Superexchange, effective interactions, and magnetic ground states in frustrated triangular-lattice quantum magnets

受挫三角晶格量子磁体中的超级交换、有效相互作用和磁性基态

• 批准号: 441216021
• 负责人: Dr. Liviu Hozoi
• 金额: --
• 依托单位: Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden (IFW) e.V.
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/441216021?language=en
• 关键词: Superexchange; effective; interactions; magnetic; ground

In the context of strongly-correlated electronic systems, quantum spin liquids (QSL's) represent an area of active investigation ever since the basic concept was proposed in 1973. The various types of less conventional excitations that may arise in QSL's generated particular interest not only in fundamental scientific research but also at the level of possible device applications. For example, materials supporting QSL states were indicated as potential platforms for topological quantum computation. Finding systems in which QSL ground states are realized necessitated a few decades of materials exploration. The results of these efforts were for a while disappointing but more recently several types of crystalline compounds carrying the signatures of QSL physics have been reported. In this frame of reference, we would like to throw light on the underlying magnetic interactions in triangular-lattice compounds of major present interest, d-electron- and also f-electron-based, using advanced quantum-chemical electronic-structure computations.In the first category, we target the triangular-lattice system KxIr(1-x/4)O2 but also Na2Pt0.5Ir0.5O3 and K0.5RuCl3. The main motivation here is provided by recent measurements suggesting a QSL ground state in K0.85Ir0.79O2. The most interesting aspect to be clarified with this project is the ratio between the Kitaev and Heisenberg interactions K/J (ratios larger than 6, defining the so-called Kitaev regime, are found in some honeycomb iridates and in RuCl3) but also the strength of the offdiagonal effective exchange parameters (so-called Γ's). Such information is essential for understanding the nature of the magnetic ground state in triangular-lattice KxIr(1-x/4)O2.In relation to f-electron quantum magnetism, no detailed quantum-chemical investigations are available to our knowledge on 4f-4f superexchange in solids. With this research project we would like to change this present state of affairs. What acted here as a catalyst is the current excitement around 4f triangular-lattice materials, strong candidates to the realization of QSL's. There are reasons to believe that the largest intersite magnetic couplings arise in triangular-lattice KCeS2. For first insights into 4f-4f superexchange and for calibration purposes, we will therefore focus in a first step on KCeS2. Possible extensions are then NaYbSe2, NaYbS2, and NaYbO2.

在强相关电子系统的背景下，自 1973 年提出基本概念以来，量子自旋液体 (QSL) 代表了一个积极研究的领域。QSL 中可能出现的各种类型的非传统激发引起了特别的兴趣，而不是不仅在基础科学研究方面，而且在可能的设备应用层面上，例如，支持 QSL 态的材料被认为是拓扑量子计算的潜在平台，需要几十年的材料。这些努力的结果一度令人失望，但最近报道了几种带有 QSL 物理特征的晶体化合物，在这个参考框架中，我们希望阐明三角磁相互作用的基础。目前主要关注的晶格化合物，基于 d 电子和 f 电子，使用先进的量子化学电子结构计算。在第一类中，我们的目标是三角晶格系统KxIr(1-x/4)O2 以及 Na2Pt0.5Ir0.5O3 和 K0.5RuCl3 是由最近的测量提供的，表明 K0.85Ir0.79O2 中存在 QSL 基态 这是需要澄清的最有趣的方面。该项目是基塔耶夫和海森堡相互作用 K/J 之间的比率（大于 6 的比率，定义所谓的基塔耶夫政权，可在一些蜂窝状铱酸盐和 RuCl3），以及非对角有效交换参数（所谓的 Γ）的强度，这些信息对于理解三角晶格 KxIr(1-x/4)O2 中磁性基态的性质至关重要。关于 f 电子量子磁性，根据我们对固体中 4f-4f 超交换的了解，还没有详细的量子化学研究，我们希望通过这个研究项目来改变这一点。目前的情况起到了催化剂的作用，目前对 4f 三角晶格材料的兴奋是实现 QSL 的有力候选者，有理由相信最大的位点间磁耦合首先出现在三角晶格 KCeS2 中。为了深入了解 4f-4f 超级交换并出于校准目的，我们将首先关注 KCeS2，然后可能的扩展是 NaYbSe2， NaYbS2 和 NaYbO2。