CAREER: Topological Excitations in Two Dimensional Systems

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Murphy 9733949 This is a CAREER Award to a female scientist. The research deals with special types of electronic excitations which occur as spatially extended quasiparticles in two-dimensional electron systems. It is often advantageous to sort such excitations according to whether or not they have a non-zero winding number or twist. Excitations possessing a twist are known as "topological excitations" and include solitons, vortices, domain walls and dislocations. They cannot decay for the same reason you cannot untwist a phone cord without picking up the receiver: the excitation or winding can only be removed by a large scale reorientation of the entire system. This translates to long term stability as evidenced by the use of a topological excitation known as a soliton as a signal carrier in transcontinental fiber links. The concept of a topological excitation has proven exceptionally useful in physics: Rather than attempt to describe the behavior of the entire system, a more manageable approach focuses on just the stable configuration of these excitations. Thus the tornadoes in a storm, the dislocations in a crystal or the domain walls in a ferromagnet are studied to obtain a great deal about the system at hand. This proposal details an extensive study of the topological excitations occurring on two-dimensional electronic systems in a magnetic field. %%% This is CAREER Award to a female scientist. The research deals with special types of electronic excitations known as topological excitations. These excited electron states possess a kind of twist, like a screw. Previously studied as mathematical oddities, they have recently been found in nature in two-dimensional semiconductor structures, known as Quantum Hall systems. These stable excitations are more than a new language for many body electron interactions, they are real spatially extended quasiparticles. The experimental goal of this proposal is a greater understanding of the role of topological excitations in two dimensional electronic systems. The second focus of this CAREER proposal is the adaptation of novel instructional approaches, commonly used at the introductory level, to upper level physics courses. While introductory physics education has benefited from these new techniques, there has been little application to more advanced undergraduate material. The plan is to introduce concept based questions in conjunction with group learning techniques into the more advanced curricula and to facilitate this introduction by the development of a concept question website.