Excited-state propagation and radiative lifetimes from exciton dispersion

Understanding the energetics and dynamics of excited states formed by light-matter interactions is essential for applications across optoelectronics and photophysics. In particular, exciton evolution and decay lifetimes are coupled to optical selection rules, resulting from the atomic structure of the host materials. In this work, we study exciton time propagation and its relation to material structure and dimensionality from ab initio GW-BSE-based computations. We examine four representative systems: solid pentacene, an organic molecular crystal with large excitonic effects; monolayer MoS2, with degenerate excitons in different momentum-space valleys; monolayer black phosphorus, a material exhibiting linear dichroism; and (8,0) single-walled carbon nanotube, a prototypical quasi-1D system. We explore how features of the exciton bandstructure manifest in its time-evolution, evaluate the associated exciton radiative lifetime and investigate thermalization effects.