We present a generic procedure for quantifying the interplay of electronic and lattice degrees of freedom in photo-doped insulators through a comparative analysis of theoretical many-body simulations and time- and angle-resolved photoemission spectroscopy (TR-ARPES) of the transient response of the candidate excitonic insulator Ta2NiSe5. Our analysis demonstrates that the electron-electron interactions dominate the electron-phonon ones. In particular, a detailed analysis of the TRARPES spectrum enables a clear separation of the dominant broadening (electronic lifetime) effects from the much smaller bandgap renormalization. Theoretical calculations show that the observed strong spectral broadening arises from the electronic scattering of the photo-excited particle-hole pairs and cannot be accounted for in a model in which electron-phonon interactions are dominant. We demonstrate that the magnitude of the weaker subdominant bandgap renormalization sensitively depends on the distance from the semiconductor/semimetal transition in the high-temperature state, which could explain apparent contradictions between various TR-ARPES experiments. The analysis presented here indicates that electron-electron interactions play a vital role (although not necessarily the sole one) in stabilizing the insulating state.
@article{arxiv.2112.06298,
title = {Unveiling the underlying interactions in Ta2NiSe5 from photo-induced lifetime change},
author = {Denis Golez and Sydney K. Y. Dufresne and Min-Jae Kim and Fabio Boschini and Hao Chu and Yuta Murakami and Giorgio Levy and Arthur K. Mills and Sergey Zhdanovich and Masahiko Isobe and Hidenori Takagi and Stefan Kaiser and Philipp Werner and David J. Jones and Antoine Georges and Andrea Damascelli and Andrew J. Millis},
journal= {arXiv preprint arXiv:2112.06298},
year = {2022}
}