Spin Dynamics and Strong Coupling in Helium Three

摘要本项目采用核磁共振技术研究3He的超流相。该研究包括对氦在A相和B相的磁矩进行高精度测量，以及确定偶极-偶极耦合能对超流体自由能的贡献。仅在气凝胶的约束几何中发现的新型4He / 4He稀混合物也将被研究，以表征这些体系中的混相间隙，并研究这些新材料中的扩散和弛豫现象。分子有机固体的核磁共振研究将集中在这些准一维固体中金属态起源的基本问题上。实验将涉及超低温和高磁场。非技术摘要：本课题采用低温核磁共振技术研究3He的超流相行为。这些系统在非常低的温度下显示出不同寻常的量子效应。在这些超流体系统中获得的信息具有重要的意义，并且与其他费米液体系统（如高温超导体）的联系也具有重要的意义。该项目的另一部分涉及研究在透明、超高表面积气凝胶材料中稀释4He的3He薄膜。这项研究将提供有关这些材料表面相互作用的信息，以及有关相行为的基本信息，如氦的两种同位素的混溶性。最后，该项目包括高纯度分子有机固体的核磁共振研究，这些固体具有金属特征，电导率具有准一维各向异性。这里的重点是从绝缘状态到导电状态相变的基本方面。＊＊＊

9314025 Halperin Technical Abstract: The project employs nuclear magnetic resonance to investigate the superfluid phases of 3He. The research involves high precision measurements of the magnetic moment of the helium in the A and B phases, as well as determination of the contribution of the dipole-dipole coupling energies to the superfluid free energy. The novel dilute mixtures of 4He in 4He, found only in constrained geometries of aerogels will also be investigated to characterize the miscibility gap in these systems and to investigate diffusion and relaxation phenomena in these new materials. The NMR studies of molecular organic solids will focus on fundamental questions concerning the origin of the metallic state in these quasi-one- dimensional solids. The experiments will involve ultralow temperatures and high magnetic fields. Non-technical abstract: The research project employs low temperature nuclear magnetic resonance to study the behavior of superfluid phases of 3He. These systems display unusual quantum effects at very low temperatures. The information obtained in these superfluid systems is of fundamental interest, and also is of interest in connection with other Fermi liquid systems, such as the high temperature superconductors. Another part of the project involves studies of thin films of dilute 4He in 3He constrained in the diaphanous, ultrahigh surface area aerogel materials. The research will provide information about surface interactions in these materials, as well as providing fundamental information about phase behavior such as miscibility of the two isotopes of helium. Finally, the project includes NMR studies of high purity molecular organic solids which display metallic character with the conductivity having a quasi-one-dimensional anisotropy. Here the focus is on fundamental aspects of the phase transition from an insulating to conducting state. ***