We examine the eigenstates of the one-dimensional Jaynes-Cummings-Hubbard (JCH) model in the two-excitation subspace. We discover that two-excitation bound states emerge when the ratio of vacuum Rabi frequency to the tunneling rate between cavities exceeds a critical value. We determine the critical ratio as a function of the quasi-momentum quantum number, and indicate that the bound states carry a strong correlation in which the two polaritons appear to be spatially confined together.
@article{arxiv.1101.1366,
title = {Two-polariton bound states in the Jaynes-Cummings-Hubbard model},
author = {M. T. C. Wong and C. K. Law},
journal= {arXiv preprint arXiv:1101.1366},
year = {2015}
}