Ultrasound in Superfluid Helium at Microkelvin Temperatures

超流3He-B的能隙是在很宽的压力范围内和低T/T_c下测量的。为了首次系统地检验Serene和Raianer的准经典弱耦合+WCP理论，将利用超声测量T-O极限中的对断裂边2(P，T)。此外，拟议的工作将对WCP模型以及灰墙的热容和相图结果进行严格的自洽检查。在微开尔文温度范围内进行实验将使结果对理论测量中的问题不那么敏感，与在更高温度下工作相比，那里需要非常高的精度。此外，极低温度的工作将允许研究高温高压下的实验所建议的理论图像中可能的缺陷。最后，这项研究需要发展宽带声学技术并将其扩展到Miocrokelvin温度。这项研究通过在绝对零度以上温度低于lnk的情况下对液体3He进行高频声波探测，研究了量子力学在确定物质基本性质方面的作用。

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.