The interaction of light with solids gives rise to new bosonic quasiparticles, with the exciton being---undoubtedly---the most famous of these polaritons. While excitons are the generic polaritons of semiconductors, we show that for strongly correlated systems another polariton is prevalent---originating from the dominant antiferromagnetic or charge density wave fluctuations in these systems. As these are usually associated with a wave vector k=(π,π,…) or close to it, we propose to call the derived polaritons π-tons. These π-tons yield the leading vertex correction to the optical conductivity in all correlated models studied: the Hubbard, the extended Hubbard model, the Falicov-Kimball, and the Pariser-Parr-Pople model, both in the insulating and in the metallic phase.
@article{arxiv.1902.09342,
title = {Generic optical excitations of correlated systems: $\pi$-tons},
author = {Anna Kauch and Petra Pudleiner and Katharina Astleithner and Patrik Thunström and Tin Ribic and Karsten Held},
journal= {arXiv preprint arXiv:1902.09342},
year = {2020}
}