Speaker
Description
Exciton dynamics—including ultrafast photogeneration, diffusion, and thermalization—plays a central role in optoelectronic, photovoltaic, and photocatalytic processes. In this talk, I will present a novel first-principles many-body framework for describing exciton dynamics driven by electron–phonon interactions. A key ingredient of the theory is the introduction of an auxiliary excitonic species, referred to as the irreducible exciton, which eliminates the overscreening of the electron–phonon interaction that arises in conventional approaches. The resulting Excitonic Bloch Equations retain a computational cost comparable to that of the widely used Excitonic Boltzmann Equations while providing a unified description of the time evolution of coherent, irreducible, and incoherent excitons during and after optical excitation. As an application, I will discuss the real-time formation of excitons in monolayer WSe2, revealing how above-bandgap photoexcitation initially generates quasi-free electron–hole pairs that are subsequently converted into bound excitons through their interaction with phonons.