Light-matter interactions determine materials’ functionality in emerging applications, such as energy conversion and storage and quantum information processing. Excitons, correlated electron-hole pairs bound together by a Coulomb interaction, often serve as the main energy carriers, with their lifetime and decay dynamics dominating the energy-transfer efficiency. Low-dimensional excitonic semiconductor systems, such as organic molecular crystals, transition metal dichalcogenides (TMDs), and layered hybrid perovskites, hold strongly-bound, long-lived excitons- a typical feature due the reduced dimensionality. In these materials, structural tunability offers the controllable excited-state setting needed to optimize device functionality. Direct imaging of exciton propagation is possible via advanced ultrafast microscopy, allowing the observation and examination of exciton relaxation and processes through a propagating wavepacket picture, and revealing a wealth of exciton scattering mechanisms and decay pathways.
A key factor that impacts exciton dynamics is structural modifications in the interacting material. Local structural effects, such as atomic defects, heterostructure compositions, and crystal fluctuations, can vastly increase carrier mobility, allowing enhanced catalytic and transport activity. A theoretical understanding of such a complex excitonic picture must assess a variety of electron-hole transitions with modified quantum selection rules associated with the structural modifications. Yet, a theory that accounts for the interplay between local modifications of the crystal environment and their effect on exciton relaxation processes is lacking, highlighting the need for a predictive, structure-sensitive theory of the underlying structure-dynamics relations.
This project involves the derivation, implementation, and application of predictive computational and theoretical methods to understand the fundamental dynamics that govern light-matter interactions in materials. We explore emerging low-dimensional semiconducting materials of interest for renewable energy and quantum information science. For these materials, vast experimental data enables careful validation and ultimately the development of a reliable theory, aiming at reaching comprehensive understanding of the relation between the atomistic material structure and the light harvesting efficiency. Specifically, we are deriving and using many-body first-principles approaches to numerically evaluate complex interactions dominating the excited-state dynamical mechanisms involved in the light energy transfer in the material.
Our research is divided to three main parts: derivation of first-principles approaches to excited-state dynamics in materials; application to low-dimensional semiconducting materials of complex structures; and derivation of theoretical extensions beyond common approximations on the interaction strengths. This is achieved within the three objectives discussed below.
