Simulations of Strongly Correlated Materials

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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.***