Multichannel Dyson equations for even- and odd-order Green's functions: application to double excitations
Abstract
We extend the concept of the multichannel Dyson equation that we have recently derived to model photoemission spectra by coupling the one- and the three-body Green's functions, to higher-order Green's functions and to other spectroscopies. We show the general structure of the equations and how one can systematically approximate the corresponding multichannel self-energy. As a particular case, we focus on the coupling of the two-body and the four-body Green's functions in the electron-hole channel to describe neutral excitations. This formulation allows for the description of important many-body effects, such biexcitons, in a natural way. We illustrate our approach by applying it to a two-level model system, which, in a one-particle picture, exhibits single and double excitations. Our method can correctly describe both kinds of excitation, unlike standard approaches, and in good agreement with the exact results.
Keywords
Cite
@article{arxiv.2501.04176,
title = {Multichannel Dyson equations for even- and odd-order Green's functions: application to double excitations},
author = {Gabriele Riva and Théodore Fischer and Stefano Paggi and J. Arjan Berger and Pina Romaniello},
journal= {arXiv preprint arXiv:2501.04176},
year = {2025}
}