9520175 Harris This project seeks to understand the roles of symmetries and pseudosymmetries in novel materials. One project concerns the study of the magnetic symmetry of the lamellar copper oxide antiferromagnets, with a goal of accounting for the observed magnetic anisotropy. Since these materials (when suitable doped) give rise to high temperature superconductivity, this research can have technological as well as intellectual payoffs. Another project concerns the symmetry in Kagome antiferromagnets. Such systems are realized in structures in which magnetic ions occupy lattice planes that are widely separated by nonmagnetic ions. The principal investigator will attempt to answer the open question as to whether there is long range order of any type in the quantum ground state. If there is, it would probably involve a totally new and interesting type of symmetry. %%% Symmetries play a crucial role as an aid in interpreting and understanding materials. This research involves work in two projects in which the symmetries involved are not well understood. Both projects concern antiferromagnets, in which magnetic spins do not all align but rather alternate in a regular pattern. The first addresses the magnetic symmetry in lamellar copper oxides, which are materials that give rise to high temperature superconductivity when they are doped. The second concerns the symmetry in a quantum model on a special two dimensional lattice. If long range order is present in this system in the absence of thermal disorder, this would probably involve a totally new and interesting type of symmetry. ***
