Coherent Thermal and Electrical Transport in Mesoscopic Structures

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*****NON-TECHNICAL ABSTRACT******The increasing miniaturization of electronic circuitry that allows the development of faster computers and slimmer cell phones is presently facing two questions: what impediments are there to making today's technology even smaller? and can fundamentally new types of devices, based on quantum effects, be manufactured? This individual investigator award supports a project that will address both of these questions. One of the biggest obstacles to shrinking current devices is that as computer chips get smaller and smaller they heat up more and more. In addressing this problem the proposed research will attempt to understand the basic physics behind heat conduction for wires that are on the nanometer scale, which appears to differ from heat conduction in larger wires. This research will advance the drive towards fundamentally new types of devices by looking at the interplay between different materials on size scales small enough that the quantum interactions between these materials yield new physical effects that could be harnessed for future technologies. In addition to training graduate students and post-docs, this project will train undergraduates and high school students in basic techniques for making objects on the micro- and nanoscales.*****TECHNICAL ABSTRACT******This individual investigator award supports a project exploring the electrical and thermal properties of metallic, mesoscopic heterostructures composed of superconducting (S), normal-metal (N), and ferromagnetic (F) materials. The electrical transport experiments will examine a broad array of coherent processes caused by proximity effects between the materials. These experiments will include investigations into triplet superconductivity in FSF devices, non-local Andreev reflection in NSN and FSF devices, and tunable pi-junctions in SNS devices. The thermal transport experiments will pursue prior observations of anomalous behavior in nanoscale structures, including possible deviations from the Wiedemann-Franz law in normal-metal wires and unexplained symmetries in the thermopower of Andreev interferometers. While the most critical fabrication steps and milliKelvin temperature measurements of these devices will be undertaken by graduate students and post-docs, some nano- and microfabrication steps will be performed by undergraduate and local high school students, training them in the basics of e-beam and photolithography.