Theoretical predictions of excited-state phenomena in complex materials can lead to a better understanding of nanoscale energy conversion mechanisms, and of the excitonic properties dominating these processes. Structural complexities, such as reduced dimensionality, interface composition, and the presence of impurities, are closely coupled to underlying exciton interactions and their decay processes. In this talk, I will describe our computational study of the excitonic phenomena in materials of structural complexity, using many-body perturbation theory within the GW and Bethe-Salpeter equation (GW-BSE) approach. I will discuss the effect of heterostructures and atomic defects on exciton properties in layered transition metal dichalcogenides, where a mixed nature of the electron-hole interactions leads to unique optical signatures and structurally tunable selection rules. I will further present a new approach relating the exciton bandstructure and its propagation properties and demonstrate how non-analytical discontinuities in exciton dispersion, typical in systems of reduced dimensionality, lead to unexpected features in the exciton relaxation.

Structural effects on exciton decay processes in functional materials

ACS Fall 2021

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