Zero and Finite Temperature Critical Phenomena in Quantum Systems

该项目探索低温下物质的性质。 利用He-4的公认性质， 低温，以阐明一些问题，在冷凝 马特物理学 一个分项目涉及以下方面的影响： 受控缺陷对纯系统临界现象的影响。 的 向液体中引入低密度结构杂质 氦能使临界现象发生显著变化。 了解这个问题将增强我们对 缺陷的作用为更广泛的相变。 一 第二个方面是He-4膜中玻色子局域化的研究 吸附在异质衬底上。 物理学研究 一个玻色子系统，比如一个随机势中的氦膜， 一种异质基质，提供了一个有趣的补充， 金属-绝缘体转变和超导体的研究- 脏超导体中绝缘体转变 第三个主题将 是研究超流氦通过一个 多孔介质 这是一个玻色子类似物， 涡流液体和通量流状态的重要问题， 高温超导体 %%% 这个项目探索了物质在极低温度下的性质 温度低于零下450华氏度。 项目 研究的是一种超流体，氦，它表现出的行为， 类比，可以与其他材料中的现象相关， 特别是高Tc超导体。 此外，研究 处理相变并提供基本信息 与固-液熔融（和其他转化）有关， 存在于所有材料中。

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.