Search for Bose-Einstein Condensation in Solid 'He'

这是一个低温物理项目，涉及最近在含有少量He-3的He-4晶体中发现的一些有趣的声音传播异常。异常涉及声速和1 K附近的声衰减，并与He-3杂质的浓度有关。人们提出了一个猜想，认为这些异常现象可以用玻色-爱因斯坦凝聚来解释。这个项目的目的是进行精确的测量，以确定这些异常是否为弹道或第二声模式传播的新激励家族提供证据，以及观察到的相变是否真的是这些激励的玻色-爱因斯坦凝聚。这个项目为培养当代物理学前沿领域的研究生提供了一个机会。对低温物理学的研究导致发现了一种叫做玻色-爱因斯坦基本粒子凝聚的现象，最近发现了超冷原子，这种现象早在20世纪20年代就被预测到了。最近，人们发现，在固体氦-4（这种元素最常见的品种）中，当固体中含有少量的轻同位素氦-3作为杂质时，声音的传播和衰减会发生一种特殊的、迄今尚未被理解的行为。对于这种反常行为没有公认的解释，并且认为观察到的现象是由于玻色-爱因斯坦凝聚的建议受到怀疑。拟议的研究旨在提供更准确和详细的数据，以便对异常进行明确的解释。这个问题的解决对凝聚态物理学具有根本的重要性。这个项目为培养当代物理学前沿领域的研究生提供了一个机会。＊＊＊

9802046 Goodkind This is a low temperature physics project which deals with a recent discovery of some interesting anomalies in the propagation of sound in He-4 crystals containing small amounts of He-3. The anomalies involve the sound velocity and the acoustic attenuation at a temperature near 1 K and depend on the concentration of the He-3 impurity. A conjecture has been made that these anomalies can be explained on the basis of a Bose-Einstein condensation. The purpose of this project is to perform refined measurements to determine whether the anomalies give evidence for a new family of excitations which travel ballistically or in a second sound mode, and whether the observed phase transition is a truly Bose- Einstein condensation of these excitations. This project offers an opportunity for the training of graduate students in a forefront area of contemporary physics. %%% Research in low temperature physics has resulted in the discovery of a phenomenon called the Bose-Einstein condensation of elementary particles and, more recently, ultra cold atoms, an effect which was predicted in the 1920's. Still more recently, a discovery was made that in solid helium-4 (the most common variety of this element) a peculiar and as yet not understood behavior of the propagation of sound and its attenuation takes place when the solid contains a small amount of the light isotope helium-3 as an impurity. There is no accepted explanation available for this anomalous behavior and a suggestion that the observed phenomenon is due to a Bose-Einstein condensation is met with skepticism. The proposed research is designed to provide more accurate and detailed data which will allow a definitive interpretation of the anomaly. The resolution of this problem is of fundamental importance to the physics of condensed matter. This project offers an opportunity for the trainin g of graduate students in a forefront area of contemporary physics. ***