The time-resolved angle-resolved photoemission spectra of WSe2, a paradigmatic transition metal dichalcogenide, are dominated by a transient signal that, after being initially observed in the gap at the K valley, scatters, on an ultra-fast time scale of ∼ 30 fs, to the Σ valley. In this work we question the common interpretation of the experimental dynamics in terms of a massive bound electron-hole exciton that scatters with phonons and behaves as a quasi-particle. By using a combined theoretical and experimental investigation, we demonstrate that the observed dynamics can be interpreted as the photo-induced transition from direct to indirect excitonic-insulating order. The features that appear in the experimental spectrum correspond to single-particle levels renormalized by the excitonic spontaneous polarization.
@article{arxiv.2604.07200,
title = {Excitons in WSe2 time-resolved ARPES: particle or oscillation?},
author = {Kai Wu and Michele Puppin and Andrea Marini},
journal= {arXiv preprint arXiv:2604.07200},
year = {2026}
}