Disordered 3He and Glassy Systems at mK Temperatures

mK 温度下的无序 3He 和玻璃态系统

• 批准号: 0457533
• 负责人: Jeevak Parpia
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0457533&HistoricalAwards=false
• 关键词: Disordered; 3He; Glassy; Systems; mK

This individual investigator award supports an experimental program to investigate disorder in diverse systems at low temperatures. The two systems that will be studied are (i) superfluid 3He in aerogel, where the aerogel introduces correlated disorder and (ii) silica glass at low temperatures where the sound velocity and dissipation provide sensitive probes for the validity of the "standard tunneling model" of disorder in glasses. The project will examine the phase diagram of superfluid 3He for hysteresis in the occurrence of the "A" and "B" phases, for pinning, and for anisotropy in a variety of magnetic fields using ultrasensitive torsion pendulum devices. 4He will also be used to further reduce the volume accessible to the 3He (eventually into isolated "bubble-like" regions, while preserving superfluidity. The experiments on silica glass will use high Q resonators to focus on the very low temperature behavior (below 5mK) where there may be evidence of interactions between tunneling sites, as well as probe the non-linear behavior of these systems. These demanding experiments, which involve cutting edge instrumentation and development of new techniques, provide a challenging environment where graduate and undergraduate students acquire skills (the ability to innovate, initiate, design and carry out) as well as become familiar with analytic and display tools to prepare them for careers in the nation's scientific and technological infrastructure. The research program will also incorporate an undergraduate (year-round) as well as involve a high-school teacher in the research program during the summer. %%%%%3He (unlike all other elements) is in an inherently quantum-mechanical system that does not solidify (unless it is highly compressed) even down to absolute zero. It is one of the purest materials that can be prepared by any means, since at these temperatures, impurities simply freeze out during the procedures required to obtain the liquid state. Eventually 3He attains a highly ordered state - superfluidity, which is different from that attained in most superconductors and its sister isotope 4He. The magnetism of the superfluid atoms means that the atoms pair up together and undergo orbital motion exhibiting different phases or "flavors". All of this behavior is affected by introducing aerogel, a highly dilute glass (also termed solidified smoke) whose structure is so small that it penetrates into the superfluid pairs, altering the occurrence (and perhaps even the character) of the "flavors" of superfluid that appear. The research will look for changes under a variety of conditions, including when the helium is confined to small "bubbles". A second area probes our understanding of the properties of a standard glass at low temperatures, where one imagines that order is imposed by the absence of thermal excitations. However, the glass exhibits quantum characteristics, where atoms tunnel from one configuration to another, affecting the sound propagation qualities. By carrying out precise measurements on these systems the research will add to our understanding of the role of disorder under less extreme conditions. Besides adding to the understanding of quantum systems, this research provides a demanding experimental environment that educates and trains graduate and undergraduate students (and will also create a positive impact by involving a science teacher into the summer research program) for successful careers in the nation's scientific and technological infrastructure.

该个体研究者奖支持一个实验计划，以调查低温下各种系统中的疾病。将研究的两个系统是（i）气凝胶中的超氟3He，气凝胶在低温下引入相关性疾病和（ii）硅胶玻璃，在低温下，声速和耗散为玻璃中疾病的“标准隧道模型”的有效性提供了敏感的探针。该项目将在“ A”和“ B”阶段的发生中检查超流体3HE的相图，用于固定，用于固定，以及使用超敏感性扭转摆动器的各种磁场中的各向异性。 4E还将用于进一步减少3HE可以访问的体积（最终分为孤立的“泡泡状”区域，同时保留超流量。硅胶玻璃上的实验将使用高Q共振器来集中在非常低的温度行为上（低于5MK），在5MK以下）可能会在其中有涉及这些隧道的相互作用的证据，以及这些隧道的发展涉及这些不断的系统，这些系统涉及这些构成这些系统的行为。新技术，提供一个充满挑战的环境，毕业和本科生获得了创新，启动，设计和执行的能力，并熟悉分析和展示工具，以使其在美国科学和技术基础设施中的职业做好准备其他元素）是在固有的量子力学系统中，该系统甚至无法固化（除非高度压缩），甚至可以降低到绝对零。它是可以通过任何方式制备的最纯粹的材料之一，因为在这些温度下，杂质在获得液态所需的过程中简单地冻结了。最终，3E达到了高度有序的状态 - 超流量，这与大多数超导体及其姐妹同位素4HE的达到不同。超流体原子的磁性意味着原子搭配在一起，并经历轨道运动，表现出不同的相或“风味”。所有这些行为都受到引入气门的影响，气凝胶是一种高度稀释的玻璃（也称为凝固的烟雾），其结构很小，以至于它渗入超级流体对，从而改变了出现的超级流体的“风味”的发生（甚至是特征）。该研究将在各种条件下寻找变化，包括氦气局限于小“气泡”。第二个区域探究了我们对低温下标准玻璃特性的理解，在这种情况下，人们想象的是，由于没有热激发而施加了秩序。但是，玻璃表现出量子特性，其中原子隧道从一种构型到另一种构型，影响声音传播质量。通过对这些系统进行精确的测量，研究将增加我们对疾病在不太极端条件下的作用的理解。除了增加对量子系统的理解外，这项研究还提供了一个苛刻的实验环境，该环境对毕业生和本科生进行教育和培训（这也将通过使科学教师参与夏季研究计划来创造积极的影响），以实现该国科学和技术基础设施的成功职业。