Mesoscopic Magnetic Measurements

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*******Technical Abstract*******This individual investigator award will support the use of a dilution-refrigerator-based scanning Superconducting QUantum Interference Device (SQUID) to make direct magnetic measurements of mesoscopic normal metal rings. Persistent currents in normal metal rings should exist as a result of quantum-mechanical phase coherence around the ring and have been extensively studied theoretically. However, only one study measured single diffusive rings, presumably because of the difficulty of measuring the small signal from a single mesoscopic sample. The PI and her students propose to study these systems with a scanning SQUID, which will enable measurement of the properties of many mesoscopic samples, one sample at a time, in each cooldown, providing much-needed experimental input on some of the profound theoretical results of mesoscopics theory. These highly demanding experiments will provide the direct educational benefit of training some of the nation's top young scientists in an intellectually rich research environment. Undergraduate and graduate research students will learn nanotechnology and precision measurement techniques as well as fundamental physics. *******Nontechnical abstract*******Mesoscopic physics is the study of materials and devices that are sufficiently small for quantum-mechanical effects to be important. Direct magnetic measurements on single samples are important, but rare, because the magnetic signal is weak. Superconducting QUantum Interference Devices (SQUIDs) are arguably the world's most sensitive magnetic detectors. This award will support the use of an unusual low-temperature SQUID to make direct magnetic measurements of some of the most striking predictions of the quantum-mechanical theory of metals. The scanning approach employed in this work will provide experimental input on some of the profound theoretical results of mesoscopics theory. Beyond its own intellectual merit, this work will support and enhance the nation's scientific infrastructure through the maintenance of a very unusual scanning SQUID microscope which is also used collaboratively with other investigators of novel materials. These highly demanding experiments will provide the direct educational benefit of training some of the nation's top young scientists in an intellectually rich research environment. Undergraduate and graduate research students will learn nanotechnology and precision measurement techniques as well as fundamental physics.