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

共存 Bose

• 批准号: 0202113
• 负责人: Jeevak Parpia
• 金额: $ 39万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0202113&HistoricalAwards=false
• 关键词: Coexisting; Bose; Fermi; Superfluids; Liquid

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.

这个低温物理项目将研究气凝胶中3He以及3He和4He的相分离混合物的行为。气凝胶，一种占体积0.1%至3%的稀释玻璃，是唯一可以将结构“无序”引入3He的方法。其中一个项目将研究在这种无序的超流体中的流动和耗散的开始（超流的崩溃）。磁共振将被用来表征孤立的“气泡”的超流的同位素混合物中捕获的超流3He。这将建立可能限制超流性的尺寸约束。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，使他们能够获得技能和分析工具，为国家科学和技术基础设施的职业生涯做好准备。液态3He仅在接近“绝对零度”时可用，是可以通过任何方式制备的最纯净的材料之一。 杂质在获得液体所需的艰苦冷却和液化过程中简单地冻结出来。 像它更丰富的姊妹同位素4He一样，3He可以在“超流体”状态下获得。 但是超流体由于3He原子的磁性而变得复杂，每个原子都像一个微小的指南针。 原子本身经历相互的轨道运动，它们的罗盘针以各种方式配对，这取决于原子的轨道运动。 由于其复杂的磁性特征，3He的超流体性质是基本的兴趣，并且在某些情况下可以与更常见的现象有关，例如电子在电线中的流动。 该奖项下的一个项目将研究超纯超流3He在通过添加气凝胶稀释和“无序”时如何变化，气凝胶是一种稀释的玻璃，占容器总体积的不到2%。 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性。 这项研究还将寻找当氦被限制在小“气泡”中时配对的变化，这些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的影响将被检查的目的是检测能量耗散，类似于加热的电线电流。 这是超流性丧失的信号。 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，教育和培训研究生和博士后研究人员，使他们在国家的科学和技术基础设施中取得成功。