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

我们用气凝胶研究了超流体和正常流体^3He边界处的邻近效应。气凝胶的孔隙率为97.5%，这对应于2.5%的杂质。我们将气凝胶注入半个细胞，并在中心形成边界。我们通过将^3He或^4He气体分别吸附在气凝胶的二氧化硅链上来制备磁性或非磁性杂质。用NMR方法测量了核自旋结构，发现2.5%杂质中^3He的超流转变温度比低杂质中的低。在2.1MPa以上的压力下，我们发现了两种超流相，并通过脉冲核磁共振方法进行了澄清：在较高温度下的相是类ABM（A-like），另一种是类BW（B-like）。这些现象与窄空间中的^3He有很大的不同，并且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转变温度高于磁性杂质。这些结果表明，库珀对的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相的共存状态。我们还观察到在边界处的共存状态，发现它在边界处的比例与杂质中的相同。该结果表明邻近效应不影响共存状态。另一方面，我们观察到一个特殊的自旋结构之间的边界处的超流状态的散装和正常状态的杂质。这些应该是由边界的邻近效应造成的。

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.