Mesoscopic Magnetic Measurements

从技术上讲，小于退相干长度的普通金属环预计具有持续电流，该电流在通过环的通量中是周期性的。这种持续电流是电子系统中相位相干性的标志，并为测试电子状态的模型和理论提供了一种手段。该项目将在稀释冰箱中使用扫描超导量子干涉装置（SQUID）显微镜来研究弹道金属环（其中电子平均自由程与周长相当），并直接测量名义上相同的环集合中的电流分布。这种分布将提供量子金属中无序和相互作用的信息。扫描方法允许在每次冷却中测量许多介观样品的性质，一次一个样品。这些高要求的实验将提供教育效益的培训一些国家？美国顶尖的年轻科学家在一个智力丰富的研究环境。研究生将学习纳米技术和精密测量技术以及基础物理。此外，实验室人员通过暑期中学教师学院与K-12科学教育界积极互动。众所周知，超导环中的电流可以无限流动，因为超导体的电阻为零。这种电流被称为“持续电流”。电流。不太为人所知的是，普通金属虽然具有电阻性，但在足够小且足够冷的情况下，理论上也有望具有持续电流。这些持续的电流是量子力学的直接标志，金属中电子的波状性质，并提供了一种测试电子状态模型和理论的方法。该项目将使用一种超灵敏的磁探测器，称为超导量子干涉装置（SQUID），在极低的温度下研究持续电流，以测试我们对金属和半导体量子力学性质的理解。这些高要求的实验将提供教育效益的培训一些国家？美国顶尖的年轻科学家在一个智力丰富的研究环境。研究生将学习纳米技术和精密测量技术以及基础物理。此外，实验室人员通过暑期中学教师学院与K-12科学教育界积极互动。

TechnicalA normal metal ring that is smaller than the decoherence length is expected to have a persistent current that is periodic in the flux through the ring. Such a persistent current is a signature of phase coherence in an electronic system, and provides a means to test models and theories of the electronic state. This project will use a scanning Superconducting QUantum Interference Device (SQUID) microscope in a dilution refrigerator to study ballistic metal rings (in which the electron mean free path is comparable to the circumference) and to directly measure the distribution of currents in an ensemble of nominally identical rings. This distribution will provide information on the role of disorder and interactions in quantum metals. The scanning approach allows the measurement of the properties of many mesoscopic samples in each cooldown, one sample at a time. These highly demanding experiments will provide the educational benefit of training some of the nation?s top young scientists in an intellectually rich research environment. Research students will learn nanotechnology and precision measurement techniques as well as fundamental physics. In addition, lab personnel interact actively with the K-12 science education community through a Summer Institute for Middle School Teachers.Non-technicalIt is well known that currents in superconducting rings can flow indefinitely because superconductors have zero resistance. Such currents are called ?persistent? currents. Less well known is that normal metals -- even though they are resistive -- are also theoretically expected to have persistent currents when they are sufficiently small and cold. These persistent currents are a direct signature of the quantum mechanical, wavelike nature of the electrons in the metal, and provides a means to test models and theories of the electronic state. This project will use an ultrasensitive magnetic detector, called a Superconducting QUantum Interference Device (SQUID), at very low temperatures to study persistent currents in order to test our understanding of the quantum-mechanical nature of metals and semiconductors. These highly demanding experiments will provide the educational benefit of training some of the nation?s top young scientists in an intellectually rich research environment. Research students will learn nanotechnology and precision measurement techniques as well as fundamental physics. In addition, lab personnel interact actively with the K-12 science education community through a Summer Institute for Middle School Teachers.