Ultrasound in Superfluid Helium at Microkelvin Temperatures

微开尔文温度下超流氦中的超声波

• 批准号: 9022733
• 负责人: Mark Meisel
• 金额: --
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-02-15 至 1992-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9022733&HistoricalAwards=false
• 关键词: Ultrasound; Superfluid; Helium; Microkelvin; Temperatures

The energy gap in superfluid 3He-B is to be measured over a wide range of pressure and at low T/Tc. Ultrasound will be used to measure the pair-breaking edge, 2 (P,T), in the T-- O limit, for the first systematic test of the quasiclassical weak-coupling + WCP theory of Serene and Raianer. In addition, the proposed work will provide a stringent self-consistency check on the WCP model and the heat-capacity and phase-diagram results of Greywall. Performing the experiments in the microkelvin temperature regime will make the results less sensitive to problems in theomometry compaired with work at higher temperatures where very high accuracy is required. Furthermore, the very-low-temperature work will permit a study of the possible defects in the theoretical picture, as suggested by experiments at high temperature and high pressure. Finally, the reearch requires the development of broadband acoustic techniques and their extension to miocrokelvin temperatures. This research examaines the role of quantum mechanics in determining the fundamental properties of matter through high- frequency acoustic probing of liquid 3He at temperatures less than lnK above absolute zero.

超流体 3He-B 中的能隙需要在宽压力范围和低 T/Tc 下测量。 超声波将用于测量 T--O 极限中的配对断裂边缘 2 (P,T)，这是对 Serene 和 Raianer 的准经典弱耦合 + WCP 理论的首次系统测试。 此外，拟议的工作将对 WCP 模型以及 Greywall 的热容和相图结果进行严格的自我一致性检查。 与需要非常高精度的较高温度下的工作相比，在微开尔文温度范围内进行实验将使结果对测温问题不太敏感。 此外，正如高温高压实验所表明的那样，极低温工作将允许研究理论图中可能存在的缺陷。 最后，研究需要开发宽带声学技术并将其扩展到微开尔文温度。 这项研究通过在绝对零以上 lnK 以下的温度下对液体 3He 进行高频声波探测，检验了量子力学在确定物质基本性质方面的作用。