Exploring gradient-approximated functionals for strongly coupled light-matter systems

Recent theoretical advances have made it possible to use ab initio methods to describe strong-light matter systems from first principles. One of these methods, quantum-electrodynamical density functional theory (QEDFT) is a promising candidate with a low computational cost to allow for computationally efficient simulations with high accuracy. Recently, we have introduced a computational efficient density functional [1] that only depends on the electron density and its gradients for QEDFT. In this work, we explore the accuracy of this functional for realistic multi-mode setups described by macroscopic QED. We study systems, such as interacting molecules strongly coupled to spherical cavities and nanoplasmonic layered systems. In addition, we demonstrate pathways to correctly capture multi-photon processes and anisotropy.

[1] J. Flick, Phys. Rev. Lett. 129, 143201 (2022).