Theory of Excitons in 2D Materials -- Valley-Spin Physics, Photoemission Spectra, and Topological Effects

Prof. Ting Cao (Hosted by Yang), University of Washington

The research on atomically thin 2D materials has opened up opportunities in exploring new phenomena and properties as well as related applications absent in conventional bulk materials. In this talk, we will present our recent theoretical and computational studies of excitons in 2D
semiconductors. In the first part, we demonstrate the presence of a series of valley-spin polarized excitons in monolayer transition metal dichalcogenides. We then present our recent study of the pump-probe photoemission spectra of low-dimensional materials. By ab initio calculations based on many-body perturbation theories, we find the photoelectrons from the excitons hold unique energy dispersions and spectra weights, which unveil the fundamental physical properties of the excited states. In the second part, we demonstrate the unusual optical selection rules resulting from topological band effect. We further connect our theoretical discoveries to experimental results and explore their potential applications.