Theory of Magnetism and Super-fluid Transition of Liquid He-3

人们普遍认为，液态^3 He在所谓的顺磁介导吸引相互作用的帮助下经历了超流相变，形成p波库珀对。这一机制很好地解释了ABM状态在较高压力和温度下的稳定性。另一方面，在正常状态下，液态^3He的磁性不能用顺磁子理论很好地描述，而可以用近局域模型来描述。此外，最近有报道称，在气凝胶中的超流^3 He中，当没有施加磁场时，ABM态不会出现。从这些方面出发，我们研究了（1）考虑自旋涨落的正常液态^3He的磁化率，（2）气凝胶中液态^3He中杂质对声传播的影响，（3）超流体和超导体边界问题的形式化及其在近场Meissner抗磁性表面效应中的应用接触正常的超导系统。在磁化率的研究中，我们已经表明，费米面奇异性引起的对数温度依赖的磁化率。在气凝胶中液态^3He的声研究中，我们发现气凝胶由于碰撞拖曳效应而产生的运动起着主导作用。我们希望这一研究将有助于理解气凝胶对液态^3He的杂质效应以及气凝胶中液态^3He的配对机制。表面问题在解释声音传播时非常重要，特别是在各向异性超流体（如^3He）中，因为声音是由表面的换能器激发的。我们已经制定了准经典理论的边界条件，现在试图扩展的理论，可以处理的动力学问题。

It is widely accepted that the liquid ^3He undergoes a superfluid phase transition forming p-wave Cooper pairs by aid of so-called paramagnon mediated attractive interaction. This mechanism explains well the stability of the ABM state at higher pressures and temperatures. On the other hand, in the normal state, magnetic properties of liquid ^3He is not well described by the paramagnon theory but rather satisfactory by nearly localized model. Moreover, it is recently reported that in the superfluid ^3He in aerogel, the ABM state does not appear when no magnetic field is applied. It implies that the pairing interaction may change due to the impurity scattering.From these aspects, we have studied (1)the susceptibility of normal liquid ^3He taking into account the spin fluctuation, (2)impurity effects on sound propagation in liquid ^3He in aerogel, (3) Formulation of boundary problem for superfluids and superconductors and its application to surface effect on Meissner diamagnetism of proximity-contact normal superconducting systems. In the study of the susceptibility, we have shown that the Fermi surface singularity gives rise to logarithmic temperature dependence of the susceptibility. In the study of sound in liquid ^3He in aerogel, we found that the motion of aerogel due to the collision drag effect plays a dominant role. We expect this study will contribute to the understanding of impurity effect by aerogel on liquid ^3He and also to the pairing mechanism of liquid ^3He in aerogel. The surface problem is very important in the interpretation of sound propagation, in particular anisotropic superfluid such as ^3He, because the sound is excited by transducers at the surface. We have formulated boundary condition for the quasi-classical theory and now trying to extend the theory such that can handle the dynamical problems.