Periodic Photon Many-Body Dispersion: Exchange-Correlation Functional for Materials in Optical Cavities

In polaritonic chemistry, strong light-matter interactions between matter and cavity photons have been experimentally shown to modify physical and chemical properties. Here, of particular interest is the cavity-induced modification to weak inter- and intramolecular interactions. The recent development of the photon many-body dispersion (pMBD) method [1], an exchange-correlation functional in quantum electrodynamical density-functional theory (QEDFT), has made possible the ab initio study of cavity-induced van der Waals interactions for molecules under strong light-matter coupling. We extend the pMBD method to the study of material systems. We then use this extension of pMBD to study bilayer graphene and hBN, along with other heterostructures. We show that pMBD can accurately capture effects that arise in the context of strong light-matter interactions, such as anisotropic electron-photon interactions, beyond single-photon effects, and cavity-modulated van der Waals interactions. Moreover, we show that this extension allows for efficient k-point sampling of the unit cell for the ab initio study of experimentally relevant systems.

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