Theory and First-Principle Calculation of Photoemission Spectra from Optically Excited States

The behaviors of optically excited states, such as excitons, not only give rise to a variety of fascinating phenomena in condensed matter, but also play vital roles in modern optoelectronics and energy harvesting. In this talk, I will present our recent development on the theory and first-principle methods in the study of the photoemission spectra of low-dimensional materials. By performing calculations based on many-body perturbation theories, we show that, in monolayer transition metal dichalcogenides, the excitons hold unique energy dispersions and spectra weights in photoemission, which unveil the fundamental physical properties of these excited states. We further connect our theoretical works to experimental results and explore their potential applications in other systems.