Exploring connections between superconductivity, unconventional quantum order, and Fermi surface reconstruction

探索超导性、非常规量子级和费米表面重建之间的联系

• 批准号: RGPIN-2019-06446
• 负责人: Julian, Stephen
• 金额: $ 2.99万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715717
• 关键词: Exploring; connections; between; superconductivity; unconventional

We are in the midst of a materials revolution that is changing the face of technologies such as computation, solar energy, strong materials, and beyond. Superconductivity has an important future role to play, in power generation and transmission, quantum computing, transportation, and magnet technology. This future, however, depends on our ability to explore new materials systems, and to better understand unconventional superconductivity. A huge advance in the physics of superconductors resulted from the discovery of heavy fermion, high-Tc copper-oxide, and iron-pnictide superconductors, but these discoveries revealed that there are deep physics issues that we don't understand, regarding the surprisingly intertwined physics of superconductivity, low-temperature magnetic phase transitions and, especially, Fermi surface reconstruction. The exploration of these issues has produced new and unexpected physics. My own research group, in our recent studies in this field, has been led into a broad range of topics: topological semi-metallic states in pyrochlore iridates, 'non-metallic metal' behaviour in frustrated magnetic metals, exotic quantum magnetism associated with Fermi surface transitions, and combined nuclear-electronic order parameters with a new kind of quantum critical point in praseodymium-based superconductors. At the same time we have added new experimental capabilities, so that we now have pressure cells that can reach 400 kilobar, and temperatures down to 10 mK, in magnetic fields up to 18 tesla. We use these to create novel states in complex matter. Now we want to add new capabilities: the ability to apply very large uniaxial stress within a high-pressure volume; to use electronic structure calculations to guide our pressure or uniaxial stress measurements; and to use modern focussed-ion-beam sample preparation to rapidly and reliably prepare high-pressure measurements. Such developments offer an excellent training ground for research students, and they will also allow us to advance rapidly. During this grant we will apply our capabilities to a variety of promising materials, as we also continue to work to understand recent discoveries in our group. An example of the former is Sr2RhO4, which is a cousin to high-temperature and topological superconductors. It has a distorted perovskite structure, and we will use electronic-structure calculations to understand how best to apply pressure to drive a very flat band, near the Fermi energy, across the Fermi energy, causing a major Fermi surface reconstruction and, I predict, superconductivity, perhaps even high temperature superconductivity. An example of an ongoing project is a new collaboration with a group in the UK to explore combined nuclear-electronic order to below 1 millikelvin. Our ultimate goal is new and improved superconducting technologies, but along the way there is a lot of new physics to explore.

我们正处于一场材料革命之中，这场革命正在改变计算、太阳能、高强度材料等技术的面貌。 超导未来在发电和传输、量子计算、交通和磁体技术方面将发挥重要作用。然而，这个未来取决于我们探索新材料系统以及更好地理解非常规超导性的能力。 重费米子、高 Tc 氧化铜和铁磷化物超导体的发现带来了超导体物理学的巨大进步，但这些发现揭示了存在着我们不理解的深层物理问题，即令人惊讶地交织在一起的物理问题。超导物理学、低温磁相变，特别是费米表面重建。对这些问题的探索产生了新的、意想不到的物理学。我自己的研究小组最近在这一领域的研究中，已经进入了广泛的主题：烧绿石铱酸盐中的拓扑半金属态、受挫磁性金属中的“非金属金属”行为、与费米相关的奇异量子磁性表面跃迁，并将核电子序参数与镨基超导体中的新型量子临界点相结合。 同时，我们还增加了新的实验能力，因此我们现在拥有可以达到 400 kilobar 的压力单元，温度低至 10 mK，磁场高达 18 特斯拉。我们用它们在复杂物质中创造新的状态。 现在我们要添加新功能：在高压体积内施加非常大的单轴应力的能力；使用电子结构计算来指导我们的压力或单轴应力测量；并使用现代聚焦离子束样品制备来快速可靠地准备高压测量。 这些发展为研究生提供了良好的训练场地，也使我们能够快速进步。 在这笔资助期间，我们将把我们的能力应用于各种有前途的材料，同时我们还将继续努力了解我们小组的最新发现。前者的一个例子是 Sr2RhO4，它是高温拓扑超导体的近亲。它具有扭曲的钙钛矿结构，我们将使用电子结构计算来了解如何最好地施加压力来驱动费米能量附近的非常平坦的带，穿过费米能量，从而导致主要的费米表面重建，并且我预测，超导，甚至可能是高温超导。 正在进行的项目的一个例子是与英国一个小组的一项新合作，旨在探索低于 1 毫开尔文的核电子组合顺序。 我们的最终目标是新的和改进的超导技术，但在此过程中还有很多新的物理学需要探索。