Zero and Finite Temperature Critical Phenomena in Quantum Systems

量子系统中的零温度和有限温度临界现象

• 批准号: 9303855
• 负责人: John Reppy
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-07-01 至 1997-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9303855&HistoricalAwards=false
• 关键词: Zero; Finite; Temperature; Critical; Phenomena

This project explores the properties of matter at low temperatures. Advantage is taken of the well-established properties of He-4 at low temperatures to illuminate a number of problems in condensed maatter physics. One sub-project addresses the influence of controlled defects on the critical phenomena of a pure system. The introduction of a low density structural impurity into liquid helium can produce a striking alteration in the critical pehnomena. An understanding of this problem will enhance our understanding of the role of defects for a wider range of phase transitions. A second area is the study of boson localization in He-4 films adsorbed on a heterogeneous substrate. The study of the physics of a boson system, such a a helium film in the random potential of aheterogeneous substrate, offers an interesting complement to studies of the metal-insulator transition and the superconductor- insulator transition in dirty superconductors. A third topic will be the study of a dissipative flow of superfluid helium through a porous medium. This is a boson analog to the technologically important problem of the vortex liquid and flux-flow regimes of high Tc superconductors. %%% This project explores the properties of matter at very low temperatures--below minus 450 degrees Fahrenheit. The project deals with a superfluid, helium, which exhibits behavior which, by analogy, can be related to phenomena in other materials, particularly high Tc superconductors. In addition, the research deals with phase transitions and provides fundamental information bearing on solid-liquid melting (and other transformations) that occurs in all materials.

这个项目探索物质在低温下的性质。利用He-4在低温下的良好性质，阐明了凝聚态数学物理中的一些问题。一个子项目解决了受控缺陷对纯系统的临界现象的影响。在液氦中引入低密度结构杂质可以引起临界现象的显著变化。对这一问题的理解将增强我们对缺陷在更大范围的相变中的作用的理解。第二个领域是研究吸附在非均质衬底上的He-4薄膜中的玻色子局域化。玻色子系统的物理研究是对脏超导体中金属-绝缘体相变和超导体-绝缘体相变的有趣补充。第三个主题是研究超流氦在多孔介质中的耗散流动。这是一个与高T_c超导体的涡旋液体和磁通流态的重要技术问题类似的玻色子。这个项目探索物质在极低温度下的性质--低于零下450华氏度。该项目涉及一种超流体氦，通过类比，它的行为可以与其他材料中的现象有关，特别是高T_c超导体。此外，这项研究还涉及相变，并提供了与所有材料中发生的固-液熔化(和其他转变)有关的基本信息。