Spin Dynamics of Exotic Quantum Magnets

奇异量子磁体的自旋动力学

• 批准号: 229087838
• 负责人: Professor Stefan Wessel, Ph.D.
• 金额: --
• 依托单位: Institut für Theoretische Festkörperphysik C
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/229087838?language=en
• 关键词: Spin; Dynamics; Exotic; Quantum; Magnets

Quantum spin systems are an active, interesting area of current research on strongly-correlated quantum many-body systems, in particular as they provide an often well-defined platform to explore novel states of condensed matter, their corresponding excitations as well as quantum phase transitions that bound these phases to more conventional, magnetically ordered regions. Systems of interest include those that exhibit, e.g., quantum spin liquids, quantumdisorderedphases, or spin nematic states. Furthermore, with refined experimental techniques, such as provided by neutron, light or x-ray scattering probes, it has become feasible to explore in addition to their thermodynamic properties also details of the excitations that emerge in such systems. The central goal of project P6 is to employ Quantum Monte Carlo methods to provide reliable data for dynamical Response functions for a wide range of quantum spin model systems that exhibit unconventional magnetic properties. In contrast to other numerical methods, which extract such dynamical information from the real-time dynamics, within quantum Monte Carlo simulations, Equilibrium dynamical properties are accessible by measuring imaginary timedisplaced correlation functions. In order to extract from the Quantum Monte Carlo data the dynamical spectral function, an analytic continuation from the imaginary-time data to real frequencies is thus required. In the first grant period, we implemented and extended thealgorithms to perform the spin dynamical measurements as well as the analytic continuation schemes. Furthermore, we already applied our methods to different two-dimensional spin systems. For the second grant period, we now plan to focus our quantum Monte Carlo simulations to calculate spectral functions that are relevant for scattering probes such as resonant inelastic x-ray scattering (RIXS) or infrared absorption spectroscopy. We plan in particular to considerspin chain and variable-width spin ladder systems, as well as twodimensional magnetically ordered systems and sign-problem-free models of spin liquid phases. These studies will allow us to explore in detail the emergence of e.g. magnon-bound states in such Systems and provide unbiased reference data for advanced spectral probes of basic quantum magnetic model systems. Furthermore, we aim at extending our refined spectral probes to also explore the entanglement properties of quantum spin systems, based on recent advances in the numerical determination of the spectral properties of quantum-many-body entanglement Hamiltonians, where we can studyboth quantum critical points and unconventionally ordered and quantum disordered systems.

量子自旋系统是当前强关联量子多体系统研究的一个活跃而有趣的领域，特别是因为它们提供了一个通常定义良好的平台来探索凝聚态的新状态，它们相应的激发以及将这些相绑定到更传统的磁有序区域的量子相变。感兴趣的系统包括那些表现出，例如，量子自旋液体，量子无序相，或自旋态。此外，随着完善的实验技术，如中子，光或X射线散射探针提供的，它已成为可行的探索，除了他们的热力学性质也出现在这样的系统中的激发的细节。项目P6的中心目标是采用量子蒙特卡罗方法为表现出非常规磁性的各种量子自旋模型系统的动态响应函数提供可靠的数据。与从实时动态中提取这种动态信息的其他数值方法相比，在量子蒙特卡罗模拟中，可以通过测量虚时间位移相关函数来获得平衡动力学特性。为了从量子蒙特卡罗数据中提取动力学谱函数，因此需要从虚时数据到真实的频率的解析延拓。在第一个资助期，我们实现并扩展了自旋动力学测量的算法以及解析延拓方案。此外，我们已经将我们的方法应用于不同的二维自旋系统。对于第二个资助期，我们现在计划集中我们的量子蒙特卡罗模拟来计算与散射探针相关的光谱函数，例如共振非弹性X射线散射（RIXS）或红外吸收光谱。我们计划特别是双自旋链和可变宽度的自旋梯系统，以及二维磁有序系统和符号问题的自旋液相模型。这些研究将使我们能够详细探索在这样的系统中出现的磁振子束缚态，并为基本量子磁模型系统的高级光谱探测提供无偏的参考数据。此外，我们的目标是扩展我们的细化光谱探针，也探索量子自旋系统的纠缠特性，基于量子多体纠缠哈密顿量的光谱特性的数值确定的最新进展，在那里我们可以研究量子临界点和非常规有序和量子无序系统。