Probing Mesoscopic Phenomena in Novel Materials

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9624536, PI-Sohn: The proposed work involves probing magnetic and organic materials ol the mesoscopic length scale for new, unpredicted quantum phenomena. Two projects dealing with mesoscopic phenomena in magnetic materials are proposed. First, Andreev reflection in ferromagnet-superconductor (FS) junctions will be investigated. It has been predicted that because spin is not conserved in Andreev reflection and because ferromagnets do not have spin- rotation symmetry, there will be incomplete Andreev reflection at the FS interface. As such, this will influence the conductance of clean FS point contacts and lead to quanturn-interference effects in FS junctions. Second, arrays of interacting. ferromagnet dots of size and lattice constant ~20nm will be fabricated. The interplay between magnetic quantum tunneling and quantum fluctuations will be investigated in these arrays, as will novel collective behavior and controlled-disorder effects. An additional project, investigating chlorophyll, a photon-activated electron-transfer system, as a biomolecular single electronics device will be explored. It should be mphasized, however, that this latter project is exploratory. ***The work proposed aims to probe novel materials, in particular magnetic and organic materials, on the mesoscopic length scale for new, unpredicted quantum phenomena. Previously, magnetic and organic materials could not be fully explored for mesoscopic or quantum phenomena because their natural length scales, sub-fifty nanometer, could not be easily accessed. However, advances in nanofabrication technology, including scanning probe lithography, have recently allowed access to such small length scales, thus providing for the very first time the opportunity to investigate these novel systems on the mesoscopic length scales. An educational program, in the form of an undergraduate advanced laboratory course on nanofabrication technology, research seminars, and laboratory internships, will be developed and interwoven with this proposed work. Such a program will serve to introduce students to state-of-the-art technology, thus preparing them for future opportunities; more importantly, however, it will serve to develop students' analytical skills and self-confidence which go well beyond the classroom.***