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Study on mechanism and dynamical control of quantum dynamics of magnets

磁体量子动力学机理及动力学控制研究

基本信息

批准号：
14540353
负责人：
MIYASHITA Seiji
金额：
$ 2.24万
依托单位：
The University of Tokyo
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 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540353/
关键词：
quantum spin systems Nanoscale molecular magnet nonadiabatic transition ESR quantum dynamics spin crossover quantum diffusion quantum switching 量子ダイナミクススピンパイエルス相転移

项目摘要

We have studied characteristics of quantum magnets. In particular we have studied systems with non-zero magnetization in contrast to the systems consist of the singlet pairs which have been studied widely. We also studied dynamical properties of the systems under time dependent field. As concrete subjects, we studied Spin-Peierls transition in the systems with S=1 or in the quantized phonon systems. We also studied effects of quantum fluctuation in the magnetization process of S=1/2 XY-like Heisenberg antiferromagnetic models where we found various field induced phases. Phase transitions due to the spin-crossover has been studied. We have developed numerical method to study ESR line shape of interaction spin system and studied field-direction dependence of the line shape of an orthogonal-dimer system. We also studied origin of the adiabatic change of magnetization in naoscale magnets and found the Dzyaloshinskii-Moriya interaction plays an important role, but it causes strong field-direction dependence. As a mechanism of field-direction free adiabatic transition we also studied effects of hyperfine interaction. The idea of quantum switching has been proposed. Heat conduction due to spin fluctuation has been also studied.

我们研究了量子磁体的特性。特别地，我们研究了非零磁化的系统，而不是广泛研究的由单线态对组成的系统。研究了系统在时间场作用下的动力学性质。作为具体的研究对象，我们研究了S=1系统和量子化声子系统中的自旋-佩尔斯跃迁。我们还研究了S=1/2 xy类Heisenberg反铁磁模型磁化过程中量子涨落的影响，发现了不同的场诱导相。研究了自旋交叉引起的相变。我们建立了研究相互作用自旋体系ESR线形的数值方法，并研究了正交二聚体体系线形与场方向的关系。我们还研究了纳米级磁体的绝热磁化变化的起源，发现Dzyaloshinskii-Moriya相互作用起着重要的作用，但它引起了很强的场方向依赖性。作为场向自由绝热跃迁的机制，我们还研究了超细相互作用的影响。量子交换的思想已经被提出。对自旋涨落引起的热传导也进行了研究。