Quantum Phases in spin-orbit coupled honeycomb magnets: beyond 4d and 5d transition metal ions

非技术摘要：物质的量子相是基于限制在晶格中的电子之间的纠缠。一个熟悉的例子是超导性;这种曾经的奇异现象现在已经成熟，并被用于磁共振成像（MRI）等技术应用。 同样，在这项关于蜂窝晶格磁体的研究中探索的物质的新量子相（即，由六边形组成的晶格结构构建的磁体）可以提供戏剧性的技术后果。 一个预测的量子相，Kitaev蜂巢量子自旋液体，支持特殊的激发态，可以形成量子计算的异常强大的“量子位”。 该研究项目旨在使用以前未探索的磁性离子选择在新的蜂窝晶格材料中产生这种奇异相。 本科研究人员准备样品并执行磁性表征的基本技术，进行了大部分研究的探索性方面。 参与此计画的研究生掌握单晶成长、热力学特性及非弹性中子散射的技术。 该项目在很大程度上依赖于美国的大型中子科学设施。技术摘要：这项研究旨在使用非常规材料选择产生新的量子相物质。 具有强自旋轨道耦合的磁性绝缘体是探索各种基于量子纠缠的有趣相的理想目标，例如量子自旋液体。 这些奇异的相位主机潜在有用的准粒子激发;一个例子是“任意子”激发预测的Kitaev蜂窝量子自旋液体。 任意子一旦在真实的材料中成功产生，就可以用于拓扑保护的量子计算。 像这样的奇异相的两个关键成分是1）蜂窝晶格上的各向异性磁相互作用，可从具有强自旋轨道耦合的磁性物质获得，以及2）量子涨落，这是相关伪自旋1/2磁矩的自然特征。 这些成分先前已经在基于4d和5d过渡金属离子的蜂窝晶格材料中寻找。 目前的研究项目将搜索扩展到这些系列之外的磁性物种的非常规选择，从而实现更广泛的表征技术，同时开辟了一个新的材料竞技场。 固态合成方法，包括激烈的晶体生长的努力，结合使用热力学探针和非弹性中子散射在低至50 mK的温度下的材料的详细表征。 本科研究人员准备样品并执行磁性表征的基本技术，进行了大部分研究的探索性方面。 参与此计画的研究生掌握单晶成长、热力学特性及非弹性中子散射的技术。 该项目在很大程度上依赖于美国的大型中子科学设施。

Non-Technical Abstract:Quantum phases of matter are based on entanglement between electrons confined to crystal lattices. A familiar example of such a phase is superconductivity; this once-exotic phenomenon has now matured and is being used for technological applications such as Magnetic Resonance Imaging (MRI). Similarly, the new quantum phases of matter being explored in this research on honeycomb lattice magnets (i.e., magnets built from a lattice structure composed of hexagons) could provide dramatic technological consequences. One predicted quantum phase, the Kitaev Honeycomb Quantum Spin Liquid, supports special excited states that could form unusually robust "qubits" for quantum computations. This research project aims to produce such exotic phases in new honeycomb lattice materials, using previously unexplored choices of magnetic ions. Undergraduate researchers, who prepare samples and perform basic techniques for magnetic characterizations, carry out a large part of the exploratory aspects of the research. Graduate students involved in this project master techniques in single crystal growth, thermodynamic characterization, and inelastic neutron scattering. This project heavily relies on large-scale neutron science facilities in the United States.Technical Abstract:This research is designed to produce new quantum phases of matter using unconventional materials choices. Magnetic insulators with strong spin-orbit coupling are ideal targets for exploring a wide variety of interesting phases based on quantum entanglement, such as Quantum Spin Liquids. These exotic phases host potentially useful quasi-particle excitations; one example is the "anyon" excitation predicted for the Kitaev Honeycomb Quantum Spin Liquid. Anyons, once they are successfully produced in a real material, could be used for topologically protected quantum computations. The two key ingredients for exotic phases like this are 1) anisotropic magnetic interactions on the honeycomb lattice, obtainable from magnetic species with strong spin-orbit coupling, and 2) quantum fluctuations, which are a natural feature of correlated pseudo-spin ½ magnetic moments. These ingredients have previously been sought in honeycomb lattice materials based on 4d and 5d transition metal ions. The current research project extends the search to unconventional choices of magnetic species outside of these series, enabling a wider variety of characterization techniques while opening a new arena of materials to be explored. Solid-state synthesis methods, including intense crystal growth efforts, are combined with detailed characterizations of materials using thermodynamic probes and inelastic neutron scattering at temperatures as low as 50 mK. Undergraduate researchers, who prepare samples and perform basic techniques for magnetic characterizations, carry out a large part of the exploratory aspects of the research. Graduate students involved in this project master techniques in single crystal growth, thermodynamic characterization, and inelastic neutron scattering. This project heavily relies on large-scale neutron science facilities in the US.