Simulations of Strongly Correlated Materials

0073308Jarrell这项拨款支持强关联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以及一种新的技术来求解，该新技术通过将晶格问题映射到有限大小的自洽嵌入的团簇上来系统地将非局域修正结合到动态平均场理论中。这种动态团簇近似(DCA)在逆团簇大小中是完全因果的和系统的，它设置了动态位置间关联的最大长度。有效团簇问题可以用微扰理论或量子蒙特卡罗等传统方法来解决。然而，正如在使用动力学平均场理论的计算中一样，DCA计算仍然处于热力学极限。因此，DCA和有限尺寸计算的结果是互补的。量子蒙特卡罗模拟的结果被解析地延续到实频率，使用最大熵方法。这些结果将与解析和数值近似以及实验进行比较。为了获得与实验更直接相关的结果，还将开发一种结合LDA和DCA的技术。这项研究有两个主要目的。第一是从实验和理论上更准确地计算模型体系的有关性质。第二个是探索这些模型的非摄动区，以预测新的物理现象。这项研究的结果应该有助于更好地理解强关联电子系统。这笔拨款支持对强关联电子系统性质的理论研究。所使用的技术既有解析的，也有数值的，研究这些系统的新方法将被开发出来。强关联电子系统包括高温超导体、重费米子材料、非费米液态金属和磁性材料。因此，虽然要解决的问题具有重大的根本性意义，但它们也包含许多具有实际意义的材料。

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.***