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

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，以研究当这种非常规配对的超流体被限制在与相干长度相当的长度时，如何减少3 He的维数导致新的p波序参数。与金属系统相比，3 He具有球形费米表面;但各向异性配对状态出现在各向同性正常液体中。3 He在小几何形状中的限制预计会改变这种行为。理论上预言，受限超流3 He在超流性破坏的过程中会出现平移对称性破缺。尺寸约束也可能促进在本体中不明显的竞争相的稳定性。康奈尔大学开发了一种制造具有良好特征的表面的限定几何形状的技术，该表面可以被图案化以实现指定的粗糙度。粗糙度将影响所产生的阶段，通过其稳定性和响应无序？这是一个重要的特征，对这项工作与凝聚态物理学的更广泛的相关性有影响。还计划进行图案化，以引入周期性并测试受限3 He对周期性的新兴阶段的稳健性。 我们还将构建和使用高精度流动池来检查4 He，3 He掺杂的4 He薄膜的流动，并最终在纳米多孔介质中的超流3 He。这些要求苛刻的实验，需要开发新技术，提供了一个具有挑战性的环境，研究生和本科生获得技能（创新，启动，设计和执行的能力），以及熟悉分析和显示工具，为他们在国家的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。研究生将有机会通过在英国度过一个学期并在康奈尔大学主持同行与同行合作。非技术摘要氦（与其他元素不同）具有固有的量子力学性质，即使在绝对零度下也不会凝固（除非被压缩）。它是可以通过任何方式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简单地冻结。最后，3 He达到一种高度有序的状态：超流性，这与大多数超导体及其姊妹同位素4 He所达到的状态不同。超流体原子的磁性意味着原子配对在一起，并进行轨道运动，表现出不同的相位。这些行为受到限制3 He精确表征的几何形状，有效地改变3 He的维度。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的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，为研究生提供日益国际化的科学和技术环境。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，为研究生和本科生提供教育和培训，使他们在国家的科学和技术基础设施中取得成功。此外，这项研究计划还将通过在夏季让科学教师参与这项研究，对未来的科学和技术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.