Coexisting Bose & Fermi Superfluids and Fermi Liquid Transport in the Presence of Disorder

这个低温物理项目将研究3He以及3He和4He相分离混合物在气凝胶中的行为。气凝胶是一种稀释的玻璃，占体积的0.1%到3%，是唯一一种可以将结构“无序”引入3He的方法。一个项目将研究这种无序超流体中的流动和耗散的开始（超流体的分解）。磁共振将被用来表征被困在同位素混合物中的超流体3He的孤立“气泡”的超流动性。这将建立可能限制超流动性的尺寸约束。这些要求苛刻的实验，涉及尖端仪器和新技术的开发，提供了一个具有挑战性的环境，研究生和博士后研究人员获得技能和分析工具，为他们在国家科学和技术基础设施的职业生涯做好准备。液态氦只能在“绝对零度”附近获得，它是可以用任何方法制备的最纯净的材料之一。在获得液体所需的艰苦的冷却和液化过程中，杂质只是被冻结掉。像其更丰富的姊妹同位素4He一样，3He可以在“超流体”状态下获得。但3He原子的磁性使超流体变得复杂，每个原子都像一个小指南针。原子本身进行相互的轨道运动，它们的罗盘针根据原子的轨道运动以不同的方式配对。由于其复杂的磁性，3He的超流体性质引起了人们的基本兴趣，在某些情况下，它可以与更常见的现象有关，比如电子在导线中的流动。该奖项下的一个项目将研究超纯超流体3He在加入气凝胶（一种占容器总体积不到2%的稀释玻璃）稀释和“无序”时是如何变化的。引入氦的无序改变了“成对”原子的轨道运动，在某些温度和压力条件下可以完全破坏超流动性。该研究还将寻找当氦被限制在小“气泡”中时的配对变化，这些小“气泡”近似于所谓的零维超流体“点”。最后，流体流动对无序超流体的影响将被考察，目的是检测能量耗散，类似于电流加热导线。这是以超流动性的丧失为标志的。除了增加对量子系统和超流体流动的理解外，这项研究还提供了一个苛刻的实验环境，为研究生和博士后研究人员在国家科学和技术基础设施领域的成功事业提供教育和培训。

This low temperature physics project will investigate the behavior of 3He, and phase-separated mixtures of 3He and 4He, in Aerogel. Aerogel, a dilute glass that occupies between 0.1% and 3% of the volume is the only means by which a structural "disorder" can be introduced to the 3He. One project will examine flow and the onset of dissipation (the breakdown of superfluidity) in this disordered superfluid. Magnetic resonance will be used to characterize the superfluidity of isolated "bubbles" of superfluid 3He trapped in the isotope mixtures. This will establish dimensional constraints that may limit superfluidity. These demanding experiments, which involve cutting edge instrumentation and development of new techniques, provide a challenging environment where graduate students and post-doctoral researchers acquire skills and analytic tools to prepare them for careers in the Nation's scientific and technological infrastructure.Liquid 3He, available only near "absolute zero" is one of the purest materials that can be prepared by any means. Impurities simply freeze out during the arduous cooling and liquefaction procedures required to obtain the liquid. Like its more abundant sister isotope 4He, 3He can be obtained in a "superfluid" state. But the superfluid is complicated by the magnetism of the 3He atoms, each of which acts like a tiny compass needle. The atoms themselves undergo mutual orbital motion, and their compass needles pair up in various ways depending on the orbital motion of the atoms. Because of its complex magnetic character, the superfluid properties of 3He are of fundamental interest, and in some circumstances can be related to more common phenomena like the flow of electrons in a wire. One project under this award will study how the ultra pure superfluid 3He changes when it is diluted and 'disordered' by the addition of Aerogel, a dilute glass that occupies less than 2% of the total volume of the container. The disorder introduced into the helium changes the orbital motions of 'paired' atoms, and in some conditions of temperature and pressure can destroy superfluidity altogether. The research will also look for changes in the pairing when the helium is confined to small "bubbles", which approximate a so-called zero-dimensional superfluid "dot". Finally the effects of fluid flow on the disordered superfluid will be examined with the objective of detecting energy dissipation, analogous to heating of a wire by current flow. This is signaled by loss of superfluidity. Besides adding to the understanding of quantum systems and superfluid flow, this research provides a demanding experimental environment that educates and trains graduate students and post-doctoral researchers for successful careers in the Nation's scientific and technological infrastructure.