Applications of Series-Expansion Methods to Many-Body Physics

9318537辛格这项理论和计算密集的研究将使用级数展开方法来研究当前凝聚态物理中感兴趣的各种问题。首席研究人员已经开发了产生量子磁体、强关联费米系统模型和无序系统(如自旋玻璃)的级数展开的基本方法。对于这些系统，得到了均匀热力学变量、静态响应函数、依赖于波矢的等时自旋和电荷关联函数以及动态关联函数的频率矩的级数展开式。一个主要的焦点将是了解高温超导铜酸盐的正常态性质。结果将与这些材料上的实验进行比较，如核磁共振、中子和光散射、光电发射和传输现象。我们将研究非二分晶格上的Kondo晶格和Hubbard模型，以深入了解电子相关驱动的金属-绝缘体相变。其他要研究的系统包括随机量子系统中的临界现象，受阻自旋模型中的有序，以及二维不可积统计模型中的共形不变性。%续期拨款将使用级数展开技术，这种技术最初是为研究相变而开发的，并将其应用于涉及强关联材料的问题。首席研究人员采取的方法有些独特，是对用于研究这些问题的其他计算技术的补充。需要研究的问题包括高温超导体、磁性材料和金属-绝缘体的转变。***

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. ***