Nonlocal Electrodynamics Effect and Microscopic Intrinsic Parameters in Pippard Superconductors. Experimental Study

****非技术摘要****超导是科学认识和应用中最重要的现象之一。科学家们在近100年前发现了这一现象，花了40多年的时间才对这一现象有了大致的了解。不久之后，超导的实际应用开始出现。也许，其中最著名的是磁共振成像。自1986年以来，物理学家面临着一个新的挑战，那就是非常规超导体的发现，它打破了传统的认识。超导理论的基本概念是库珀对，准粒子的形成。由两个电子组成的无电阻传输电流的（超电流）。库柏对的尺寸是一千个原子大小的数量级一对？S的质量大约是电子的2.5倍。了解这些参数对理论和实际应用都很重要。令人惊讶的是，这些关键特性的实验值还没有在任何超导体中被实验确定。这个个人研究者奖支持一个项目，其目标是测量传统超导体中库珀对的大小和质量。实验将使用凝聚态物理中最先进的核技术进行。社区大学生的直接参与构成了这个项目的主要教育价值。****技术摘要****超导体的主要微观本征参数是零度下的伦敦穿透深度和皮帕德相干长度，对超导理论和实际应用都很重要。迄今为止，这些参数的实验值还没有为任何超导体建立起来。该个人研究者奖支持直接测量经典Pippard（极端i型）超导体（特别是Al， in和Sn）的伦敦穿透深度和Pippard相干长度的项目。考虑到Pippard相干长度代表Cooper对的大小，而伦敦穿透深度与准粒子的质量有关，该项目的目标是获得指定材料Cooper对这些关键特征的实验值。从迈斯纳态穿透超导体的磁场分布中可以得到微观本征参数的值。磁场剖面将使用极化中子反射仪、低能介子自旋旋转光谱和β探测核磁共振技术进行测量。社区大学生的直接参与构成了这个项目的主要教育价值。

****NON-TECHNICAL ABSTRACT****Superconductivity is one of the most striking phenomena of consequence for scientific understanding and applications. Discovered nearly one hundred years ago, it took scientists more than four decades to achieve a general understanding of this phenomenon. Soon after, practical applications of superconductivity began emerging. Probably, the most well-known of those is Magnetic Resonance Imaging. Since 1986 physicists have faced a new challenge, the discovery of unconventional superconductors, which defied conventional understanding. The basic concept of superconductivity theory is the formation of Cooper pairs, ?quasiparticles? consisting of two-electrons that transport current without resistance (a supercurrent). The dimension of a Cooper pair is of the order of a thousand atomic sizes and a pair?s mass is about 2.5 times that of an electron. Knowledge of these parameters is important both for the theory and for practical applications. Surprisingly enough, experimental values of these key characteristics have not yet been experimentally established for any superconductor. This individual investigator award supports a project which goal is to measure the size and the mass of the Cooper pairs in conventional superconductors. The experiments will be performed using the most advanced nuclear techniques of condensed matter physics. Direct involvement of community college students constitutes a major educational merit of this project. ****TECHNICAL ABSTRACT****The principal microscopic intrinsic parameters of superconductors, important for both superconductivity theory and for practical applications, are the London penetration depth at zero temperature and the Pippard coherence length. To date the experimental values of these parameters have not been established for any superconductor. This individual investigator award supports a project to directly measure the London penetration depth and the Pippard coherence length in classical Pippard (extreme Type-I) superconductors, specifically in Al, In and Sn. Taking into account that the Pippard coherence length represents the size of the Cooper pairs and the London penetration depth is associated with the mass of the quasiparticles, the project is targeted at obtaining experimental values of these key characteristics of the Cooper pairs for the indicated materials. Values of the microscopic intrinsic parameters will be obtained from the profile of the magnetic field penetrating into the superconductors in the Meissner state. The magnetic field profiles will be measured using polarized neutron reflectometry, low-energy muon spin rotation spectroscopy and beta-detected NMR techniques. Direct involvement of community college students constitutes a major educational merit of this project.