9870681 Fertig The PI plans to investigate how orderly spatially modulated structures in two dimensions interact with a pinning potential. Pinning potentials include impurities and artificial materials patterns and structures. A major fraction of the proposed work is concerned with the electron gas in two dimensions. The study focuses on three areas: the response of spin textures in quantum Hall systems to an array of artificial structures, the response of pinned Wigner crystals to low frequency electromagnetic fields, and the role of plastic deformation on pinning processes in vortex lattices that occur in superconductors. %%% This research is at the forefront of condensed matter theory and is concerned with how electrons confined to a plane and composite particles made up of electrons that participate in a spatially ordered state, respond to defects such as impurities and artificial structures. These problems represent new challenges to theoretical descriptions of layered materials and electronic phenomena that occur in materials and at interfaces of materials. The PI's work will contribute to developing new methods to understand electronic phenomena that occur in materials and that are potentially important in developing new device technologies. ***