Mesoscopic Magnetic Measurements

技术上，小于消相干长度的正常金属环应该具有持续的电流，该电流在流过环的磁通中是周期性的。这种持续电流是电子系统中相位相干性的标志，并提供了一种检验电子态模型和理论的手段。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(其中电子的平均自由程与周长相当)，并直接测量名义上相同的环中的电流分布。这一分布将提供有关量子金属中无序和相互作用的作用的信息。扫描方法允许测量每个冷却过程中多个介观样品的性质，一次测量一个样品。这些要求极高的实验将在知识丰富的研究环境中培养一些国家顶尖的青年科学家--S。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，实验室人员通过中学教师暑期研究所与K-12科学教育界积极互动。非技术众所周知，超导环中的电流可以无限流动，因为超导体的电阻为零。这样的洋流叫什么？持久？洋流。不太为人所知的是，正常金属--即使它们是阻性的--在理论上也会有持续的电流，当它们足够小和足够冷的时候。这些持续的电流是金属中电子的量子力学、波状性质的直接标志，并提供了一种测试电子态模型和理论的手段。该项目将在极低的温度下使用一种名为超导量子干涉装置(SQUID)的超灵敏磁性探测器来研究持续电流，以测试我们对金属和半导体的量子力学性质的理解。这些要求极高的实验将在知识丰富的研究环境中培养一些国家顶尖的青年科学家--S。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，实验室人员通过中学教师暑期学院与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.