EAGER: Exploring the Role of Copper Sulfides in Room Temperature Superconductors

EAGER：探索硫化铜在室温超导体中的作用

• 批准号: 2403985
• 负责人: Efrain Rodriguez
• 金额: $ 30万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-12-01 至 2025-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2403985&HistoricalAwards=false
• 关键词: EAGER; Exploring; Role; Copper; Sulfides

Non-technical SummaryMaterials make technological progress possible. For example, the battery materials inside laptops and smartphones enable the portability of these electronic devices by charging and recharging them. The magnetic materials in windmills allow them to harness the wind to generate the electricity that powers homes and businesses. It has long been a dream of scientists who study materials to discover one that would enable many technologies at once. Such a miracle material exists in the superconductor. It would enable applications in energy, human health, and computing technologies. In the last century, many such superconductors have been found, but they all have one major setback. These materials become superconductors only at extremely low temperatures. These temperatures are even lower than the coldest recorded temperature on Earth. Furthermore, the handful of materials that are superconducting near room temperature require pressures found only near the center of the planet. Therefore, the long-sought goal of scientists has been to find a material that is an effective superconductor near room temperature and at pressures on the surface of the Earth. This EAGER award, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, will examine the role the byproducts consisting of copper and sulfur play in a sample reported to be such a miracle material in 2023. This endeavor includes the careful preparation of samples consisting of copper and sulfur and testing them under the most rigorous conditions to uncover the world’s first potential room-temperature superconductor. Technical SummaryThis EAGER award, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, will explore the role that copper sulfides plays in the potential room-temperature superconductor called LK-99 reported in 2023. The research team at the University of Maryland carries out solid state chemistry studies to isolate the copper sulfide minority phase contained in LK-99. Unlike in the LK-99 manuscripts, however, the working hypothesis here is that it is more likely that this minority phase, Cu2-xS, is the superconductor and not the majority phase, lead oxyapatite, which is a known wide-band gap insulator. This hypothesis was formed since Cu2S displays interesting high-temperature physics including a superionic phase transition, a crystallographic phase transition, and an insulator-to-metal transition. The latter is an electronic one driven by the hole-doping brought on by copper site vacancies, which is the x in Cu2-xS. Since these transitions also occur near 380 K, they would explain why the room-temperature superconductivity reported in LK-99 should be attributed to Cu2-xS. The approach here is to charge dope this phase by forming Cu2-xMxS phases where M is a metal with a different valence state from Cu+. This strategy is similar to suppressing phase transitions in the cuprates and iron-based superconductors, whereby electron or hole doping suppresses an antiferromagnetic phase transition, and a superconducting regime appears on the phase diagram. In the case of Cu2S, the relevant driver is not magnetism as in the cuprates and iron pnictides, but rather ionic forces coupled to the electronic structure that could drive the unconventional behavior. This EAGER grant surveys phase pure samples of different forms of Cu2-xS and Cu2-xMxS to understand how their crystallographic, heat and electronic transport, and magnetic properties change as a function of x. The research activities use both polycrystalline and single crystal samples to establish whether this phase is indeed the key to understanding the room-temperature Meissner effect reported in LK-99.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.

非技术摘要材料使技术进步成为可能，例如，笔记本电脑和智能手机中的电池材料可以通过充电和充电来实现这些电子设备的便携性，风车中的磁性材料使它们能够利用风来发电，为家庭提供电力。长期以来，研究材料的科学家们一直梦想着发现一种能够同时实现多种技术的材料，它将能够在能源、人类健康和计算技术中得到应用。最后的近一个世纪以来，已经发现了许多这样的超导体，但它们都有一个重大缺陷，即这些材料只能在极低的温度下才能成为超导体，而且这些温度甚至低于地球上有记录的最冷温度。室温需要仅在地球中心附近存在的压力，因此，科学家们长期以来的目标是找到一种在室温附近和地球表面压力下有效的超导体材料。该奖项由 NSF 材料研究部的固态和材料化学项目支持，将研究由铜和硫组成的副产品在 2023 年据称是一种神奇材料的样品中所发挥的作用。这项工作包括精心准备由铜和硫组成的样品，并在最严格的条件下对其进行测试，以发现世界上第一个潜在的室温超导体。 NSF 材料研究部的化学项目将探索硫化铜在 2023 年报道的名为 LK-99 的潜在室温超导体中所发挥的作用。马里兰大学的研究团队进行固态化学研究，以分离铜然而，与 LK-99 手稿中包含的硫化物少数相不同，这里的工作假设更可能是这种少数相 Cu2-xS，是超导体，而不是主要相，即铅氧磷灰石，它是一种已知的宽带隙绝缘体，因为 Cu2S 显示出有趣的高温物理特性，包括超离子相变、晶体相变和绝缘体相变。后者是由铜位点空位引起的空穴掺杂驱动的电子跃迁，即 Cu2-xS 中的 x，因为这些跃迁也发生在 380 附近。 K，他们将解释为什么 LK-99 中报告的室温超导性应归因于 Cu2-xS。这里的方法是通过形成 Cu2-xMxS 相来对该相进行电荷掺杂，其中 M 是价态不同的金属。 Cu+ 这种策略类似于抑制铜酸盐和铁基超导体中的相变，通过电子或空穴掺杂抑制反铁磁相变，从而出现超导状态。在相图上，相关的驱动因素不是铜酸盐和铁磷化物中的磁性，而是与电子结构耦合的离子力，该力可以驱动不同的相纯样品。 Cu2-xS 和 Cu2-xMxS 的形式，以了解它们的晶体学、热和电子传输以及磁性如何随着 x 的变化而变化。确定这一阶段是否确实是理解 LK-99 中报告的室温迈斯纳效应的关键。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。