Proximity Effect at the Boundary between Super and Normal Fluid Helium 3

本文用气凝胶研究了超常规流体^3He边界处的邻近效应。气凝胶孔隙率为97.5%，杂质含量为2.5%。我们将气凝胶注射到半个细胞中，并在中心形成一个边界。我们通过在气凝胶的硅链上分别吸附^3He或^4He气体来制备磁性或非磁性杂质。我们用核磁共振法测量了原子核的自旋结构。2.5%杂质中^3He的超流体转变温度低于低杂质中的超流体转变温度。在2.1 MPa以上的压力下，我们发现了两种类型的超流体相，并通过脉冲核磁共振方法进行了澄清：高温下的超流体相为ABM-like （A-like）和BW-like （B-like）。这些现象在狭窄的空间中与^3He有很大的不同，气凝胶的链被认为是^3He的杂质。在非磁性杂质中观察到的超流体转变温度高于磁性杂质。结果表明，铜偶的p波很容易被磁性杂质破坏。我们只在非磁性杂质中观察到^3He的类a相和类b相共存状态。我们还观察了边界处的共存态，发现其在边界处的比值与杂质中的比值相同。这一结果表明邻近效应不影响共存态。另一方面，我们观察到在本体的超流态和杂质的正常态之间的边界处有一种特殊的自旋结构。这些应该是由边界上的邻近效应引起的。

We have investigated the proximity effect at the boundary of super and normal fluid ^3He using an aerogel. The porosity of the aerogel was 97.5 %, which corresponds to 2.5 % impurity. We injected the aerogel into a half of a cell and formed a boundary at the center. We prepared magnetic or non-magnetic impurities by adsorbing ^3He or ^4He gas, respectively, on the silica strands of the aerogel. We measured the nuclear spin structures by the NMR method.The superfluid transition temperature of ^3He in the 2.5 % impurities is lower than those in lower impurities. We found two types of the superfluid phases at pressures above 2.1 MPa and clarified those by the pulsed NMR method : the phase at higher temperatures is the ABM-like (A-like) and the other the BW-like (B-like). Those phenomena are quite different from ^3He in narrow spaces, and the strands of the aerogels are considered impurities for ^3He.The superfluid transitions were observed at higher temperatures in non-magnetic impurities than in magnetic impurities. Those results indicate that the p-wave of Cooper pairs are easily destroyed by the magnetic impurities. We observed a coexistence state of the A-like and the B-like phase of ^3He only in the non-magnetic impurities. We also observed the coexistence state at the boundary and found that its ratio at the boundary is as same as in the impurities. This result suggests that the proximity effect does not affect the coexistence state. On the other hand we observed a peculiar spin structure at the boundary between the superfluid state in the bulk and the normal state in the impurities. Those should be caused by the proximity effect at the boundary.