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. ***
