Impurities and disorder in nearly integrable models

近可积模型中的杂质和无序

• 批准号: 421428100
• 负责人: Dr. Imke Schneider
• 金额: --
• 依托单位: Arbeitsgruppe Grundlagen der Festkörper und Vielteilchensysteme
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/421428100?language=en
• 关键词: Impurities; disorder; nearly; integrable; models

The effects of impurities in spin-1/2 Heisenberg chains are recently experiencing a renewed interest due to experimental realizations in solid state systems and ultra-cold gases. Due to spatial confinement impurities have strong impact on the magnetic excitation spectrum and transport properties in one dimension. Already the smallest generic scatterer can block the magnetic conductance which leads to effectively isolated finite chain segments with discrete energies and characteristic boundary correlations. Surprisingly, relatively little is known about impurity effects on the momentum- and frequency resolved dynamical structure factor. A simple model based on finite chain segments predicts a pseudogap in the weak disorder limit. This must be contrasted to the strong disorder limit modelled by the random bond spin chain where a divergent low energy dynamical structure factor is predicted. Now it would be important to account for experimentally relevant thermal fluctuations, next-nearest neighbour spin couplings and magnetic properties of the impurities. In this project we aim for a full understanding of the effects of impurities on the dynamical structure factor of one-dimensional spin chains. Bonds linking the finite chain segments, other type of impurities and finite temperature will be taken into account. Eventually we will increase the disorder concentration and investigate the crossover from weak disorder to the strong disorder random singlet phase.

由于在固态系统和超冷气体中的实验实现，自旋为1/2的海森堡链中杂质的效应最近经历了新的兴趣。由于空间限制，杂质对一维磁激发谱和输运性质有很大的影响。 已经最小的通用散射体可以阻止磁导，这导致有效隔离的有限链段与离散的能量和特征边界相关性。令人惊讶的是，相对知之甚少的杂质对动量和频率分辨动力学结构因子的影响。一个简单的模型的基础上有限的链段预测的pseudogap弱无序极限。这必须与强无序极限建模的随机键自旋链，其中一个发散的低能量动力学结构因子的预测。 现在，重要的是要考虑实验相关的热波动，次近邻自旋耦合和杂质的磁性。 在这个项目中，我们的目标是充分了解杂质对一维自旋链的动力学结构因子的影响。将考虑连接有限链段的键、其他类型的杂质和有限温度。 最后，我们将增加无序浓度，并研究从弱无序到强无序随机单重态相的交叉。