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

• 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

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。特别是，我们研究了具有非零磁化强度的系统，与已广泛研究的由单线对组成的系统形成鲜明对比。我们还研究了时间相关场下系统的动力学特性。作为具体课题，我们研究了S=1系统或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 类海森堡反铁磁模型的磁化过程中量子涨落的影响，我们发现了各种场感应相。已经研究了由于自旋交叉引起的相变。我们开发了数值方法来研究相互作用自旋系统的ESR线形，并研究了正交二聚体系统线形的场向依赖性。我们还研究了纳米级磁体中磁化强度绝热变化的起源，发现 Dzyaloshinskii-Moriya 相互作用起着重要作用，但它会导致强烈的场向依赖性。作为场向自由绝热转变的机制，我们还研究了超精细相互作用的影响。量子交换的想法被提出。还研究了由于自旋涨落引起的热传导。

项目成果

K.Saito, S.Miyashita: "Enhancement of the Thermal Conductivity in Gapped Quantum Spin Chains"J.Phys.Soc.Jpn.. 71. 2485-2488 (2002)

K.Saito、S.Miyashita：“带隙量子自旋链中导热性的增强”J.Phys.Soc.Jpn.. 71. 2485-2488 (2002)

K.Saito, S.Miyashita: "Enhancement of the Thermal Conductivity in Gapped Quantum Spin Chains"J.Phys.Soc.Jpn.. 71. 2485-2488 (2002)

K.Saito、S.Miyashita：“带隙量子自旋链中导热性的增强”J.Phys.Soc.Jpn.. 71. 2485-2488 (2002)

A.Ogasahara, S.Miyashita: "Effects of Dzyaloshinsky-Moriya interaction on ESR in Shastry-sutherland model"J.Phys.Soc.Jpn.. 72. 2350-2356 (2003)

A.Ogasahara、S.Miyashita：“Dzyaloshinsky-Moriya 相互作用对 Shastry-sutherland 模型中 ESR 的影响”J.Phys.Soc.Jpn.. 72. 2350-2356 (2003)

S.Miyashita, H.de Daedt, K.Michielsen: "Directionally Independent Energy Gap Formation Due to the Hyperfine Interaction"Prog.Theor.Phys.. 111. 889-899 (2003)

S.Miyashita、H.de Daedt、K.Michielsen：“由于超精细相互作用而形成方向独立的能隙”Prog.Theor.Phys.. 111. 889-899 (2003)

N.Todoroki, S.Miyashita: "Ordered Phases and Phase Transitions in The Stacked Triangular Antiferromagnet CsCoCl3 and CsCoBr3"J.Phys.Soc.Jpn.. 73. 412-416 (2004)

N.Todoroki、S.Miyashita：“堆叠三角形反铁磁体 CsCoCl3 和 CsCoBr3 中的有序相和相变”J.Phys.Soc.Jpn.. 73. 412-416 (2004)