NMR Studies of the Mechanism of Superconductivity and Spin Fluctuations in High Tc and Related Layered Oxides

掺杂铜氧化物的高温超导机理仍存在很大争议。最根本的困难在于，强载流子-载流子相关效应不允许我们基于传统智慧来描述Tc以上的正常金属态。此外，未掺杂的母体反铁磁绝缘体的磁性和统计性质很难理解。最近，麻省理工学院材料科学与工程中心设计并开发了一种新的核磁共振光谱仪，该光谱仪非常适合研究载流子-载流子相关效应、金属-绝缘体跃迁、准二维量子自旋系统的磁性和统计特性、超导序参量的对称性以及相关现象。在本项目中，将使用光谱仪研究多种高Tc氧化铜超导体及相关材料，特别强调高温下的核磁共振实验。核磁共振技术是一种理想的微观的、无损的探测固体物理和化学性质的方法。最近，麻省理工学院材料科学与工程中心开发了一种新的核磁共振光谱仪，该光谱仪允许人们进行独特的实验来研究高温超导体和相关材料。最值得注意的是，在高温下进行的困难实验可以以常规方式进行。本项目将利用核磁共振谱仪了解氧化铜超导体的高温超导机理及相关现象。* * *

9623858 Imai The mechanism of high temperature superconductivity in doped copper oxides is still highly controversial. The fundamental difficulty lies in the fact that strong carrier-carrier correlation effects do not allow us to describe the normal metallic state above Tc based on the conventional wisdom. Moreover, the magnetism and statistical properties of the undoped parent antiferro- magnetic insulators are hard to understand. Recently, a new NMR (Nuclear Magnetic Resonance) spectrometer has been designed and developed at the Center for Materials Science and Engineering at M.I.T. The spectrometer is ideally suited to investigate carrier- carrier correlation effects, metal-insulator transitions, magnetic and statistical properties of quasi 2d quantum spin systems, the symmetry of the superconducting order parameter, and related phenomena. In the proposed project, a variety of high Tc copper oxide superconductors and related materials will be studied using the spectrometer with particular emphasis on NMR experiments at elevated temperatures. %%% The nuclear magnetic resonance technique is an ideal microscopic, nondestructive probe into the physical and chemical properties of solids. Recently, a new NMR spectrometer has been developed at the Center for Materials Science and Engineering at M.I.T. The spectrometer allows one to conduct unique experiments to investigate high temperature superconductors and related materials. Most notably, difficult experiments at elevated temperatures can be conducted in a routine manner. In the proposed project, the NMR spectrometer will be utilized to understand the mechanism of high temperature superconductivity and related phenomena in copper oxide superconductors. ***