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具有受挫的钒亚晶格，这意味着磁自旋不能以交替方向排列（想想把自旋放在三角形的角上），揭示了多种奇异现象，包括超导性，存在于单一材料中。更有趣的是，这些现象被发现相互作用和竞争。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。通过这个项目，由NSF材料研究部的固态和材料化学计划支持，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原理计算和（ii）本体合成和结构测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的钒三元化合物的基本性质。第三，单晶生长的最有前途的化合物进一步低温测量。总之，这些任务有望实现下一代量子材料。这些努力交织在一起的是本科生的教育机会和与更广泛公众的科学接触。 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，以及为期一周的固态化学夏令营，供来自科罗拉多农村地区的学生参加。技术摘要在NSF材料研究部门的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的钒极性金属间化合物，其中电子相关性和拓扑能带结构在磁阻格上相交。这项研究的灵感来自于最近在KV 3Sb 5和REV 6Sn 6材料类别中的发现;这些化合物含有钒kagome亚晶格，这些亚晶格产生了非平凡的拓扑结构，电荷密度波和超导性。研究开始于使用散装固态化学方法实验建立三元A-V-Z相图和相关的新化合物;这些努力利用了第一原理计算和物理学贝叶斯优化的指导。对于每种新化合物，使用第一原理方法预测每种新化合物的电子结构和拓扑结构，用于使用助熔剂的单晶生长的向下选择。这些单晶的低温表征揭示了磁挫折产生的潜在电子不稳定性;通过与更广泛的凝聚态物质社区共享样品的承诺，促进了进一步的表征。基于受抑钒网的新量子材料的发现和研究将最终增强我们对拓扑结构、电荷密度波和超导性之间相互作用的理解。这些活动交织在一起，努力（i）在固态材料化学，凝聚态物理学和统计决策的交叉点上培养新一代STEM人才，（ii）通过有针对性的推广扩大对STEM的参与，及（iii）让更广泛的公众参与-该奖项反映了NSF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进行评估，被认为值得支持的搜索.

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.