Superconductor-(Metal)-Insulator Transitions: Understanding the Emergence of Metallic States, A Continuation Proposal

超导体-（金属）-绝缘体转变：了解金属态的出现，延续提案

• 批准号: 2307132
• 负责人: Aharon Kapitulnik
• 金额: $ 72.76万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2307132&HistoricalAwards=false
• 关键词: Superconductor; Metal; Insulator; Transitions; Understanding

Nontechnical Abstract: An increasing number of recent experiments reveal a possible “anomalous metallic state” (AMS), which exhibits properties that cannot be understood on the basis of “standard paradigms” of electrons in solid-state systems. The project aims to explore the extent of the emergence of the anomalous metallic phase and its relation to a failed superconducting and/or insulating states. Furthermore, the project explores possible variants of the AMS in multiple cases. Results are expected to shed light on a new class of metallic states of matter and will have an impact on physics as a discipline, on education and on society. Pointing to a lack of full understanding of one of the fundamental types of substances in nature, it ought to trigger curiosity at all levels of society, thus helping to enhance our scientific understanding and possible impact technological applications.Technical Abstract: An increasing number of recent experiments on disordered superconducting films, initially searching for a superconductor-insulator transition (SIT), have been pointing to the possibility of a zero-temperature transition from a superconductor to an “anomalous metallic state” (AMS) that features properties of a “failed superconductor.” This state exhibits significant superconducting correlations, yet the system fails to globally condense even at zero temperature, settling at a finite conductivity through a quantum superconductor to metal transition (QSMT). Furthermore, where strongly inhomogeneous systems are studied, charging energy of the superconducting islands, which typically leads to an insulating state through Coulomb blockade, can experience charge fluctuations when weakened, preventing the establishment of a true insulator. As observation of deviations from the “standard paradigm,” particularly in the limit of two-dimensions, have been fast accumulating, it becomes clear that there exists a new class of metallic states as the temperature tends to zero, where the electronic properties cannot remotely be understood on the basis of Fermi liquid and Drude theories, thus pointing to a new paradigm for metallic states in nature. Exploring SIT and the emergence of anomalous metallic states and their properties are the focus of this projects. This is achieved through focus on enhanced phase fluctuations materials either using highly granular films or unconventional superconductors such as superconductor/ferromagnet bilayers, as well as low-temperature magneto-transport measurements including sensitivity to external perturbations and improved mutual-inductance probe for the study of superfluid response.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：最近越来越多的实验揭示了一种可能的“异常金属态”（AMS），它表现出基于固态系统中电子的“标准范式”无法理解的特性。此外，该项目在多种情况下探索了 AMS 的可能变体，预计结果将揭示一类新的金属。它将对物理学作为一门学科、教育和社会产生影响，这表明人们对自然界中基本物质类型之一缺乏充分的了解，这应该会引发社会各个层面的好奇心。有助于增强我们的科学理解和可能影响的技术应用。技术摘要：最近越来越多的无序超导薄膜实验，最初寻找超导体-绝缘体转变（SIT），已指出零温度转变的可能性从一个该状态表现出显着的超导相关性，但该系统即使在零温度下也无法全局凝结，通过量子超导体稳定在有限的电导率此外，在研究强非均匀系统时，超导岛的充电能量通常会通过库仑封锁导致绝缘状态，当被削弱时会经历电荷波动，从而阻止真正绝缘体的建立。随着对“标准范式”的偏差的观察，特别是在二维极限中，已经快速积累，很明显存在一类新的绝缘体。温度为零时的金属态，根据费米液体和德鲁德理论无法远程理解其电子特性，从而为探索自然界中的金属态和异常金属态及其出现提供了一个新的范式。这是通过关注使用高颗粒薄膜或非常规超导体（例如超导体/铁磁体双层）的增强相位波动材料，以及低温磁输运测量（包括对外部扰动的敏感性和改进）来实现的。用于研究超流体响应的互感探针。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进行评估，被认为值得支持标准。