Dynamical Properties of two-leg spin ladders and bond-alternating spin chaions

双腿自旋梯和键交替自旋链的动力学性质

基本信息

批准号：
14540336
负责人：
SUGA Sei-ichiro
金额：
$ 1.41万
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：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540336/
关键词：
S=1 bond-alternating spin chain dynamical structure factor transverse magnetic fields Tomonaga-Luttinger liquid NMR relaxation rate incommensurate magnetic order optical absorption spectra Kondo insulator 垂直磁揚ハルデーンギャップ数値厳密対角化動的平均場

项目摘要

(1) Dynamical properties of S=1 bond-alternating spin chains in transverse fieldsS=1 bond-alternating spin chains exhibit a quantum phase transition between the Haldane-gap phase and the dieter phase depending on the bond-alternating ratio. Recent inelastic neutron-scattering experiments revealed that typical compounds in respective phases NDMAP and NTENP show different dynamical properties in transverse magnetic fields. We have calculated dynamical structure factors of NDMAP and NTENP in transverse magnetic fields. From the analysis of field dependence of the one-magnon isolated model and the excitation continuum, we have shown that the characteristic field dependence results in the different field dependence of the excitation continuum.(2) Field-induced incommensurate state in frustrated S=1/2 bond-alternating spin chains in magnetic fieldsIn a typical S=1/2 bond alternating spin-chain compound F_5PNN, non-trivial temperature dependence of the NMR relaxation rate was observed in magn … More etic fields. We have investigated critical properties of the system in magnetic fields by introducing the next-nearest-neighbor interaction, and explained the experimental findings in viewpoint of the Tomonaga-Luttinger liquid. Furthermore, taking account of the interchain interaction by mean field theory, we have shown that the incommensurate ordered state takes place around the half-value of the magnetization saturation.(3) Optical absorption spectra in S=1/2 spin laddersOptical absorption spectra in S=1/2 two-leg spin ladders are investigated by the RVB description and the numerical diagonalization method. We have shown that the shoulder structure caused by the cyclic four spin interaction appears in addition to the ordinary two-mignon peak. On the basis of the numerical results, the frequencies for the shoulder and peak of a typical compound SrCu_2O_3 are evaluated.(4) Field induced phase transition in Kondo insulatorOn the basis of the periodic Anderson model, we have obtained the temperature field phase diagram of the Kondo insulator, combining dynamical-mean-field theory and quantum Monte Carlo technique. As field is increased in low temperatures, the phase transition among Kondo insulator-antiferromagnet-spin polarized metal occurs. Slightly above the antiferromagnetic transition temperature, heavy-fermion states with the enhanced mass are realized. Its origin was discussed in viewpoint of the one particle spectrum and the dynamical spin susceptibility. Less

(1)横向场中S=1键交替自旋链的动力学性质S=1键交替自旋链根据近期非弹性中子的比例表现出Haldane带隙相和二元相之间的量子相变。 -散射实验表明，NDMAP和NTENP各自相中的典型化合物在横向磁场中表现出不同的动力学性质，我们计算了NDMAP和NTENP在横向磁场中的动力学结构因子。通过对单磁振子孤立模型和激励连续体的场相关性的分析，我们发现特征场相关性导致了激励连续体的场相关性不同。(2)受挫S中的场致非通约态。磁场中的 =1/2 键交替自旋链在典型的 S=1/2 键交替自旋链化合物 F_5PNN 中，观察到 NMR 弛豫率的非平凡温度依赖性我们通过引入近邻相互作用研究了磁场中系统的关键特性，并从 Tomonaga-Luttinger 液体的角度解释了实验结果，此外还考虑了链间相互作用。通过平均场理论，我们证明了在磁化饱和度的半值附近出现了不相称有序态。 (3) S=1/2自旋梯中的光吸收光谱通过RVB描述和数值对角化方法研究了S=1/2二腿自旋梯，我们发现除了普通的二腿峰之外，还出现了由循环四自旋相互作用引起的肩结构。根据数值结果，评估了典型化合物SrCu_2O_3的肩峰频率和峰值频率。(4)近藤绝缘体场致相变在周期性Anderson模型的基础上，我们得到了近藤绝缘体的温度场相图。近藤绝缘体，结合动态平均场理论和蒙特量子卡罗技术，随着低温下场的增加，近藤绝缘体-反铁磁体-自旋极化金属之间发生相变，重费米子态发生在略高于反铁磁转变温度。从单粒子谱和动态自旋磁化率的角度讨论了增强质量的起源。