U.S.-Federal Republic of Germany Cooperative Research: Microscopic and Phenomenological Theories of Correlated Fermi Systems

美德合作研究：相关费米系统的微观和唯象理论

• 批准号: 8922642
• 负责人: Peter Hirschfeld
• 金额: $ 1.45万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-09-01 至 1994-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8922642&HistoricalAwards=false
• 关键词: U.S.; Federal; Republic; Germany; Cooperative

This award supports Professors P. J. Hirschfeld and K. A. Muttalib of the University of Florida to maintain collaborative research links with Dr. Peter Woelfle of the Institute for Condensed Matter Theory of the University of Karlsruhe, Federal Republic of Germany. They plan to investigate superconductivity and magnetism using the single band Hubbard model, which is possibly relevant to materials with high superconducting transition temperatures ("high-Tc materials.") They will apply two new methods that they recently developed: 1) a new functional integral approach, and 2) a conserving slave boson diagrammatic expansion, to study several questions related to the possibility of superconductivity in Hubbard-like systems, the stability of the Fermi liquid state in the presence of strong correlations, and the stability of incommensurate antiferro- magnetic phases. They will also study models of unconventional superconductivity, with an emphasis on the question of how the symmetry of an unconventional order parameter can be determined with external probes, particularly electromagnetic ones. Although the mechanisms responsible for pairing in the high temperature superconductors remain mysterious even after two years of intense research since its discovery, there is accumulating evidence that electronic correlations, rather than electron-phonon interaction play a crucial role. Unfortunately, there is no adequate systematic and controlled method available for dealing with such strongly correlated systems. New methods such as those being used here are essential for the study of all highly correlated Fermi systems, and should be generally applicable to any similar model, including that appropriate for the high-Tc materials. These novel methods originated as a result of extensive collaboration among these scientists when Dr. Woelfle spent several years at the University of Florida. Continuing the interaction should prove to be very productive and mutually beneficial.

该奖项支持佛罗里达大学的P. J. Hirschfeld教授和K. A. Muttalib教授与德意志联邦共和国卡尔斯鲁厄大学凝聚态理论研究所的Peter Woelfle博士保持合作研究联系。他们计划使用单波段哈伯德模型来研究超导性和磁性，这可能与具有高超导转变温度的材料（“高tc材料”）有关。他们将应用他们最近开发的两种新方法：1)一种新的泛函积分方法，以及2)一个守恒的从属玻色子图展开，来研究与类哈伯德系统中超导的可能性、强相关存在下费米液态的稳定性以及不相称的反铁磁相的稳定性有关的几个问题。他们还将研究非常规超导的模型，重点是如何用外部探针，特别是电磁探针来确定非常规有序参数的对称性。尽管高温超导体中的配对机制在发现后的两年密集研究之后仍然是神秘的，但越来越多的证据表明，电子相关性而不是电子-声子相互作用起着至关重要的作用。不幸的是，没有足够的系统和可控的方法可用于处理这种强相关系统。这里使用的新方法对于研究所有高度相关的费米系统是必不可少的，并且应该普遍适用于任何类似的模型，包括适用于高tc材料的模型。这些新颖的方法起源于沃尔弗尔博士在佛罗里达大学的几年里，这些科学家之间广泛合作的结果。继续这种互动应该证明是非常富有成效和互利的。