Discovery of Compounds containing Frustrated Vanadium Nets with Emergent Electronic Phenomena

非技术摘要：新型复杂量子材料的出现对于量子信息、传感和计算的持续发展至关重要。最近发现的三元化合物的钒亚晶格受挫，这意味着磁自旋不能在交替方向上排列（想想把自旋放在三角形的四个角上），揭示了存在于单一材料中的多种奇异现象，包括超导性。更有趣的是，这些现象被发现是相互作用和竞争的。理解这些相互作用的含义是具有挑战性的，因为只有少数材料的例子是已知的。在这个由NSF材料研究部固态和材料化学项目支持的项目中，Toberer教授和他的研究小组采用策略来发现含有磁性钒原子层的新晶体化合物。首先，利用主动搜索算法通过(i)已知和假设化合物的第一性原理计算和（ii）体合成和结构确定的组合来有效地探索三元钒化学空间。其次，通过低温测量和量子力学计算确定了新型钒三元化合物的基本性质。第三，单晶是最有希望用于进一步低温测量的化合物。总之，这些任务有望使下一代量子材料成为可能。这些努力交织在一起的是为本科生提供教育机会和与更广泛的公众进行科学接触。其中包括夏季研究机会，固态化学与矿物学和宝石学交叉的公开讲座，以及为科罗拉多州农村地区的学生提供为期一周的固态化学夏令营。技术摘要：在美国国家科学基金会材料研究部固态和材料化学项目的支持下，Toberer教授和他的研究小组试图发现新型的钒极性金属间化合物，其中电子相关性和拓扑带结构在磁受挫晶格上相交。这项研究的灵感来自于最近在KV3Sb5和REV6Sn6材料类别中的发现；这些化合物含有钒kagome亚晶格，产生非平凡的拓扑结构、电荷密度波和超导性。研究开始于实验建立三元A-V-Z相图和相关的新化合物，其中使用大块固体化学方法；这些努力利用第一性原理计算和物理知识贝叶斯优化的指导。对于每个新化合物，每个新化合物的电子结构和拓扑结构都是用第一性原理方法预测的，用于单晶生长的下选择。这些单晶的低温表征揭示了磁挫折引起的潜在电子不稳定性；进一步的表征是通过与更广泛的凝聚态物质社区的样品共享的承诺。基于受挫钒网的新量子材料的发现和研究将最终增强我们对拓扑、电荷密度波和超导性之间相互作用的理解。贯穿这些活动的努力是(i)在固态材料化学、凝聚态物理和统计决策的交叉领域培养新一代STEM人才，（ii）通过有针对性的外展扩大STEM的参与，以及（iii）让更广泛的公众参与固态化学。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:The emergence of new, complex quantum materials is critical for continued developments in quantum information, sensing, and computing. Recent discoveries of ternary compounds with frustrated vanadium sublattices, meaning magnetic spins cannot arrange in alternating directions (think putting the spins on the corners of a triangle), have revealed multiple exotic phenomena, including superconductivity, residing within a single material. Even more intriguingly, these phenomena are found to interact and compete. Understanding the implications of these interactions is challenging because only a few material examples are known. With this project, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, Prof. Toberer and his research group employ strategies to discover new crystalline compounds that contain layers of magnetic vanadium atoms. First, active search algorithms are utilized to efficiently explore ternary vanadium chemical spaces through a combination of (i) first principles calculations of known and hypothetical compounds and (ii) bulk synthesis and structure determination. Second, the fundamental properties of new vanadium ternary compounds are determined through low temperature measurements and quantum mechanical calculations. Third, single crystals are grown of the most promising compounds for further low temperature measurements. Together, these tasks are expected to enable the next generation of quantum materials. Interwoven throughout these efforts are educational opportunities for undergraduate students and scientific engagement with the broader public. These include summer research opportunities, public lectures on the intersection of solid-state chemistry with mineralogy and gemology, and a week-long summer camp on solid-state chemistry for students from rural areas of Colorado. Technical abstractWith support from the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, Prof. Toberer and his research group seek to uncover new classes of vanadium polar intermetallics compounds where electronic correlations and topological band structures intersect on magnetically frustrated lattices. The inspiration for this research comes from recent discoveries within the KV3Sb5 and REV6Sn6 material classes; these compounds contain vanadium kagome sublattices that give rise to nontrivial topology, charge density waves, and superconductivity. The research begins with experimentally establishing ternary A-V-Z phase diagrams and associated novel compounds therein using bulk solid state chemistry approaches; these efforts leverage guidance from first principles calculations and physics-informed Bayesian optimization. For each new compound, the electronic structure and topology of each new compound is predicted using first principles methods for down-selection for single crystal growth using fluxes. Low temperature characterization of these single crystals reveals potential electronic instabilities arising from magnetic frustration; further characterization is facilitated through a commitment to sample sharing with the broader condensed matter community. The discovery and study of new quantum materials based on frustrated vanadium nets will ultimately enhance our understanding of the interaction between topology, charge density waves, and superconductivity. Interwoven throughout these activities are efforts to (i) build a new generation of STEM talent at the intersection of solid-state materials chemistry, condensed matter physics, and statistical decision making, (ii) broaden participation in STEM via targeted outreach, and (iii) engage the broader public in solid-state chemistry.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.