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

基本信息

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：
2021
资助国家：
加拿大
起止时间：
2021-01-01 至 2022-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738915
关键词：
Exploring connections between superconductivity unconventional

项目摘要

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、强材料等技术的面貌，超导在未来的发电和传输、量子计算、运输等领域将发挥重要作用。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，超导体物理学的巨大进步源于重费米子、高温的发现。氧化铜和铁磷化物超导体，但这些发现揭示了我们不了解的深层物理问题，涉及超导性、低温磁相变以及特别是费米表面重建的令人惊讶的相互交织的物理问题。这些问题产生了新的、意想不到的物理学。在我们最近在这一领域的研究中，我们已经进入了广泛的主题：烧绿石中的拓扑半金属态。虹彩，受挫磁性金属中的“非金属金属”行为，与费米表面跃迁相关的奇异量子磁性，以及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。添加了新的实验功能，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，我们用这些来创造新颖的产品。现在我们想要添加新的功能：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；以及使用现代聚焦离子束。此类进展为研究生提供了良好的训练基础，并且在这笔资助期间，我们将把我们的能力应用到各种有前景的材料上。我们也继续前者的一个例子是 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实现这一点。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，导致主要的费米表面重建，并且我预测，超导性，甚至可能是高温超导性的一个例子。正在进行的项目之一是与英国的一个团队进行新的合作，探索低于 1 毫开尔文的组合核电子级数。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。