NONTECHNICAL SUMMARY This award supports research and education towards understanding the role of light and interactions in the behavior of electrons in a new type of materials called topological insulators. In these materials, even though their interior behaves like a typical insulator, their surfaces allow the flow of electrons in an electrical current. The PI will investigate the effects of shining light on topological insulators, which results in the creation of new composite particles. The project will also examine the fundamental nature of interacting electrons in topological substances in two different regimes: The diffusive regime, where electrons propagate as overlapping waves; and the hydrodynamic regime, where electrons collide against each other so frequently that they flow as a viscous stream of water. Theoretical advances from this award may help the development of new electronic devices that operate through the coupling of light with topological matter. The PI will perform outreach to undergraduate students within the NSF sponsored REU program at OU and will offer public lectures at the Osher Longlife Learning Institute, which organizes a successful program of public lectures. The PI will also offer public lectures to high schools in the Oklahoma City area. TECHNICAL SUMMARY This award will advance our fundamental understanding of the interplay of quantum geometry, band topology, and interactions in electron systems. This project is organized