Dresden 2026 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 13: 2D Materials III – Interlayer excitons
HL 13.3: Talk
Monday, March 9, 2026, 17:15–17:30, POT/0081
Exciton-Exciton Interactions in Van der Waals Heterobilayers — •Tommy Schulz1, Alexander Steinhoff2, and Frank Jahnke1 — 1University of Bremen, Bremen, Germany — 2Carl von Ossietzky University Oldenburg, Oldenburg, Germany
Optically excited van der Waals heterobilayers hosting long-lived interlayer excitons provide a compelling platform for exploring correlated electronic states. In this work, we compute the exciton energy shift as a function of excitation density and temperature. This shift arises from a subtle interplay of various many-body interaction processes, each of which contributes either a blue- or a redshift, corresponding to repulsive or attractive interactions, respectively. By incorporating the fermionic substructure of excitons as well as dynamical screening effects, we show that the commonly assumed dominant repulsive dipole-dipole interaction is almost perfectly compensated. This finding challenges the simple picture of a purely bosonic exciton gas. Moreover, we identify a crossover from attractive to repulsive behavior at elevated exciton densities. Comparing these results - obtained using first-principle band structures and Coulomb matrix elements - with those from a simpler two-band model highlights the importance of a material-realistic description of the electronic states.
Keywords: Heterobilayers; many-body effects; exciton-exciton interaction; 2D materials