High-Pressure Synthesis of Missing Pnictide Superconductors

第1部分：非技术摘要：电能无损传输是指进入材料的所有电能都能无损地传输。如果实现，这将带来惊人的能源节约，彻底改变能源产生方式，并显著改善医疗成像技术。所谓的超导体证明了这种无损的电力传输，这使得它们对新技术非常重要。超导体也为基础科学发现提供了潜力。超导体实现这种节能现象的机制在很大程度上还没有得到很好的理解。了解这一机制并创造更好的超导体对于技术应用至关重要，因为目前超导在很大程度上是一种低温现象，超导体的临界温度与火星上甚至外太空最冷地区的极低温相似。通过该奖项，由固态和材料化学以及NSF材料研究部的凝聚态物理项目资助，弗里德曼的研究团队从事理论启发的研究，寻找特定类型的新型超导体，这可以使人们对超导机制有基本的了解。她的团队使用高压合成来获得化学家长期以来无法获得的新化合物。这项工作为研究生和博士后提供了跨学科的培训，使他们受益于固体化学、物理学和地球物理学的科学交叉。让研究生做好跨领域合作的准备，加强了我们下一代从事科学工作的劳动力。第2部分：技术总结：高温超导的实现将是一个变革性的进步，从改善医学成像到容错电力传输，这对NSF各部门都有影响。到目前为止，绝大多数新的超导体要么是偶然发现的，要么是对已知超导系统的修改，要么是通过对理论上不太可能的候选者的研究发现的。与之形成鲜明对比的是，由于预测新型超导材料的固有困难，新体系的定向合成尚不发达。为了实现合理的进展，需要一个明确的设计策略，这就需要知道在给定类别的超导体中运行的超导机制。Freedman提出了通过高压合成明显缺失的Fe-Bi镍基超导体亚类。这项工作的动机是Freedman最近在固态中发现的第一个Fe-Bi键，通过高压的应用实现，并通过形成Bi-Bi相互作用来稳定。该奖项由美国国家科学基金会材料研究部固态和材料化学以及凝聚态物理项目资助，Freedman的团队通过原位和体x射线衍射和光谱方法表征了新材料。材料通过磁强计、电阻率和热容测量进行物理探测。这些数据的汇总提供了对超导机制的深入了解，以及可能的结构-功能相关性。创造和理解不同的超导体为这一复杂领域的真正发现提供了希望。一种新型超导体的实现将促进跨科学的合作，并使人们对超导有更深入的了解。超导体还具有巨大的社会影响潜力，从核磁共振成像仪器到通过电网增加电力传输。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。

Part 1: Non-Technical summary: Lossless transmission of power means that all electricity that goes into a material is transported without loss. If achieved, this would lead to astonishing energy savings, completely transform energy generation, and significantly improve medical imaging technology. So-called superconductors demonstrate this lossless transmission of electricity making them very important for novel technologies. Superconductors also offer the potential for fundamental scientific discovery. The mechanism by which superconductors enable this energy saving phenomenon is largely not well understood. Understanding this mechanism and creating better superconductors is essential for technological application, because currently superconductivity is largely a low-temperature phenomenon, with critical temperatures for superconductors being similar to the extremely low temperatures found on Mars or even in the coldest regions of outer space. Through this award, funded by the Solid State and Materials Chemistry as well as the Condensed Matter Physics programs in the Division of Materials Research at NSF, Freedman's research team engages in a theory-inspired search for new superconductors of a specific type, which could enable fundamental insight into the mechanism of superconductivity. Her team uses high-pressure synthesis to access new compounds that have long eluded chemists. This work enables interdisciplinary training for graduate students and postdoctoral fellows, where they benefit from the scientific intersection of solid-state chemistry, physics and geophysics. Preparing graduate students to collaborate across fields strengthens the next generation of our scientifically engaged workforce.Part 2: Technical summary: The realization of high temperature superconductivity would be a transformative advance, with implications across NSF directorates ranging from improved medical imaging to fault tolerant power transmission. Thus far, the vast majority of new superconductors have been found either by serendipity, modification of known superconducting systems, or through the investigation of theoretically unlikely candidates. In stark contrast, the targeted synthesis of new systems is underdeveloped, owing to the inherent difficulty of predicting new superconducting materials. To enable rational progress, a clear design strategy is needed, which necessitates knowing the operative superconducting mechanism in a given class of superconductors. Freedman proposes the synthesis of the notably missing subclass of Fe-Bi pnictide superconductors via high-pressure synthesis. This work is motivated by Freedman's recent discovery of the first Fe-Bi bond in the solid-state, achieved through the application of high pressure and stabilized by the formation of Bi-Bi interactions. Through this award, funded by the Solid State and Materials Chemistry as well as the Condensed Matter Physics programs in the Division of Materials Research at NSF, Freedman's team characterizes novel materials both through in situ and bulk X-ray diffraction and spectroscopic methods. Materials are physically probed via magnetometry, resistivity, and heat capacity measurements. The aggregate of these data provides insight into the mechanism of superconductivity, and possible structure-function correlations. Creating and understanding different superconductors offers promise for true discovery within this complex field. The realization of a new class of superconductors would foster collaborations across the sciences and enable a deeper understanding of superconductivity. Superconductors also have tremendous potential for societal impact, ranging from MRI instrumentation to increased power transmission through the electric grid.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.