Experiments on Superfluid 3He in Bulk and in Aerogel

本研究主要研究气凝胶中超流3He的性质。气凝胶中超流3He相图的新领域将被探索。这种气凝胶可能提供将受控无序引入液体中以创建新的物理系统的可能性。康奈尔大学的一个项目将测量超流体转变附近气凝胶中3He的比热。康奈尔大学的另一个项目将研究在特定的场梯度条件下，在纯3He中的相干自旋进动，从而产生长寿命的均匀进动模式。莫斯科Kapitza研究所的一项合作将研究在气凝胶中稳定3He的B相的可行性，以及探索无序存在时的自旋动力学。在特拉华州，合作的重点将是探索新的定制气凝胶的可行性，这种气凝胶具有不同于在基本条件下生长的气凝胶的相关性。特拉华州的研究小组还将研究对气凝胶进行单轴压缩以改变密度并提供进入气凝胶的首选方向的可行性。俄亥俄州立大学的研究小组和卡皮扎研究所的研究人员将为这些活动提供理论支持。参与该项目的研究生和博士后将接触到敏感信号检测和恢复技术、大型项目设计和管理以及全面接触数据采集和管理。我们与俄罗斯同事在研究方面的大量参与将提供国际视角，并建立对整个科学界重要的长期合作关系。我们的培训将为学生和博士后为学术、技术和管理职业生涯做准备。这项工作是针对无序存在下的超流3He的研究。虽然通常情况下，超流3He是地球上最纯净的物质，并且不支持无序或杂质，但我们发现，引入稀薄的纳米级结构二氧化硅玻璃后，超流体的性质可以以一种明确的方式改变。将在伊萨卡的康奈尔大学、特拉华大学、俄亥俄州立大学和莫斯科的卡皮扎研究所开展的这一项目将探讨相图的变化，包括支持新型磁(自旋)传输机制的能力。该小组将开发和使用新的磁成像和声波技术，并在超低温下进行敏感测量。这项研究应该提供关于一类潜在的新的三维量子相变的信息(量子相变是指临界点附近的波动是量子的，而不是热的，量子相变被认为与早期宇宙有关)，以及自旋在无序材料界面上的传输，这是一个相当重要的技术问题。该项目的学生和博士后助理在物理学、信号恢复、数据采集和管理以及项目集成方面接受严格的培训，可以从事学术或工业科学方面的职业。我们合作的国际方面也为人力资源提供了独特的潜力。

This research is focused on the investigation of the properties of superfluid 3He in Aerogel. New areas of the phase diagram of superfluid 3He in aerogel will be explored. The Aerogel may potentially offer the possibility of introducing controlled disorder into the liquid to create new physical systems. One project at Cornell will measure the specific heat of 3He in aerogel near the superfluid transition. Another Cornell project will study coherent spin precession in pure 3He under specific field gradient conditions that yield a long-lived homogenous precession mode. A collaboration at the Kapitza Institute in Moscow will examine the feasibility of stabilizing the B phase of 3He in Aerogel, as well as explore the spin dynamics in the presence of disorder. At Delaware, the collaboration will focus on exploring the feasibility of new tailor made aerogels, having correlations that are different from those grown under basic conditions. The Delaware group will also examine the feasibility of subjecting the aerogel to uniaxial compression to alter the density and provide a preferred direction into the aerogel. Theoretical support for these activities will be provided by the group at the Ohio State University and by researchers at the Kapitza Institute. Graduate students and post-doctoral associates involved in this project will be exposed to sensitive signal detection and recovery technology, large scale project design and management as well as a thorough exposure to data acquisition and management. Our substantial involvement in research with colleagues in Russia will provide International perspectives and establish long-term collaborations that are important for the scientific community as a whole. Our training will prepare students and post-docs for academic, technical, and management careers. This work is directed at the study of the superfluid 3He in the presence of disorder. While ordinarily, superfluid 3He is the purest material on earth and supports no disorder or impurities, we have found that the introduction of a dilute nanometer scale structured silica glass allows the properties of the superfluid to be altered in a well-defined way. The changes to the phase diagram, including the ability to support new types of magnetic (spin) transport mechanisms will be explored in this project which is to be carried out at Cornell University in Ithaca, the University of Delaware, the Ohio State University, and at the Kapitza Institute in Moscow. The group will develop and use new magnetic imaging and sonic techniques, and carry out sensitive measurements at ultra-low temperatures. The research should provide information on a potentially new class of three dimensional quantum phase transitions (a quantum phase transition is one in which the fluctuations near the critical point are quantum and not thermal in nature, and quantum phase transitions are thought to be related to the early universe) as well as the transport of spins across interfaces in disordered materials, a problem of considerable technological importance. Students and Post-Doctoral Associates in this program receive rigorous training in physics, signal recovery, data acquisition and management as well as project integration, and can pursue careers in either academic or industrial science. The International aspect of our collaboration also offers unique potential for human resources.