****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.
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.