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

人们普遍认为，通过所谓的顺磁子介导的吸引相互作用，液体^3He经历了一个形成p波库珀对的超流体相变。这一机制很好地解释了ABM态在较高压力和温度下的稳定性。另一方面，在正常状态下，液体^3He的磁性不能很好地用顺磁子理论来描述，而用近局域模型来描述是比较满意的。此外，最近有报道称，在气凝胶中的超流体^3He中，当不施加磁场时，不出现ABM状态。这表明杂质散射可能会改变对相互作用。从这些方面，我们研究了(1)考虑自旋涨落的正常液体^3He的磁化率，(2)杂质对气凝胶中^3He液体中声音传播的影响，(3)超流体和超导体边界问题的公式及其在近接触正常超导体系迈斯纳抗磁性表面效应中的应用。在磁化率的研究中，我们已经证明了费米表面奇点导致了磁化率的对数温度依赖。在对气凝胶中^3He液体中的声音的研究中，我们发现气凝胶由于碰撞阻力效应而产生的运动起主导作用。我们期望本研究将有助于理解气凝胶对液体^3He的杂质效应以及液体^3He在气凝胶中的配对机理。表面问题在解释声音传播，特别是像^3He这样的各向异性超流体中是非常重要的，因为声音是由表面的换能器激发的。我们已经建立了准经典理论的边界条件，现在正试图扩展该理论，使其能够处理动力学问题。

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.