Simulating light-matter coupling in realistic cavities with QEDFT

Recent experiments have shown that strong light-matter coupling can significantly influence chemical reactivity, energy transfer, and photochemical processes. One promising theoretical approach to light-matter coupling is quantum-electrodynamical density-functional theory (QEDFT), which extends density-functional theory (DFT) to strongly coupled light-matter systems. The recently introduced photon many-body dispersion (pMBD) functional accounts for anisotropic properties of materials and incorporates long-range correlation energy through higher-order corrections[1]. While QEDFT has advanced understanding of light–matter interactions, existing studies have not incorporated realistic cavity setups. To address this, Svendsen et al. [2] introduced macroscopic-QED (MQED), a framework capturing complex geometries and dissipative effects. We apply QEDFT with pMBD to explore how molecular properties change in realistic cavity setups. Using MQED, we can calculate the coupling strength and mode frequencies of experimentally relevant Fabry–Pérot cavities, allowing us to model observable, tunable effects of strong light–matter coupling. Our results provide a path to quantitatively connecting ab initio theory with polaritonic chemistry experiments.

[1] C. Tasci, L.A. Cunha, and J. Flick, Phys. Rev. Lett., 134, 073002 (2025).

[2] M.K. Svendsen, K.S. Thygesen, A. Rubio, and J. Flick, J. Chem. Theory Comput., 20 (2), 926-936, (2024).