Probing Mesoscopic Phenomena in Novel Materials

9624536，PI-Sohn： 拟议的工作涉及探测磁性和有机材料的介观长度尺度的新的，不可预测的量子现象。 提出了两个研究磁性材料中介观现象的方案。 首先，研究铁磁-超导（FS）结中的Andreev反射。 有人预言，由于自旋在Andreev反射中不守恒，铁磁体不具有自旋-旋转对称性，因此在FS界面处将存在不完全Andreev反射。因此，这将影响干净的FS点接触的电导，并导致FS结中的量子干涉效应。第二，互动的数组。将制造尺寸和晶格常数约20 nm的铁磁体点。 磁量子隧穿 量子涨落将在这些阵列中进行研究，以及新颖的集体行为和受控无序效应。 另一个项目是研究叶绿素，一种光子激活的电子转移系统，作为一种生物分子单电子器件。 然而，应该强调的是，后一个项目是探索性的。 * 这项工作的目的是探索新的材料，特别是磁性和有机材料，在介观长度尺度上寻找新的，不可预测的量子现象。 在此之前，磁性和有机材料不能被充分探索介观或量子现象，因为它们的自然长度尺度，亚50纳米，不能很容易地访问。 然而，在纳米纤维技术，包括扫描探针光刻技术的进步，最近允许访问这样小的长度尺度，从而提供了第一次的机会，调查这些新的系统上的介观长度尺度。 一个教育计划，在纳米纤维技术的本科先进的实验室课程的形式， 研究研讨会和实验室实习将与这项拟议的工作交织在一起。 这样的计划将有助于向学生介绍最先进的技术，从而为他们未来的机会做好准备;然而，更重要的是，它将有助于培养学生的分析能力和自信心，这远远超出了课堂。

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.***