SGER: Superfluid State of Solid Helium Four

SGER：固态氦四的超流态

• 批准号: 0456862
• 负责人: Haruo Kojima
• 金额: --
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-15 至 2007-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0456862&HistoricalAwards=false
• 关键词: SGER; Superfluid; State; Solid; Helium

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.

最近的扭转振荡器实验表明，固体HE-4以下230 MK的超流量的第一个可能的证据。 现在，为超流体提供独立且独特的实验验证至关重要。 在这个SGER项目中，建议在Solid HE-4中搜索第四次声音的传播。 仅当材料变成超流体时，就会发生第四次声音传播，并且观察到它构成了无误的超流体证明。 提议使用超导膜重仪进行第一次在固体HE-4中进行此类搜索。当固体氦转化为超氟时，预计会在特定热量中具有相关的特征。 与Chan教授（宾夕法尼亚州立大学）合作，Rutgers University的固体HE-4的特定热量也将降至5 MK。 固体HE-4的超流体应影响其机械性能，例如其对外部施加应力的反应。 还建议搜索超压心性对液体固体界面上应力驱动不稳定性现象的影响。 这三个提出的实验都是风险的，因为超固体相的行为在很大程度上尚不清楚。结果的影响将是巨大的：它将在实验和理论中开辟一个新的研究领域，以研究低温下“超摩托车”背后的基本物理机制。拟议的研究将在低温物理学基础研究的高级原理和技术中揭示和培训本科生，毕业生和研究生。拟议的基础研究中的经验将为年轻科学家提供智力基础，以准备在整个学术界，行业和社会的未来职业中做准备。%%;固体可以像没有粘度一样流动吗？ 根据最近进行的实验，该答案是肯定的，该实验是在非常低的温度下测量固体氦四的旋转惯性，仅比绝对零温度的十分之一度。 现在，为固体氦的超流体提供独立且独特的实验验证至关重要。通过一系列研究，该SGER项目试图证明或反驳“超固体氦”的存在。 Supersolid（或其他）证据证明的影响将是巨大的：它将在实验和理论中开辟一个新的研究领域，以研究低温下“超杀手”背后的基本物理机制。当我们理解这种新型现象时，应成为可能的材料特性（如摩擦，粘附和流动）的改进和控制。 因此，这些研究对基本科学以及最终的技术进步产生了广泛而重要的影响。 该项目将尝试通过寻找第四次声音传播来提供独立的固体氦气超流体证明，除非材料是超流体，否则不会发生这种情况。 第四次声音是声波，其中只有超流体分数移动，使其余的固体静止。 观察第四次声音传播将提供明显的超流体证明。 该项目的另一部分是测量固体氦气的热容量，四到0.005 K，以寻找超流体过渡的热力学特征。 拟议的研究将在低温物理学基础研究的高级原理和技术中揭示和培训本科生，毕业生和研究生。 拟议的基础研究的经验将为年轻科学家奠定知识基础，以准备在整个学术界，工业和社会的未来职业。