Manipulating the strong quantum spin fluctuations in triple perovskites with effective spin-1/2 triangular lattice

摘要：虽然量子计算机的兴起可能有一天有助于解决复杂问题并以不可破解的安全性传递信息，但缺乏可扩展实现量子技术的物质平台。例如，著名的量子自旋液体（QSLs）最有趣的磁性是量子力学加密和信息传输的可能性，不受环境影响。尽管对qsl进行了广泛的研究，但它们离应用还很遥远。第一个障碍是缺乏对物质新阶段的理解。人们普遍认为，强量子自旋涨落（QSFs）在QSL中起着至关重要的作用，但QSFs究竟如何导致QSL态或其他奇异的量子磁现象尚不清楚。第二个障碍是，大多数研究的量子激光器都是绝缘体和电子惰性的，这与依赖于移动载流子的电路不兼容。最大的挑战是找到一种方法，通过“金属化”量子磁体，将纠缠信息转换成移动充电信号。该项目将采用独特的方法，使用战略材料设计来解决这两个障碍。该项目还将支持两名研究生的教育和活动。首席研究员的教育工作是吸引本科生和高中生进入科学和技术的现实世界，并通过弥合研究和教育环境之间的差距，激励他们追求科学事业。主要活动包括：(i)通过将PI的研究项目和研究设施整合到现有的本科课程中，将实验室带入课堂；（ii）通过举办暑期研讨会，将课堂带入实验室；（三）通过田纳西州州长暑期学校接触高中生。技术摘要：本项目将重点研究三钙钛矿A3BC2O9，其中有效自旋为1/2的磁性离子形成二维等边三角形晶格。因此，该系统符合最大化qsf的所有要求。在A位或C位上的化学取代很容易给体系带来扰动，如各向异性和猝灭无序。此外，PI还可以利用其“三明治”结构，通过结合高压，探索量子磁体的金属化。该方法包括：(1)新的三重钙钛矿的晶体生长；（ii）通过低温、高磁场和高压的互补测量，包括交流磁化率、比热、导热系数、电阻率、弹性和非弹性中子散射以及对分布函数的总散射等，研究了qsf对扰动的反应以及夹层结构在高压下的物理性质（PDF）。预期结果将提供(i)新的QSL候选者和新的QSL搜索指南；（ii）金属化量子磁体的新方向和关于流动电子如何与量子自旋态相互作用的基本知识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Abstract:While the rise of quantum computers may one day help solve complex problems and deliver information with unhackable security, there is lack of a material platforms for scalable realization of quantum technologies. For instance, the most interesting magnetic property of the celebrated quantum spin liquids (QSLs) is the possibility of quantum mechanical encryption and transport of information, protected against environmental influences. Despite extensive studies on QSLs, they are still far away from applications. First obstacle is the shortage of understanding of this new phase of matter. The common belief is that the strong quantum spin fluctuations (QSFs) play a critical role in QSLs but how exactly QSFs lead to QSL state or other exotic quantum magnetic phenomena is not clear. Second obstacle is that most of the studied QSLs are insulators and electronically inert, which is incompatible with an electrical circuit that relies on moving charge carriers. The grand challenge is to find a way to convert the entanglement information into mobile charge signal by “metallizing” quantum magnets. This project will take a unique approach by using strategical materials design to address these two obstacles. The project also will support the education and activities of two graduate students. The principal investigator’s educational effort is to attract undergraduate and high school students to the real world of science and technology and to motivate them to pursue careers in science by bridging the gap between research and educational settings. The main activities include: (i) bringing the lab to the classroom by integrating the exposure to the PI’s research program and research facility into existing undergraduate courses; (ii) bringing the classroom to the lab by developing a summer seminar; (iii) reach out to high school students through the Governor Summer School of the Tennessee state.Technical Abstract:This project will focus on triple perovskites A3BC2O9, in which the effective spin-1/2 magnetic ions form a two-dimensional equilateral triangular lattice. Therefore, this system fits all the requirements for maximized QSFs. The chemical substitution on A sites or C sites can easily introduce perturbations, such as anisotropy and quenched disorder into the system. Moreover, the PI also can use its “sandwich” structure, by combining high pressure, to explore the metallization of quantum magnets. The approach includes (i) crystal growth of the new triple perovskites; (ii) studies on how the QSFs react to the perturbations and how the physical properties of the sandwich structure involve under high pressure by complementary low temperature, high magnetic field, and high pressure measurements, including AC susceptibility, specific heat, thermal conductivity, resistivity, elastic and inelastic neutron scattering, and total scattering for pair distribution function (PDF). The expected outcomes will provide (i) new QSL candidates and guidelines for new QSL search; (ii) a new direction for metallizing quantum magnets and fundamental knowledge about how the itinerant electrons interact with quantum spin states.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.