Discovery of Compounds containing Frustrated Vanadium Nets with Emergent Electronic Phenomena

非技术摘要：新的复杂量子材料的出现对量子信息、传感和计算的持续发展至关重要。最近发现了带有受挫的钒亚晶格的三元化合物，这意味着磁自旋不能在交替的方向上排列(想象一下把自旋放在三角形的角落上)，揭示了驻留在单一材料中的多种奇异现象，包括超导电性。更耐人寻味的是，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具有挑战性，因为只有几个具体的例子是已知的。在NSF材料研究部固态和材料化学计划的支持下，Toberer教授和他的研究小组采用了各种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)已知化合物和假想化合物的第一性原理计算和(Ii)整体合成和结构确定相结合的方法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，单晶是由最有希望用于进一步低温测量的化合物生长的。总而言之，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本科生的教育机会和与更广泛的公众的科学接触。其中包括夏季研究机会，关于固态化学与矿物学和宝石学交叉的公开讲座，以及为来自科罗拉多州农村地区的学生举办的为期一周的固态化学夏令营。技术摘要在NSF材料研究部固态和材料化学计划的支持下，Toberer教授和他的研究小组试图发现新类型的钒极性金属间化合物，其中电子关联和拓扑能带结构在磁性受挫的晶格上相交。这项研究的灵感来自于最近在KV3Sb5和REV6Sn6材料类中的发现；这些化合物含有钒Kagome亚晶格，可以产生重要的拓扑结构、电荷密度波和超导电性。这项研究首先使用块状固态化学方法实验建立了三元A-V-Z相图和相关的新型化合物；这些努力利用了第一性原理计算和物理信息的贝叶斯优化的指导。对于每个新化合物，使用第一原理方法预测每个新化合物的电子结构和拓扑结构，以使用助熔剂进行单晶生长的向下选择。对这些单晶的低温表征揭示了磁性受挫引起的潜在电子不稳定性；通过承诺与更广泛的凝聚态社区共享样品，进一步的表征是便利的。基于受挫钒网的新型量子材料的发现和研究将最终加深我们对拓扑、电荷密度波和超导电性之间相互作用的理解。这些活动交织在一起的是努力(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)通过有针对性的拓展扩大对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NSF的法定使命，并通过使用基金会的智力优势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.