Many-body effects on exciton dynamics in layered heterostructures

Optical excitations in semiconductors have the potential of forming long-lived excitons, coupled electron-hole pairs, serving as key ingredients in efficient light harvesting and optical information science. The stability and coherence of these excitations is strongly coupled to the underlying material structure and can thus be largely designed. Such design principles are of great interest in layered heterostructures, with multiple emerging experiments showing controllability of exciton relaxation lifetimes and mechanisms as a function of layer composition and interlayer commensuration. In this talk I will describe our theoretical research on the underlying interactions responsible for these relaxation processes from first principles. Using the example of transition metal dichalcogenide (TMD) hetero-bilayers, I will discuss structural dependencies of the exciton optical and spin selection rules from a many-body perspective and their huge implications on light absorption. I will further present the case of TMD-Graphene interfaces, where large exciton hybridization occurs due to strain-induced symmetry breaking which is tunable through interlayer twisting. Finally, I will present our new first-principles approach to exciton interaction dynamics resulting from these properties, supplying new understanding of the relation between the underlying material structure and exciton coherence.