SGER: Superfluid State of Solid Helium Four

最近的扭振实验首次证明了固体He-4在230 mK以下可能存在超流动性。现在至关重要的是提供一个独立和独特的超流动性实验验证。在这个SGER项目中，我们提出在固体He-4中寻找第四声的传播。第四，只有当物质变成超流体时，声音传播才会发生，并且对它的观察构成了超流体的确凿证据。建议在固体He-4中使用超导薄膜测热仪进行第一次这样的搜索。当固体氦转变为超流体时，预计会有一个相关的比热特征。与陈教授的团队（宾夕法尼亚州立大学）合作，罗格斯大学也将测量固体He-4的比热降至5 mK。固体He-4中的超流动性会影响其力学性能，如对外应力的响应。还提出了寻找超固体性对液固界面应力驱动不稳定现象的影响。这三个实验都是有风险的，因为超固相的行为在很大程度上是未知的。结果的影响将是巨大的：它将在实验和理论方面开辟一个新的研究领域，以研究低温下“超固体”背后的基本物理机制。本课题旨在培养本科生、研究生和研究生了解低温物理基础研究的先进原理和技术。在拟议的基础研究中的经验将为年轻科学家奠定智力基础，为他们未来在学术界、工业界和整个社会的职业生涯做准备。有没有可能一种固体可以像没有粘度一样流动？根据最近进行的一项实验，答案是肯定的，该实验是在非常低的温度下测量固体氦4的旋转惯量，仅比绝对零度高零点几度。现在至关重要的是提供一个独立的和独特的实验验证固体氦的超流动性。通过一系列的研究，SGER项目试图证明或反驳“超固体氦”的存在。超固体（或其他）确证的影响将是巨大的：它将在实验和理论上开辟一个新的研究领域，以研究低温下“超固体”背后的基本物理机制。当我们理解这种新现象时，改进和控制材料的性能，如摩擦、附着力和流动，应该成为可能。因此，这些研究对基础科学以及最终的技术进步具有潜在的广泛而重要的影响。该项目将试图通过寻找第四次声音传播来给出固体氦4超流动性的独立证明，除非材料是超流体，否则不会发生这种情况。第四种声音是声波，其中只有超流体部分移动，其余固体静止不动。对第四种声音传播的观察将提供超流体的确凿证据。该项目的另一部分是测量固体氦4的热容量，直到0.005 K，以寻找超流体转变的热力学特征。本课题旨在培养本科生、研究生和研究生了解低温物理基础研究的先进原理和技术。在拟议的基础研究中的经验将为年轻科学家奠定智力基础，为他们未来在学术界、工业界和社会上的职业生涯做准备。

Recent torsion oscillator experiments showed the first probable evidence of superfluidity of solid He-4 below 230 mK. It is now crucial to provide an independent and distinct experimental verification of the superfluidity. In this SGER project, it is proposed to search for propagation of fourth sound in solid He-4. Fourth sound propagation occurs only if the material becomes superfluid and the observation of it constitutes an unmistakable proof of superfluidity. It is proposed to conduct the first such search in solid He-4 using a superconducting film bolometer. When solid helium transforms into a superfluid, an associated signature in specific heat is expected. In collaboration with Prof. Chan's group (Pennsylvania State University), the specific heat of solid He-4 will also be measured down to 5 mK at Rutgers University. The superfluidity in solid He-4 should affect its mechanical properties such as its response to externally applied stress. It is also proposed to search for the influence of supersolidity on the phenomenon of stress-driven instability at the liquid solid interface. All three proposed experiments are risky since the behavior of the supersolid phase is largely unknown. The impact of the results will be enormous: it will open up a new field of research in both experiment and theory to study the fundamental physical mechanism behind the "supersolidity" at low temperatures. The proposed research will expose and train undergraduates, graduates and post-graduates in the advanced principles and technologies in fundamental research in low temperature physics. The experience in the proposed basic research will lay the intellectual foundation for the young scientists in preparation for their future careers in academia, industries and society at large.%%%Is it possible that a solid can flow as if it has no viscosity? The answer is affirmative according to the recent experiment carried out to measure the rotational inertia of solid helium four at very low temperatures, just a few tenths of a degree above the absolute zero temperature. It is now crucial to provide an independent and distinct experimental verification of the superfluidity of solid helium. Through a series of studies, this SGER project attempts to prove or disprove the existence of "supersolid helium." The impact of corroborative proof of supersolid (or otherwise) will be enormous: it will open up a new field of research in both experiment and theory to study the fundamental physical mechanism behind the "supersolidity" at low temperatures. When we understand this novel phenomenon, improvements and control of materials properties such as friction, adhesion, and flow, should become possible. Thus, these studies have potentially broad and important impacts on fundamental science as well as eventual technological advancement. The project will attempt to give an independent proof of superfluidity of solid helium four by searching for the fourth sound propagation, which would not occur unless the material is a superfluid. The fourth sound is the acoustic wave in which only the superfluid fraction moves leaving the rest of solid at rest. Observation of the fourth sound propagation will provide an unmistakable proof of superfluidity. Another part of the project is to measure the heat capacity of solid helium four down to 0.005 K in search of thermodynamic signature of the superfluid transition. The proposed research will expose and train undergraduates, graduates and post-graduates in the advanced principles and technologies in fundamental research in low temperature physics. The experience in the proposed basic research will lay the intellectual foundation for the young scientists in preparation their future careers in academia, industries and society at large.