Orderings in Highly Quantal Light Element Systems

高量子轻元件系统的订单

• 批准号: 0601461
• 负责人: Neil Ashcroft
• 金额: $ 36万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0601461&HistoricalAwards=false
• 关键词: Orderings; Highly; Quantal; Light; Element

TECHNICAL SUMMARY:This award supports theoretical research and education focused mainly on the light elements, including hydrogen under conditions of high pressure and eventually high temperature. The PI aims to elucidate quantum orderings, both in hydrogen and in hydrogen alloyed with other light element systems. Of increasing prominence in these systems is the enduringly fundamental and pragmatic area of superconductivity, impelled by the recent and quite dramatic discovery of superconductivity occurring in compressed lithium with a transition temperature which is now the highest of any element. That this could be a possibility was already raised in research supported by the previous grant and companion predictions that the hitherto 'simple' elements would adopt structures of considerable complexity at similar conditions were also swiftly borne out by experiment. It is remarkable that many of the elements hitherto regarded as 'simple' are observed to take up structures at higher densities even exhibiting incommensurabilities. And it is surely also noteworthy that the light elements in the especial combination MgB2 have had such a significant impact on the field of superconductivity. A major theme of the research is spurred by striking recent advances in experimental high pressure physics. The PI aims to elucidate the physics of the superconducting state, and particularly the role of electronic fluctuation in multi-band and quasi-localized contexts. High temperature superconductivity has long been predicted to occur in metallic phases of hydrogen and now more recently in hydrogen dominant metallic alloys. Further development of the theory for this class of system seems in order, especially to explore the possibility of further orderings that might accompany sublattice melting. For pure hydrogen itself, co-existence of superfluidity and superconductivity has been predicted for liquid metallic (near) ground states, and extension of the theory now to the mixed symmetry system embodied by liquid metallic deuterium is an interesting avenue to pursue, again with an eye towards experimental realization. The vortex characteristics, resulting either from applied magnetic fields or from rotation, may be unusual. In electronic terms all of these systems are highly inhomogeneous, as guaranteed by the cusp theorem, and it is also proposed to further develop weighted density and related approaches to the density functional viewpoint of the associated electronic structures, both for energetics and for effective interactions. NON-TECHNICAL SUMMARY:This award supports theoretical research and education in condensed matter physics focused mainly on the light elements, including hydrogen under extermes of pressure and temperature. Under a previous award the PI has predicted that novel superconducting and superfluid states in these systems will arise when exposed to a magnetic field or when they are rotated. A key feature of this work is the prediction of key signatures that could be observed in experiments. While hydrogen under enormous pressure exists in various places in our solar system and elsewhere in the universe, recent advances in experimental high pressure techniques suggest that the discovery of exciting new phases of matter with potential technological applications is coming within grasp. Among the possibilities are superconducting states that occur at high temperature in the light elements under high pressure. The PI will continue and extend his theoretical work to predict and explore new states of matter that may emerge in the seemingly simplist elements. Hydrogen and hydrogen dominant metallic alloys under high pressure will be a particular focus of the work. This research may have impact on other disciplines and will provide a training ground for future scientists.

技术概述：该奖项主要支持轻元素的理论研究和教育，包括高压和高温条件下的氢。PI的目标是阐明氢和氢合金与其他轻元素系统的量子顺序。在这些系统中，日益突出的是超导性的持久基础和实用领域，这是由最近在压缩锂中出现的超导性的相当戏剧性的发现所推动的，其转变温度目前是所有元素中最高的。这种可能性在之前的研究中已经被提出，并且伴随的预测是，迄今为止“简单”的元素在类似的条件下会采用相当复杂的结构，这也很快被实验证实了。值得注意的是，许多迄今为止被认为是“简单”的元素被观察到以更高的密度占据结构，甚至表现出不可通约性。同样值得注意的是，MgB2特殊组合中的轻元素对超导领域产生了如此重大的影响。这项研究的一个主要主题是由高压物理实验的最新进展所激发的。该项目旨在阐明超导态的物理性质，特别是电子涨落在多波段和准局域环境中的作用。高温超导性早就被预测会发生在氢的金属相中，最近又出现在以氢为主的金属合金中。进一步发展这类体系的理论似乎是有秩序的，特别是探索可能伴随亚晶格熔化的进一步排序的可能性。对于纯氢本身，已经预测了液态金属（近）基态的超流体和超导性共存，现在将理论扩展到液态金属氘所体现的混合对称系统是一个有趣的途径，再次着眼于实验实现。由外加磁场或旋转引起的涡旋特性可能是不寻常的。在电子术语中，所有这些系统都是高度非齐次的，正如尖定理所保证的那样，并且还建议进一步发展加权密度和相关方法，以达到相关电子结构的密度泛函观点，无论是能量学还是有效相互作用。非技术总结：该奖项支持凝聚态物理学的理论研究和教育，主要关注轻元素，包括极端压力和温度下的氢。在之前的一个奖项中，PI预测当这些系统暴露在磁场中或旋转时，会出现新的超导和超流体状态。这项工作的一个关键特征是可以在实验中观察到的关键特征的预测。尽管在巨大压力下的氢存在于我们太阳系的各个地方以及宇宙的其他地方，但实验高压技术的最新进展表明，发现具有潜在技术应用前景的令人兴奋的物质新相已经指日可待。其中一种可能性是在高压下轻元素在高温下产生超导态。PI将继续并扩展他的理论工作，以预测和探索可能在看似最简单的元素中出现的物质的新状态。高压下氢和氢优势金属合金将是研究的重点。这项研究可能会对其他学科产生影响，并将为未来的科学家提供一个培训基地。