Abstract

Excitons—correlated electron-hole pairs generated upon photoexcitation—provide a fundamental framework for describing the low-energy optical excitations in semiconductors and insulators. With continued advances in powerful spectroscopic techniques, we are increasingly able to probe how excitons interact with their environment, especially their coupling to lattice vibrations.

In this seminar, I will present our recent efforts to develop and apply ab-initio methods, grounded in many-body perturbation theory, to study exciton-phonon interactions in emerging materials such as 2D transition metal dichalcogenides. Modeling exciton-phonon interactions in complex materials is challenging due to the delocalized character of exciton states and the concurrent entanglement of their exciton bandstructure. To address this, I will introduce our recent work on maximally localized exciton Wannier functions (MLXWFs). This new formalism provides a compact, real-space representation of exciton states, offering insights into exciton band dispersion and topology and paving the way for scalable modeling of exciton dynamics.

I will demonstrate the utility of this framework through a case study on phonon-driven exciton transport in organic semiconductors, with a particular focus on the polaronic regime, where excitons are trapped by ionic distortions and diffusion occurs via thermally activated hopping. I will conclude with a forward-looking perspective on the wide-ranging potential of MLXW Fs, highlighting their applicability beyond exciton–phonon interactions to a spectrum of challenges in excitonics.