This U.S.-Hungary Joint Fund research project on "Phenomenology and Microscopics of High Temperature Superconductors" will be conducted by Dr. Alfred Zawadowski of E tv s Lorand University in cooperation with Dr. Gergely T. Zimanyi of the University of California Davis. The researchers consider the Marginal Fermi Liquid (MFL) theory one of the most successful phenomenologies for high Tc superconductors. Their early studies explored the importance of higher order perturbative corrections, producing improved agreement with the experiments. They now introduce the notion of the Anti-Ferromagnetic MFL (AF-MFL) theory, the basic assumption of which is that the spin correlations are dominantly anti-ferromagnetic. They will analyze the high order corrections with the help of renormalization group methods, and explore many experimental consequences. On the issue of spin-charge separation, they will address the importance of non-scaling contributions, and the question of a minimal model. The researchers also intend to develop a novel microscopic approach to higher dimensional Luttinger Liquids, based on a well-controlled expansion technique in a model of a two-dimensional wire-mesh. Their initial scaling studies revealed that spin and superconducting fluctuations are the dominant excitations of the model at low temperatures. They will establish their momentum dependence to distinguish between magnetic ordering tendencies and spin-liquid formation. Results should determine experimentally accessible response functions and add to our understanding of the special role of two dimensions in problems of high temperature superconductivity. This research in materials theory fulfills the US-Hungary Joint Fund's objective of advancing science by enabling leading experts in the United States and Hungary to combine complementary talents and pool research resources in areas of strong mutual interest and competence.
