Materials World Network: Nearly Two Dimensional 3He- A New Model Quantum System

材料世界网：近二维3He——一种新模型量子系统

• 批准号: 0806629
• 负责人: Jeevak Parpia
• 金额: $ 54万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0806629&HistoricalAwards=false
• 关键词: Materials; World; Network; Nearly; Two

Technical AbstractThis Materials World Network award by the Division of Materials Research supports a three-year experimental program to investigate how reducing the dimensionality of 3He leads to novel p-wave order parameters when this unconventionally paired superfluid is confined to a length comparable to the coherence length. In contrast to metallic systems, 3He has a spherical Fermi surface; yet anisotropic paired states emerge from the isotropic normal liquid. Confinement of 3He in small geometries is expected to modify this behavior. It has been theoretically predicted that confined superfluid 3He will exhibit broken translational symmetry en route to the destruction of superfluidity. Dimensional constraints might also promote the stability of competing phases that are not manifest in the bulk. The technology to fabricate confining geometries with well characterized surfaces that can be patterned to achieve specified roughness has been developed at Cornell University. The roughness will affect the resulting phases via their stability and response to disorder ? an important feature that has implications for the broader relevance of this work to Condensed Matter Physics. Patterning to introduce periodicity and test the robustness of emerging phases of confined 3He against periodicity is also planned. We will also construct and use high precision flow cells to examine flow of 4He, 3He doped 4He films and eventually superfluid 3He in nanoporous media. These demanding experiments, which require 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 be integrated with partner programs at Royal Holloway University of London and Manchester University. Graduate students will have the opportunity to work with their counterparts by spending a semester in the UK and by hosting counterparts at Cornell. The research program will also incorporate an undergraduate student throughout the award period.Non-Technical AbstractHelium (unlike all other elements) is inherently quantum-mechanical and does not solidify (unless compressed) even down to absolute zero temperature. 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. These behaviors are affected by confining 3He within precisely characterized geometries that effectively alter the dimensionality of the 3He. By carrying out precise measurements on these systems the research will add to our understanding of the role of confinement under less extreme conditions. The program will also prepare graduate students for an increasingly international scientific and technological environment by embedding them in (and allowing them to host students from) counterpart laboratories that use different techniques to probe the same systems. Besides adding to the understanding of quantum systems, this research provides a demanding experimental environment that educates and trains graduate and undergraduate students for successful careers in the Nation's scientific and technological infrastructure. In addition, this research program will also create a positive impact on future science and technology workforce by involving a science teacher in this research during summer.

由材料研究部颁发的材料世界网络奖支持了一项为期三年的实验计划，该计划旨在研究当这种非常规配对超流体被限制在与相干长度相当的长度时，降低3He的维数如何导致新的p波阶参数。与金属体系相比，3He具有球形费米表面；而各向异性的偶态则出现在各向同性的正常液体中。在小几何结构中限制3He有望改变这种行为。理论上已经预测，受限超流体3He在破坏超流体的过程中将表现出破碎的平移对称性。尺寸限制也可能促进竞争相的稳定性，而这些相在体中不表现出来。康奈尔大学（Cornell University）开发了一种制造具有良好特征表面的限制几何形状的技术，该技术可以通过图案来达到指定的粗糙度。粗糙度将通过相的稳定性和对无序的响应来影响相。这是一个重要的特征，对这项工作与凝聚态物理的广泛相关性有影响。还计划了引入周期性和测试约束3He的新兴相位对周期性的鲁棒性的图案。我们还将构建和使用高精度流动池来检测4He， 3He掺杂4He薄膜和最终超流3He在纳米多孔介质中的流动。这些要求苛刻的实验需要开发新技术，为研究生和本科生获得技能（创新、发起、设计和实施的能力）以及熟悉分析和展示工具提供了一个具有挑战性的环境，为他们在国家科学和技术基础设施的职业生涯做好准备。该研究项目将与伦敦皇家霍洛威大学和曼彻斯特大学的合作项目整合。研究生将有机会在英国度过一个学期，并在康奈尔大学接待他们的同行。该研究项目还将包括一名本科生在整个奖励期间。与所有其他元素不同的是，铥本质上是量子力学的，即使降到绝对零度也不会凝固（除非被压缩）。它是可以用任何方法制备的最纯净的材料之一，因为在这些温度下，杂质在获得液态所需的过程中被简单地冻结掉。最终he达到了一种高度有序的状态：超流动性，这与大多数超导体及其姊妹同位素he不同。超流体原子的磁性意味着原子成对在一起并进行轨道运动，表现出不同的相位。通过将3He限制在精确表征的几何形状中，有效地改变了3He的维度，这些行为会受到影响。通过对这些系统进行精确的测量，这项研究将增加我们对限制在不太极端条件下的作用的理解。该计划还将通过将研究生嵌入（并允许他们接待来自）使用不同技术探测相同系统的对应实验室，为日益国际化的科学和技术环境做好准备。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，为研究生和本科生在国家科技基础设施领域的成功职业生涯提供教育和培训。此外，该研究项目还将通过在夏季参与一名科学教师的研究，对未来的科技劳动力产生积极影响。