Controlling Exchange and Quenched Disorder in Low-Dimensional Spin Systems

研究新材料的结构和物理特性是开发创新产品和技术的基础，因此对社会非常重要，因为这些知识产生了附加价值。我们快速发展的经济需要对新材料的物理特性进行更系统的分析，以便在其成分发生变化时对其有一个充分的了解。这可以通过专门利用这些新发现开发新产品来增强技术优势。因此，研究不应仅仅强调新材料的开发，而应了解如何开发具有预定义特性的特定材料。通过对组成和关系的综合和表征，阐明了决定相关总体系集体行为的排序机制，从而深入了解了物理性质改变的方案。此外，由于可以通过非热控制参数对量子临界点周围的相进行建模，淬火失序可以导致具有有趣新性质的奇异临界点。本研究项目“控制低维自旋系统中的交换和淬火无序”主要研究中子散射的相关关系。本文研究了以下三种低维自旋系统，这些系统是由歌德大学的研究员设计和培养的，非常适合于本研究项目：a)在模型各向异性三角形晶格材料Cs2CuCl4-xBrx上，我们研究了准一维受挫系统中淬火无序的影响；b)在新的金属有机化合物K(C8H16O4)2CuCl3 H2O上，我们将研究相互作用的量子二聚体单元中的自旋相关性；c)在Ba1-xSrxCuSi2O6上，我们将探索二维量子临界点下玻色-爱因斯坦凝聚的令人兴奋的物理现象。

Investigation of structural and physical properties of new materials is the basis for the development of innovative products and technologies and therefore of high importance for the society as this knowledge produces an added value. Our rapidly evolving economy requires an even more systematic analysis of the physical properties of new materials to gain a sound understanding thereof in case of a modification of their composition. This allows enhancing technological ascendancy by specifically using such new findings for the development of new products. Therefore, research should not emphasis merely on the development of new materials, but on the understanding how to develop specific materials with pre-defined characteristics. Insights into the scheme of modification of physical properties are gained through synthesis and characterization of compositions and relations, elucidating the ordering mechanism, which determines the collective behavior of i.e. a correlated total system. Furthermore, as modeling of phases around quantum critical points are realizable through nonthermal control parameter, quenched disorder can lead to exotic critical points with interesting new properties. This research project Controlling Exchange and Quenched Disorder in Low-Dimensional Spin Systems focuses on the investigation of correlations by neutron scattering. It deals with the following three low-dimensional spin systems, designed and grown by the fellow at Goethe-University and which are very well suited for this research project: a) on the model-anisotropic triangular lattice material Cs2CuCl4-xBrx we study the effects of quenched disorder in quasi-one-dimensional frustrated systems; b) on the new metal-organic compound K(C8H16O4)2CuCl3 H2O we will investigate spin-correlations in interacting quantum dimer units, and c) in Ba1-xSrxCuSi2O6 we will explore the exciting physics of Bose-Einstein condensation at a two-dimensional quantum critical point.