For the Mott insulator state of the Fermi-Hubbard model in the strong-coupling limit, we study the interaction between quasi-particles in the form of doublons and holons. Comparing different methods -- the hierarchy of correlations, strong-coupling perturbation theory, and exact analytic solutions for the Hubbard tetramer -- we find an effective interaction between doublons and/or holons to linear order in the hopping strength T which can display attractive as well as repulsive contributions, depending on the involved momenta. Finally, we speculate about the implications of our findings for high-temperature superconductivity.
@article{arxiv.2304.03034,
title = {Attraction versus repulsion between doublons or holons in Mott-Hubbard systems},
author = {Friedemann Queisser and Gernot Schaller and Ralf Schützhold},
journal= {arXiv preprint arXiv:2304.03034},
year = {2023}
}