Applications of the Ordered Phases of Helium Three to Broader Questions in Physics

氦三有序相在更广泛的物理问题中的应用

• 批准号: 9971694
• 负责人: Douglas Osheroff
• 金额: $ 33万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9971694&HistoricalAwards=false
• 关键词: Applications; Ordered; Phases; Helium; Three

9971694OsheroffThis is a low temperature physics project dealing with less abundant isotope of helium, He-3. The low temperature ordered phases of solid and liquid He-3 exhibit complex yet remarkably well understood and easily measured physical properties which in many instances mimic the behavior seen less clearly in systems with much greater technological importance. For instance, one can easily observe antiferromagnetic domain walls in the U2D2 spin ordered phase of solid He-3 from shifts in the NMR spectra of the adjacent magnetic domains. This ability will be utilized in the present research program to study domain wall pinning and mobility in an antiferromagnet cleanly for the first time. This knowledge should be useful in understanding the stability of magnetic systems on a mesoscopic scale, and macroscopic tunneling phenomena generally. In another example, the p-wave 3He BCS superfluid ground state would be infinitely degenerate at Tc were it not for critical fluctuations, which are predicted to stabilize phases near Tc which are different from those seen at lower temperatures. This research program will probe the width of this region, and attempt to identify the ordered phases near Tc, thus providing a new test of our understanding of the theory of critical phenomena. The project educates primarily graduate students, although physics majors carry out senior honors projects in the lab as well. Students who pursue low temperature studies obtain a rigorous and very broad education in condensed matter physics and experimental techniques. %%%This low temperature physics project will utilize many of the unique properties of the low temperature phases of solid and liquid He-3 to study specific properties of these ordered phases whose physical origins are common to properties seen in other more technologically important materials, such as those used in magnetic memory devices. In one set of experiments, the nature and mobility of the boundaries between magnetically ordered domains with different orientations will be studied in a magnetically ordered phase of solid 3He using magnetic resonance techniques. This study will bear on the question of how a system can quantum mechanically tunnel through a barrier which is too high for it to go over. A second study will involve superfluid 3He, which exhibits ordered phases similar to those seen in conventional superconductors, but much more complex. The nature of the superfluidity just below the transition to the ordered state will be used in a novel test of the theory which appears to successfully describe all second order, or 'continuous' phase transitions. This will provide a unique test of the applicability and validity of this Nobel prize winning theory. The project educates primarily graduate students, although physics majors carry out senior honors projects in the lab as well. Students who pursue low temperature studies obtain a rigorous and very broad education in condensed matter physics and experimental techniques. ***

9971694Osheroff这是一个低温物理项目，研究氦丰度较低的同位素He-3。固体和液体He-3的低温有序相表现出复杂但非常容易理解和容易测量的物理性质，在许多情况下模仿了在具有更大技术重要性的系统中不太清楚的行为。例如，在固体He-3的U2D2自旋有序相中，人们可以很容易地从相邻磁畴的核磁共振谱中观察到反铁磁性磁畴壁。这一能力将在本研究计划中首次被用来干净地研究反铁磁体中的磁区壁钉扎和迁移率。这一知识对于理解介观尺度上磁系统的稳定性以及宏观隧穿现象应该是有用的。在另一个例子中，如果没有临界涨落，p波3He BCS超流基态将在Tc处无限简并，预计在Tc附近稳定相不同于在较低温度下看到的相。这个研究项目将探索这一区域的宽度，并试图确定T_c附近的有序相，从而为我们对临界现象理论的理解提供一个新的检验。该项目主要培养研究生，尽管物理专业的学生也要在实验室里完成高级荣誉项目。从事低温研究的学生在凝聚态物理和实验技术方面获得严格而广泛的教育。这个低温物理项目将利用固体和液体He-3低温相的许多独特性质来研究这些有序相的特定性质，这些有序相的物理起源与在其他更重要的技术材料中看到的性质相同，例如用于磁存储器件的那些。在一组实验中，将使用磁共振技术研究固体3He的磁有序相中不同取向的磁序域之间的边界的性质和迁移率。这项研究将涉及这样一个问题，即一个系统如何以量子力学的方式穿越一个太高而无法逾越的障碍。第二项研究将涉及超流3He，它的有序相类似于传统超导体中的相，但要复杂得多。在转变到有序状态下的超流性的性质将被用于对该理论的一种新颖的测试，该理论似乎成功地描述了所有的二级相变，或者说“连续”相变。这将为这一诺贝尔奖获得者理论的适用性和有效性提供一个独特的考验。该项目主要培养研究生，尽管物理专业的学生也要在实验室里完成高级荣誉项目。从事低温研究的学生在凝聚态物理和实验技术方面获得严格而广泛的教育。***