This individual investigator award will provide funds to a senior researcher for a project to investigate the role of defects in two-dimensional phase transitions. The concepts of symmetry, dimensionality, and disorder all are central to the description of phase transitions. It is generally recognized that defects can play a critical role in phase transitions, especially in reduced dimensionality. The combination of the atomic resolution available with the variable-temperature scanning tunneling microscope (STM) coupled with the ability to grow artificially structured two and one-dimension configurations out of equilibrium on a surface promises to change the way we think about the role of defects in phase transitions in reduced dimensionality. This project will utilize a variable-temperature STM, which renders spatial images of the atomic and electronic distributions at the surface as a function of temperature. Surface structure and lattice dynamics will be determined with elastic and inelastic electron scattering as well as surface x-ray scattering. Surface magnetism will be probed with a combination of linear and non-linear magneto-optical Kerr rotation utilizing a newly designed octapole superconducting magnet. Young scientists from the undergraduate through the post-graduate levels will be trained in techniques relevant to future careers in academe, industry, and government laboratories. %%% This individual investigator award will provide funds to a senior researcher for a project to investigate the fundamental role of imperfections or defects in phase transitions for material systems in two dimensions. It is generally recognized that defects can play a critical role in phase transitions, especially in reduced dimensionality. Many potential technological devices utilize the properties of a phase transition in a given material. As the size of devices become smaller, it is important to understand the effect of defects on the phase transitions of these materials of reduced dimension. The impact of this research program will be felt on two fronts. First, these experiments, and the concepts that come from them, may change the way we think about phase transitions in reduced dimensionality. Secondly, and most importantly, is the training of young scientists at the undergraduate, graduate and post-graduate levels in an area supporting our national agenda on nanotechnology. ***
