Photon Many-body Dispersion: an Exchange-correlation Functional for Strongly Coupled Light-matter Systems

Abstract

We introduce an electron-photon exchange-correlation functional for quantum electrodynamical density-functional theory (QEDFT). The approach, photon MBD (pMBD), is inspired by the many-body dispersion (MBD) method for weak intermolecular interactions, which is generalized to include both electronic and photonic (electromagnetic) degrees of freedom on the same footing. We demonstrate that pMBD accurately captures 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 pMBD is computationally efficient and allows simulations of large complex systems coupled to optical cavities.

Figures (2)

• Figure 1: Interaction energy $\Delta E$ comparison of Ar dimer outside (black) and inside the cavity along different polarization directions. In (a), we show the interaction energy $\Delta E$ for different distances between two argon atoms, and polarization along $z$ (red), $x$ (blue) and $y$ (green) direction. In (b), we compare cavity energy results between PBE0-pMBD and QED-CC. For both methods, $\Delta E (R_z) = E (R_z) - E (R_z = 25 \AA)$
• Figure 2: Interaction energy $\Delta E$ comparison of benzene dimer complex and graphene flake outside (black) and inside the cavity with different polarization directions $z$ (red), $x$ (blue) and $y$ (green) direction. In (a), we fix $R_{z}=3.3 \AA$ and change $R_{x}$ values. In (b), we keep two graphene flakes parallel to each other along the $xy$ plane, and change the value of $R_{z}$.