Structural effects on excited-state interactions

We use advanced bandstructure methods to study the effect of structural modifications on excited-state dynamics in materials.

One of our main research interests is studying the effect of atomic defects in 2D systems. The defects act as structural perturbations and break the system symmetry by charge localization. Such localization leads to flat electron and hole bands in k-space, which vary the low-energy excitonic transitions and allow a highly controllable exciton nature and lifetime, depending on defect type. In our recent work, we studied defect effects on exciton transitions and valley selectivity in monolayer transition metal dichalcogenides (TMDs), using the GW-BSE approach. Within several collaborations with experimental groups, we further explored methods for defect identification and detected related optical properties and their relation to defect nature. Our current interest is in relating defect localization nature with extended exciton lifetimes. In recent collaborations, we explored the effect of defect type on emission lifetime, with relation to the underlying valley selectivity. We are currently developing ab initio approaches to evaluate the associated lifetimes and their structural dependencies from theory.

Another main research direction is the study of heterostructures, where the excitonic nature varies due to an interface composition. We explore the effect of a dielectric substrate on exciton properties and dynamics in various types of heterostructures, including combinations of semiconductors- and specifically molecular crystals and TMDs, with metals and semi-metals interfaces. In a recent collaboration, we studied how a trilayer TMD heterostructure influences exciton-exciton interaction nature and the resulting emission lifetime. The study of exciton decay across various type of heterojunction is currently a mani topic of study in our group.