Phonon screening of excitons in atomically thin semiconductors*

Atomically thin semiconductors, which encompass both 2D materials and quantum wells, have gained significant attention due to their distinct enhancement of excitonic effects resulting from geometric confinement. They serve as key platforms for exploring and utilizing excitons. In theoretical investigations, the ab initio Bethe-Salpeter equation (BSE) is widely used to calculate excitonic properties in these materials. Nonetheless, the majority of BSE calculations neglect the inclusion of phonon screening, leading to limited accuracy in predicting crucial parameters, such as exciton binding energy.

 

Recently, a novel formalism which incorporates phonon screening in the BSE framework has been developed [1]. We apply a recent implementation [2] of this approach to atomically thin semiconductors, revealing the tunability of exciton phonon screening through structural engineering. We provide microscopic analysis on the contributions of different phonon modes to exciton screening. Furthermore, our work uncovers a previously unaddressed phonon screening mechanism, involving phonons in the surrounding material. Our findings provide a comprehensive understanding of the relationships between structural properties, phonon characteristics, and exciton properties in heterostructures consisting of atomically thin semiconductors.