Linking dynamics and kinetics of defect-doped spin chains and ladders

目前的DACH瑞士-德国方案的目标是通过结合中子能谱和热导测量来实验研究一维量子磁体的动力学和输运性质之间的关联。我们希望解决的主要问题是具有缺陷(自旋杂质)的无间隙自旋链和梯子中的激发和输运。我们将对比双链结构中的缺陷物理学(经典上，传播的磁性准粒子可以绕过缺陷)和单链结构中的缺陷物理学(其中链断裂使缺陷不可避免)。我们还计划研究缺陷诱导现象对准粒子(自旋)相互作用的符号和强度的依赖性。对于这些任务，我们选择了几个目标化合物，它们被认为是基本一维S=1/2海森堡模型的近乎理想的实现。将通过化学替代的方式引入S=0、S=1、S=3/2等类型的缺陷。非弹性中子散射实验将探索自旋缺陷对自旋激发谱的影响，重点是新的局域和束缚缺陷态。平行热输运测量将研究自旋传播的动力学方面及其与晶格声子的相互作用。最终目标将是将这些动力学和动力学研究的结果联系在一起，形成一幅物理图景。对于大多数计划中的研究途径，已经获得了诱人的和非常有希望的初步结果。DACH联合提案的主要思想是协同利用苏黎世ETH和德累斯顿IFW建立的互补专业知识。ETHZ的团队在量子磁铁的中子散射研究方面有着长期的记录，但在有机自旋系统方面也有丰富的经验。位于德累斯顿的IFW团队在磁性输运研究方面是公认的领导者，并且在低维铜氧化物方面拥有丰富的经验。这两个小组还将汇集他们的补充表征方法，包括核磁共振和高分辨率拉曼光谱(ETHZ)。

The goal of the present DACH Swiss-German proposal is to experimentally investigate the correlation between dynamical and transport properties of one dimensional quantum magnets, by combining neutron spectroscopy and thermal conductivity measurements. The main issue that we wish to address is excitations and transport in gapless spin chains and ladders with defects (spin impurities). We shall contrast defect physics in double-chain structures (where, classically, a propagating magnetic quasiparticle could bypass a defect), to that in single chains (where chain fragmentation makes defects unavoidable). We also plan to investigate the dependence of defect-induced phenomena on the sign and strength of quasiparticle (spinon) interactions. For these tasks we have selected several target compounds that are known to be almost ideal realizations of basic one dimensional S = 1/2 Heisenberg models. S = 0, S = 1, and S = 3/2 and other types of defects will be introduced by means of chemical substitution. Inelastic neutron scattering experiments will probe the effect of spin defects on the spinon excitation spectrum, with a focus on novel localized and bound defect states. Parallel heat transport measurements will investigate the kinetic aspects of spinon propagation and their interactions with lattice phonons. The ultimate goal will be to connect the findings of these dynamical and kinetic studies in a single physical picture. For most planned avenues of research, tantalizing and very promising preliminary results have already been obtained. The main idea of this DACH joint proposal is to take synergetic advantage of the complementary expertise that has been built up ETH Zurich and IFW Dresden. The group at ETHZ has a long standing record in neutron scattering studies of quantum magnets, but also substantial experience in organic spin systems. The team at IFW Dresden is a recognized leader in magnetic transport studies, and has extensive experience with low-dimensional cupric oxides. The two groups will also pool their arsenal of supplementary characterization methods, including NMR and high-resolution Raman spectroscopy (ETHZ).