Theoretical Studies of Dilute Alkali Gases and Amorphous Materials

稀碱气体与非晶材料的理论研究

• 批准号: 0350842
• 负责人: Anthony Leggett
• 金额: $ 60.8万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0350842&HistoricalAwards=false
• 关键词: Theoretical; Studies; Dilute; Alkali; Gases

This grant addresses theoretical questions in two challenging problems in emerging areas in condensed matter physics: properties of dilute alkali Bose and Fermi gases and the "universal" properties of amorphous materials.In the first area, several questions are addressed: (a) the behavior of a recently discovered state in which not one, but two, orbital single-particle states are macroscopically occupied; (b) the conditions under which the degree of Bose-Einstein condensation (BEC) may be inferred from Ramsey-fringe type experiments; (c) the detailed dynamics of the process by which a Bose gas trapped in an optical lattice in a "Mott-insulator" state converts into a superfluid (phase-coherent) state when the optical barriers are lowered or removed; (d) the behavior of a dilute Bose gas in the limit that the s-wave scattering length tends to infinity; (e) in a dilute two-species Fermi alkali-gas system having attractive inter-species interactions, to possible limits on the transition temperature to the BCS state, and/or on the pairing amplitudes.The second major thrust is more speculative in nature; an attempt is being made to implement quantitatively a proposal made several years ago concerning the "universal" behavior of amorphous materials (glasses), namely that this behavior has nothing to do with the ubiquitous presence in these materials of "tunneling-two-level systems," which is required by the currently established model, but rather is a quite generic consequence of the presence at short length scales of any kind of excitations that are not harmonic and that can be coupled by the elastic medium.In addition to these major two projects, work is ongoing on quenching in very degenerate Fermi systems and on cuprate superconductivity.The proposed projects are at the intellectual core of modern condensed matter physics and success will be of fundamental consequence. Likewise, successful completion of this research will affect many other fields of study. Students will be trained and the principal investigator is also writing a textbook on quantum liquids for beginning graduate students.%%%This grant addresses theoretical questions in two challenging problems in emerging areas in condensed matter physics - that branch of physics that deals with matter in its solid or liquid phases. The first area is theoretical studies of the properties of dilute, ultra-cold gases that condense into a unique quantum phase. Discovery of this unique phase, predicted many years ago, has earned recent Nobel Prizes. Much research has yet to be done. The second research area is the strange and "universal" behavior of amorphous materials (glasses). At very low temperatures diverse materials exhibit common properties indicating a common mechanism. A possible model for these common properties will be explored.The proposed projects are at the intellectual core of modern condensed matter physics and success will be of fundamental consequence. Likewise, successful completion of this research will affect many other fields of study. Students will be trained and the principal investigator is also writing a textbook on quantum liquids for beginning graduate students.***

该基金主要用于解决凝聚态物理学新兴领域中两个具有挑战性的理论问题：稀碱玻色和费米气体的性质以及非晶材料的“普适”性质。在第一个领域中，主要解决以下几个问题：（a）最近发现的一种状态的行为，在这种状态中，宏观上不是一个而是两个轨道单粒子态被占据;（B）从Ramsey条纹型实验中推断玻色-爱因斯坦凝聚度（BEC）的条件;（c）玻色气体在“莫特绝缘体”状态下被困在光学晶格中转化为超流体的过程的详细动力学（d）在s波散射长度趋于无穷大的极限下，稀玻色气体的行为;（e）在具有吸引的物种间相互作用的稀的两物种费米碱气体系统中，到BCS状态的转变温度的可能限制，和/或对振幅的影响。第二个主要推力本质上更具投机性;正在尝试定量地实施几年前提出的关于无定形材料（玻璃）的“普遍”行为的建议，即这种行为与这些材料中普遍存在的“隧穿两能级系统”无关，这是当前建立的模型所要求的，而是在短长度尺度上存在任何类型的非谐波激励并且可以通过弹性介质耦合的激励的相当一般的结果。除了这两个主要项目之外，目前正在进行的工作是在非常简并的费米系统中的淬火和铜氧化物超导性。2所提出的项目是现代凝聚态物理学的知识核心，成功将具有根本性的影响。 同样，这项研究的成功完成将影响许多其他研究领域。 学生将接受培训，首席研究员也在为刚开始的研究生编写量子液体教科书。该补助金解决了凝聚态物理学新兴领域中两个具有挑战性的问题的理论问题-物理学的分支涉及固体或液体相的物质。 第一个领域是理论研究的性质稀释，超冷气体冷凝成一个独特的量子相。 多年前预测的这一独特阶段的发现赢得了最近的诺贝尔奖。 许多研究工作尚待完成。 第二个研究领域是非晶材料（玻璃）的奇怪和“普遍”行为。 在非常低的温度下，不同的材料表现出共同的性质，表明共同的机制。 这些共同性质的一个可能的模型将被探索。拟议的项目是在现代凝聚态物理学的知识核心和成功将是根本性的后果。 同样，这项研究的成功完成将影响许多其他研究领域。 学生将接受培训，首席研究员也在为刚开始的研究生编写量子液体教科书。