Simulations of Strongly Correlated Materials

0073308年1月11日该基金支持强相关电子系统的理论研究。 这些系统包括高温超导体、重费米子材料、非费米子液态金属和磁性材料。 这些系统的模型将使用有限大小和动态平均场计算和一种新的技术，系统地将非局部校正的动态平均场理论映射到一个有限大小的自洽嵌入集群的晶格问题来解决。 这个动态集群近似（DCA）是完全因果关系和系统的反集群大小设置的最大长度的动态站点间的相关性。 有效团簇问题可以用传统的方法解决，如微扰理论或量子蒙特卡罗。 然而，在计算采用动力学平均场理论，DCA计算仍然在热力学极限。 因此，DCA和有限尺寸计算的结果是互补的。 从量子蒙特卡罗模拟的结果分析继续使用最大熵方法的真实的频率。 这些结果将进行比较，分析和数值近似和实验。 为了获得与实验更直接相关的结果，还将开发结合LDA和DCA的技术。 这项研究有两个主要目标。 第一个目标是从实验和理论上更精确地计算模型系统的相关性质。 第二是探索这些模型的非微扰区域，以预测新的物理现象。 这项研究的结果将有助于更好地理解强相关的电子系统。%该基金支持强关联电子系统性质的理论研究。 将使用的技术是分析和数值，并将开发新的方法来研究这些系统。 强关联电子系统包括高温超导体、重费米子材料、非费米子液态金属和磁性材料。 因此，虽然要处理的问题具有重大的根本重要性，但它们也包括许多具有实际重要性的材料。

0073308JarrellThis grant supports theoretical research on strongly correlated electronic systems. Such systems include the high temperature superconductors, heavy Fermion materials, non-Fermi liquid metals and magnetic materials. Models of these systems will be solved using finite-sized and dynamical mean field calculations and a novel tecnique which systematically incorporates non-local corrections to the dynamical mean field theory by mapping the lattice problem onto a finite-sized self-consistently embedded cluster. This Dynamical Cluster Approximation (DCA) is fully causal and systematic in the inverse cluster size which sets the maximum length of the dynamical intersite correlations. The effective cluster problem may be solved with conventional techniques such as perturbation theory or quantum Monte Carlo. However, as in calculations employing the dynamical mean field theory, the DCA calculations remain in the thermodynamic limit. Thus results from the DCA and finite-size calculations are complementary. Results from quantum Monte Carlo simulations are analytically continued to real frequencies using the maximum entropy method. These results will be compared to analytic and numerical approximations and experiment. To obtain results more directly relevant to experiment, a technique which combines LDA and DCA will also be developed. This study has two main objectives. The first is to calculate experimentally and theoretically relevant properties of model systems more accurately than heretofore possible. The second is to explore the non-perturabative regions of these models in order to predict new physical phenomena. The results of this study should lead to a better understanding of strongly correlated electronic systems.%%%This grant supports theoretical research on the properties of strongly correlated electronic systems. The techniques to be used are both analytical and numerical, and new methods to study these systems will be developed. Strongly correlated electronic systems include the high temperature superconductors, the heavy Fermion materials, the non-Fermi liquid metals and magnetic materials. Thus, while the issues to be addressed are of great fundamental importance, they also encompass many materials of practical importance.***