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

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），它表现出无法根据固态系统中电子的“标准范式”来理解的性质。该项目旨在探索异常金属相出现的程度及其与失败的超导和/或绝缘状态的关系。此外，该项目还探讨了AMS在多种情况下的可能变体。预计结果将揭示一类新的物质金属态，并将对物理学作为一门学科、教育和社会产生影响。指出缺乏充分了解的基本类型的物质在自然界中，它应该引发好奇心在社会各个层面，从而有助于提高我们的科学理解和可能的影响技术应用。技术摘要：最近越来越多的无序超导薄膜实验，最初是为了寻找超导体-绝缘体转变（SIT），一直在指出从超导体到“异常金属态”（AMS）的零温度转变的可能性，这种转变具有“失效超导体”的特性。这种状态表现出显着的超导相关性，但即使在零温度下，系统也无法全局凝聚，通过量子超导体到金属过渡（QSMT）以有限的电导率稳定下来。此外，在研究强非均匀系统的情况下，超导岛的充电能量（通常通过库仑阻塞导致绝缘状态）在减弱时可能会经历电荷波动，从而防止建立真正的绝缘体。随着对偏离“标准范式”的观察，特别是在二维极限下，已经迅速积累，很明显，当温度趋于零时，存在一类新的金属态，其中的电子性质不能根据费米液体和德鲁德理论来理解，从而指出了自然界中金属态的新范式。探索SIT和异常金属态的出现及其性质是该项目的重点。这是通过关注增强相位波动材料来实现的，这些材料使用高度颗粒状的薄膜或非常规的超导体，例如超导体/铁磁双层，以及低温磁输运测量，包括对外部扰动的灵敏度和改进的互-该奖项反映了NSF的法定使命，并已被认为是值得通过使用评估的支持，基金会的学术价值和更广泛的影响评审标准。

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.