Liquid and Solid Helium at Very Low Temperatures

对液氦3和液氦4在0.1K以下的温度下进行了四个实验：1)测量了溶解度和扩散系数，以验证费米液体理论的一些最新预测。2)测量Kapitza热导和横向自旋波在氦3的超流A和B相界面上的传输，以及3)涉及氦3/氦4混合物的相关实验，这两个实验旨在确定氦3准粒子在界面上的传输几率。4)通过测量质子在液氦自由表面的反射几率来检验最新的理论。4.氦(和氢)的液态只能在接近绝对零度的极低温度下产生，提供了一个“量子流体”的例子，其中自然向我们展示了一个在“整体”(或“宏观”)尺度上运行的量子力学的例子。这种流体证明了非常不寻常的性质，并为研究物质的基本性质提供了肥沃的土壤。目前的实验旨在深入研究其中的一些性质，从而加深我们对物理世界这个奇怪领域的理解。

Four experiments on liquid helium 3 and helium 4 at temperatures below 0.1K are proposed: 1) Solubility and diffusion- coefficient measurements to test some recent predictions of Fermi Liquid theory. 2) Measurement of the Kapitza thermal conductance and of the transmission of transverse spin waves across the interface between superfluid A and B phases of helium 3, and 3) a related experiment involving helium 3/helium 4 mixtures, these two experiments being designed to determine the transmission probabilities of helium 3 quasiparticles across the interfaces. 4) A test of recent theory by measuring the reflection probability of rotons at the free surface of liquid helium 4. The liquid state of helium (and hydrogen), which can only be produced at extremely low temperatures, close to absolute zero, furnishes an example of a "quantum fluid" where Nature shows us an example of quantum mechanics operating on a "bulk" (or "macroscopic") scale. Such a fluid evidences very unusual properties and offers a fertile ground for research into the fundamental properties of matter. The present experiments are designed to examine some of those properties in depth and thus deepen our understanding of this strange realm of the physical world.