Upper bounds on the charge susceptibility of many-electron systems coupled to the quantized radiation field

TL;DR

This paper extends the Kubo-Kishi theorem to include electron-photon interactions and general Coulomb repulsion, providing new upper bounds on the charge susceptibility of many-electron systems coupled to quantized radiation.

Contribution

It introduces a generalized theorem that accounts for electron-photon interactions and broader Coulomb interactions in charge susceptibility bounds.

Findings

Derived upper bounds on charge susceptibility with electron-photon coupling

Extended the theorem to include non-on-site Coulomb interactions

Enhanced understanding of many-electron systems in quantum radiation fields

Abstract

We extend the Kubo-Kishi theorem concerning the charge susceptibility of the Hubbard model in the following way: (i) The electron-photon interaction is taken into account. (ii) Not only on-site but also general Coulomb repulsion is considered.