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3HE和3HE和4HE的3HE的行为。气凝胶是一种占地0.1％至3％的稀玻璃，是唯一可以将结构“疾病”引入3HE的手段。一个项目将检查这种无序超流体的流动和耗散的发作（超流体的崩溃）。磁共振将用于表征被困在同位素混合物中的超氟3e的隔离“气泡”的超流体。这将建立可能限制超流量的维度约束。这些苛刻的实验涉及最先进的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了技能和分析工具，以使其为国家科学和技术基础架构的职业做好准备。3He，仅在“绝对Zero”附近可用的“ Absolute Zero”，这是可以通过任何手段准备的纯粹材料之一。 在获得液体所需的艰苦冷却和液化过程中，杂质只需冻结。 就像它更丰富的姐妹同位素4He一样，可以在“超流体”状态下获得3HE。 但是，超流体的3he原子的磁性使每个原子的磁性变得复杂，每种原子的作用都像是小指南针。 原子本身会经历相互的轨道运动，其指南针针头根据原子的轨道运动来搭配。 由于其复杂的磁性特征，3HE的超流体特性具有根本性的兴趣，在某些情况下可能与更常见的现象有关，例如电线中电子的流动。 该奖项下的一个项目将研究超纯的超级流体3HE在稀释和“无序”的添加气凝胶时如何变化，这是一种稀释玻璃，稀释玻璃不到容器总体积的不到2％。 引入氦气的疾病会改变“配对”原子的轨道运动，在某些条件下，温度和压力会完全破坏超流体。 当氦气局限于小的“气泡”时，该研究还将寻找配对的变化，该氦气近似于所谓的零维超流体“点”。 最后，将检查流体流对无序超流体的影响，目的是检测能量耗散，类似于电流流量加热电线。 这是通过丧失超流体的信号。 除了增加对量子系统和超流量流的理解外，这项研究还提供了一个苛刻的实验环境，该环境向研究生和博士后研究人员培训了该国科学和技术基础设施的成功职业。