z 0

1. Nonlocal effect and microscopic parameters in superconductorsVladimir Kozhevnikov, Tulsa Community College, DMR 0904157 c d e f oxide layer z0 Examples of muon time and field spectra in the normal (a) and superconducting (b) states and of neutron reflectivities (c) and spin asymmetry (d). Sections (e) and (f) present magnetic field profiles in In and Sn, respectively. A core concept of superconductivity is pairing of repealing each other electrons or formation of Cooper pairs. The Cooper pairs have characteristic size x0and an effective mass mcp* reflectingthe coupling strength. Experimental determination of these fundamental microscopic parameters is important for understanding of nature of the electron-electron coupling; it is par-ticularly important for high-temperature superconductors for which physics of the electron pairing is a puzzle. The goal of our project is experimental determination of x0 and mcp*, neither of those have been directly measured in any superconductor. Moreover, it was stated that x0 is unmeasurable. However for a small group of “nonlocal” materials the size and mass of the Cooper pairs can be inferred from a nonlocal effect. Till now thislong ago predicted effectwas not measured because it requires precise measurements of tiny features in a depth profile of magnetic field penetrated into superconductors in the Meissner state. This year we completed measurements of the nonlocal effect performed, for the first time, on In and Sn using low-energy muons and polarized neutrons. The inferred quantities include x0, mcp* and one more key microscopic parameter, a London penetration depth lL. This allowed us to verify experimentally an approach for experimental determination of x0 in any super-conductors, including the high-temperature materials.

2. Nonlocal effect and microscopic parameters in superconductorsVladimir Kozhevnikov, Tulsa Community College, DMR 0904157 Students of TCC Special topics in physics class Cherese Erdovegi, Emily Main and Scott Petty in MIT Plasma science and fusion center (left); Jeffry Healy and Michael Jensen are instructed by Dr. Helmut Fritzsche at NRU nuclear reactor, Chalk River Laboratories (Canada), during experiment with polarized neutrons. Tulsa Community College is a two-years college of primary high education. TCC students involved in the project take a class “Selected topics in physics”. The class meets once a week; each meeting students make presentations on a foremost topic of physics staying beyond the standard curriculum of college physics classes. Students completed the class have their tuition reimbursed from the grant. The most active students participated in the neutron’s experiments in Chalk River Laboratories, Canada, and in the muon’s experiments in Paul Scherrer Institute, Switzerland. The students take part at the APS March Meetings, and at the Oklahoma Research Day conferences (Cameron University, OK). As of today (August/2012) the class has been offered for five semesters; total 17 students graduated the class. Last year the students, who attended the APS March Meeting in Boston, visited The Plasma Science and Fusion Center at MIT. One former student is currently employed in the Science and Math division at TCC, Metro; other students continue their education in STEM specialties at universities of Oklahoma and elsewhere. Articles about this class appeared in TCC news, in The Tulsa World newspaper, in the news of Canadian National Research Council magazine.