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以及气凝胶中3He和4He的相分离混合物的行为。气凝胶是一种稀薄玻璃，占体积的0.1%到3%，是向3He引入结构“无序”的唯一方法。其中一个项目将研究这种无序超流体中的流动和耗散的开始(超流性的破裂)。核磁共振将被用来表征被困在同位素混合物中的孤立的超流3He气泡的超流性。这将建立可能限制过剩流动性的尺寸约束。这些要求苛刻的实验涉及尖端仪器和新技术的开发，为研究生和博士后研究人员提供了一个具有挑战性的环境，让他们获得技能和分析工具，为在国家科学和技术基础设施的职业生涯做好准备。液体3He，只能在“绝对零度”附近获得，是任何方法都可以制备的最纯的材料之一。杂质只是在获得液体所需的艰苦的冷却和液化过程中冻结。与其更丰富的姊妹同位素4He一样，3He也可以在“超流体”状态下获得。但超流体由于3He原子的磁性而变得复杂，每个原子的作用都像一个微小的指南针。原子本身经历了相互的轨道运动，它们的指南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的超流体性质具有根本的意义，在某些情况下，可能与更常见的现象有关，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在加入气凝胶时会发生怎样的变化。气凝胶是一种稀释玻璃，占容器总体积的不到2%。氦中引入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，可以完全摧毁超流性。这项研究还将寻找当氦被限制在小的“气泡”中时，配对的变化，这些小气泡近似于所谓的零维超流体“点”。最后，将考察流体流动对无序超流体的影响，目的是检测能量耗散，类似于电流加热导线。过剩流动性的丧失表明了这一点。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要求苛刻的实验环境，教育和培训研究生和博士后研究人员，以便在国家的科学和技术基础设施中成功地从事职业生涯。

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.