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

这个由材料研究部颁发的材料世界网络奖支持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被限制在与相干长度相当的长度时，3He的降维如何导致新的p波序参数。与金属系统不同的是，3He具有球面费米面，但各向同性的正常液体会产生各向异性的配对态。3He在小几何空间中的限制有望改变这一行为。理论上预言，受限超流3He在超流破坏的过程中将表现出平移对称性的破缺。尺寸约束也可能促进竞争相的稳定性，这些相在整体中并不明显。康奈尔大学开发了一项技术，可以制造具有良好特征的表面的限制几何图形，这些表面可以被图案化以达到指定的粗糙度。粗糙度会通过其稳定性和对无序的响应来影响所产生的相吗？这是一个重要的特征，对这项工作与凝聚态物理的更广泛的相关性具有影响。为了引入周期性并测试受限~3He新出现相对周期性的稳健性，我们还计划设计一种模式。我们还将构建和使用高精度流动池来研究4He、3He掺杂的4He薄膜以及3He在纳米多孔介质中的超流流动。这些要求苛刻的实验需要开发新的技术，为研究生和本科生提供了一个具有挑战性的环境，让他们获得技能(创新、发起、设计和实施的能力)，并熟悉分析和展示工具，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伙伴项目相结合。研究生将有机会通过在英国度过一个学期和在康奈尔大学招待同行来与同行合作。该研究计划还将在整个获奖期内纳入一名本科生。非技术摘要氦(与所有其他元素不同)本质上是量子力学的，即使在绝对零度以下也不会凝固(除非压缩)。它是任何方法都可以制备的最纯的材料之一，因为在这样的温度下，杂质在获得液态所需的过程中会被冻结。最终，3He达到了一种高度有序的状态：超流，这与大多数超导体及其姊妹同位素4He的超流状态不同。超流原子的磁性意味着原子配对在一起，并经历呈现不同相的轨道运动。将3He限制在精确表征的几何形状内，有效地改变了3He的维度，从而影响了这些行为。通过对这些系统进行精确的测量，这项研究将增加我们对在不那么极端的条件下限制的作用的理解。该项目还将通过将研究生植入(并允许他们接待来自)使用不同技术来探测相同系统的对应实验室的学生，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要求苛刻的实验环境，为研究生和本科生在国家科技基础设施中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暑期邀请一名科学教师参与这项研究，对未来的科技劳动力产生积极影响。

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.