Using controlled disorder to probe quantum phase transitions under the dome of superconductivity

利用受控无序探测超导穹顶下的量子相变

• 批准号: 2219901
• 负责人: Ruslan Prozorov
• 金额: $ 57.92万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-12-01 至 2025-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219901&HistoricalAwards=false
• 关键词: Using; controlled; disorder; probe; quantum

Non-technical abstractModern technologies rely on the unusual properties of novel materials created in labs purposefully targeting needed functionalities. Of particular interest are materials exhibiting coexistence and interplay of seemingly incompatible properties, such as magnetic, electronic, and superconducting ordering of electrons. Sometimes one type of order dominates and quenches the other. The point where it happens at zero temperature is called a quantum critical point. The suppressed order does not give up easily, and the quantum critical regime in the vicinity of this point is full of surprising and largely unexplored properties. It is the goal of this project to identify these features and harness their unusual properties for future technologies, devices, and applications. Specifically, the team is studying complex materials where superconductivity coexists with charge-density wave. In this peculiar state, the electron density is spatially modulated while simultaneously superconducting. The interplay between these two ordering tendencies is tuned by the introduction of artificial scattering centers to study the underlying quantum critical point. The ultimate goal of this research is to learn how to harness the unusual physics of the quantum critical point. The research program provides an excellent hands-on training platform for a diverse group of undergraduate and graduate students in all aspects of experimental research. The underlying concepts and results of the project will be incorporated into an upper-level physics course to highlight the place of quantum criticality in modern condensed matter physics. Technical abstractThis proposal is systematically studying the interplay between charge-density-wave (CDW) and superconductivity (SC), not in a singular compound such as well-studied NbSe2, but in novel 3-4-13 stannides (Ca,Sr)3(Ir1-xRhx)4Sn13. In these compounds, the CDW is tuned continuously to a structural quantum critical point (QCP) by changing the composition. The results are compared with materials where spin-density-wave (SDW) coexists with superconductivity, specifically, (Ba,K)(Fe,T)2(As,P)2 (T=Co, Ni, Rh). QCPs under the dome of superconductivity in some of these systems have already been established. However, there is limited knowledge of their structure and response to disorder. Specifically, it is unknown how robust QCPs are to structural point-like disorder. Theoretical predictions range from the QCP completely disappearing, to being robust and even stabilized by disorder. The research involves structural, thermodynamic and transport measurements. In particular, x-ray scattering, muon spin rotation spectroscopy, electrical and thermal transport, London penetration depth, magnetization, and elastoresistivity. The measurements are performed across temperature-composition phase diagrams, emphasizing the quantum critical behavior near the QCP in the normal and the superconducting phases. Controlled point-like disorder introduced by MeV-range electron irradiation will perturb the studied systems at fixed chemical, electronic, and magnetic configurations. Specific questions being addressed are: (1) does SC weaken or protect the QCP? (2) is the QCP inside the SC state more robust against disorder than in the normal metal? (3) is the universality class of the QCP inside the SC phase the same as in the normal state? (4) are there novel emergent phenomena associated with disorder, such as large, rare regions leading to Griffiths singularities near the QCP?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.

非技术摘要现代技术依赖于在实验室中创造的新型材料的不寻常特性，目的是针对所需的功能。特别令人感兴趣的是材料表现出共存和相互作用的看似不相容的性质，如磁，电子和超导有序的电子。有时候，一种类型的秩序占主导地位，并熄灭另一种。在零温度下发生的点称为量子临界点。被抑制的秩序不会轻易放弃，在这一点附近的量子临界状态充满了令人惊讶的和基本上未被探索的性质。该项目的目标是识别这些功能，并利用其不寻常的属性为未来的技术，设备和应用程序。具体来说，该团队正在研究超导性与电荷密度波共存的复杂材料。在这种特殊的状态下，电子密度在空间上被调制，同时超导。这两种有序化趋势之间的相互作用是通过引入人工散射中心来研究潜在的量子临界点来调整的。这项研究的最终目标是学习如何利用量子临界点的不寻常物理学。该研究计划提供了一个很好的实践培训平台，为不同群体的本科生和研究生在实验研究的各个方面。该项目的基本概念和结果将被纳入上层物理课程，以突出量子临界在现代凝聚态物理学中的地位。 技术摘要本提案系统地研究了电荷密度波（CDW）和超导性（SC）之间的相互作用，不是在单一化合物（如已充分研究的NbSe 2）中，而是在新型3-4-13锡化物（Ca，Sr）3（Ir 1-xRhx）4Sn 13中。在这些化合物中，通过改变组成，CDW被连续地调谐到结构量子临界点（QCP）。结果与自旋密度波（SDW）与超导性共存的材料，特别是（Ba，K）（Fe，T）2（As，P）2（T=Co，Ni，Rh）进行了比较。在其中一些系统中，超导穹顶下的QCP已经建立。然而，对它们的结构和对疾病的反应的了解有限。具体而言，目前还不清楚QCP对结构点样无序的鲁棒性如何。理论上的预测范围从QCP完全消失，是强大的，甚至稳定的无序。研究涉及结构、热力学和运输测量。特别是，X射线散射，μ子自旋旋转光谱，电气和热运输，伦敦穿透深度，磁化，和弹性电阻率。测量是在温度-成分相图上进行的，强调了正常和超导相中QCP附近的量子临界行为。受控的点状无序引入MeV范围的电子辐照将扰动所研究的系统在固定的化学，电子和磁性配置。正在解决的具体问题是：（1）SC削弱或保护QCP？(2)SC状态下的QCP是否比正常金属中的QCP更能抵抗无序？(3)SC阶段内QCP的通用等级是否与正常状态相同？(4)是否存在与无序相关联的新的涌现现象，例如在QCP附近导致格里菲斯奇点的大的、罕见的区域？该奖项反映了NSF的法定使命，并被认为是值得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的支持。