也为磁学的研究提供了新的线索。此外，最近对原子气体中玻色凝聚的实验研究的发展为我们提供了这种量子凝聚系统所共有的新模型。因此，我们结合Jahn-Teller效应中“量子混沌”的产生过程，对原子气体中的玻色凝聚问题进行了积极的研究。较少