Applications of Series-Expansion Methods to Many-Body Physics

9318537辛格这个理论和计算密集型的研究将使用系列扩展方法来研究凝聚态物理学中当前感兴趣的各种问题。 主要研究者已经开发了基本的方法来生成系列扩展的量子磁体，强关联费米系统的模型，以及无序系统，如自旋玻璃。 对于这些系统，已获得的系列展开的统一的热力学量，静态响应函数，波矢量相关的等时自旋和电荷相关函数和动力学相关函数的频率矩。 一个主要的焦点将是了解高温超导铜氧化物的正常状态的性质。 结果将比较这些材料的实验，如核磁共振，中子和光散射，光电发射和运输现象。 近藤晶格和哈伯德模型在非二分晶格上的研究将深入了解电子相关驱动的金属-绝缘体转变。 其他系统的研究包括随机量子系统中的临界现象，在挫折自旋模型和共形不变性的二维不可积统计模型的有序。 %此更新补助金将使用系列扩展技术，这最初是为相变的研究开发的，并将其应用于涉及强相关材料的问题。 首席研究员采取的方法有些独特，并补充了用于研究这些问题的其他计算技术。 需要研究的问题包括高温超导体、磁性材料和金属-绝缘体转变。 ***

9318537 Singh This theoretical and computationally-intensive research will use series expansion methods to investigate a variety of problems of current interest in condensed matter physics. The principal investigator has developed the basic methodology to generate series expansions for quantum magnets, for models of strongly correlated Fermi systems, and for disordered systems such as spin glasses. For these systems, series expansions have been obtained for uniform thermodynamic quantities, for static response functions, for wave- vector dependent equal-time spin and charge correlation functions and for frequency moments of dynamical correlation functions. A major focus will be to understand the normal state properties of high temperature superconducting cuprates. Results will be compared to experiments on these materials such as nuclear magnetic resonance, neutron and light scattering, photoemission, and transport phenomena. The Kondo lattice and Hubbard models on non- bipartite lattices will be studied to gain insight into the electron-correlation driven metal-insulator transition. Other systems to be studied include critical phenomena in random quantum systems, ordering in frustrated spin models and conformal invariance in two-dimensional non-integrable statistical models. %%% This renewal grant will use series expansion techniques, which were originally developed for the study of phase transitions, and apply them to problems involving strongly correlated materials. The approach taken by the principal investigator is somewhat unique and complements other computational techniques used to study these problems. The problems to be studied include the high temperature superconductors, magnetic materials and the metal-insulator transition. ***