Strong coupling quantum electrodynamics Hartree-Fock response theory

TL;DR

This paper advances the SC-QED-HF method by implementing response theory, enabling better understanding of molecular polaritons and revealing electron-photon correlation effects on excitation energies.

Contribution

It develops the response theory for the strong coupling quantum electrodynamics Hartree-Fock model, enhancing its capability to analyze light-matter interactions.

Findings

Electron-photon correlation causes an excitation redshift.

The dipole self-energy significantly affects state properties.

Comparison shows differences with time-dependent QED-HF energies.

Abstract

The development of reliable ab initio methods for light-matter strong coupling is necessary for a deeper understanding of molecular polaritons. The recently developed strong coupling quantum electrodynamics Hartree-Fock model (SC-QED-HF) provides cavity-consistent molecular orbitals, overcoming several difficulties related to the simpler QED-HF wave function. In this paper, we further develop this method by implementing the response theory for SC-QED-HF. We compare the derived linear response equations with the time-dependent QED-HF theory and discuss the validity of equivalence relations connecting matter and electromagnetic observables. Our results show that electron-photon correlation induces an excitation redshift compared to the time-dependent QED-HF energies, and we discuss the effect of the dipole self-energy on the ground and excited state properties with different basis sets.