Electron-Photon Exchange-Correlation Approximation for QEDFT

• URL: http://arxiv.org/abs/2402.09794v1
• Date: Thu, 15 Feb 2024 08:50:36 GMT
• Title: Electron-Photon Exchange-Correlation Approximation for QEDFT
• Authors: I-Te Lu, Michael Ruggenthaler, Nicolas Tancogne-Dejean, Simone Latini, Markus Penz, Angel Rubio
• Abstract summary: Quantum-electrodynamical density-functional theory (QEDFT) provides a promising avenue for exploring complex light-matter interactions. An approximation for the electron-photon exchange-correlation potential is needed. Here we consider this QEDFT functional approximation from one to three-dimensional finite systems.
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• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum-electrodynamical density-functional theory (QEDFT) provides a promising avenue for exploring complex light-matter interactions in optical cavities for real materials. Similar to conventional density-functional theory, the Kohn-Sham formulation of QEDFT needs approximations for the generally unknown exchange-correlation functional. In addition to the usual electron-electron exchange-correlation potential, an approximation for the electron-photon exchange-correlation potential is needed. A recent electron-photon exchange functional [C. Sch\"afer et al., Proc. Natl. Acad. Sci. USA, 118, e2110464118 (2021), https://www.pnas.org/doi/abs/10.1073/pnas.2110464118], derived from the equation of motion of the non-relativistic Pauli-Fierz Hamiltonian, shows robust performance in one-dimensional systems across weak- and strong-coupling regimes. Yet, its performance in reproducing electron densities in higher dimensions remains unexplored. Here we consider this QEDFT functional approximation from one to three-dimensional finite systems and across weak to strong light-matter couplings. The electron-photon exchange approximation provides excellent results in the ultra-strong-coupling regime. However, to ensure accuracy also in the weak-coupling regime across higher dimensions, we introduce a computationally efficient renormalization factor for the electron-photon exchange functional, which accounts for part of the electron-photon correlation contribution. These findings extend the applicability of photon-exchange-based functionals to realistic cavity-matter systems, fostering the field of cavity QED (quantum electrodynamics) materials engineering.

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