Ultrasound in Superfluid Helium at Microkelvin Temperatures

超流体3He-B的能隙是在较宽的压力范围和较低的温度/温度下测量的。超声波将用于测量T—O极限的对破边2 (P，T)，这是对Serene和Raianer的准经典弱耦合+ WCP理论的第一次系统测试。此外，所提出的工作将对WCP模型和Greywall的热容和相图结果提供严格的自一致性检查。在微开尔文温度下进行实验，与在需要很高精度的较高温度下工作相比，将使结果对几何问题不那么敏感。此外，极低温的工作将允许研究理论图景中可能存在的缺陷，正如在高温高压下进行的实验所表明的那样。最后，研究需要宽带声学技术的发展，并将其扩展到微开尔文温度。本研究考察了量子力学在确定物质基本性质中的作用，通过在绝对零度以上低于lnK的温度下对液体3He进行高频声波探测。

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.