title: Optimized Effective Potential for Quantum Electrodynamical Time-Dependent Density Functional Theory.
abstract: We propose an orbital exchange-correlation functional for applying time-dependent density functional theory to many-electron systems coupled to cavity photons. The time nonlocal equation for the electron-photon optimized effective potential (OEP) is derived. In the static limit our OEP energy functional reduces to the Lamb shift of the ground state energy. We test the new approximation in the Rabi model. It is shown that the OEP (i) reproduces quantitatively the exact ground-state energy from the weak to the deep strong coupling regime and (ii) accurately captures the dynamics entering the ultrastrong coupling regime. The present formalism opens the path to a first-principles description of correlated electron-photon systems, bridging the gap between electronic structure methods and quantum optics for real material applications.
authors.affiliation: Departamento de Fisica de Materiales, Nano-bio Spectroscopy Group and ETSF Scientific Development Centre, Universidad del Pais Vasco UPV/EHU, E-20018 San Sebastian, Spain.
authors.forename: Camilla
authors.initials: C
authors.lastname: Pellegrini
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Flick
authors.affiliation: Departamento de Fisica de Materiales, Nano-bio Spectroscopy Group and ETSF Scientific Development Centre, Universidad del Pais Vasco UPV/EHU, E-20018 San Sebastian, Spain.|IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.
authors.forename: Ilya V
authors.initials: IV
authors.lastname: Tokatly
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.|Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Appel
authors.affiliation: Departamento de Fisica de Materiales, Nano-bio Spectroscopy Group and ETSF Scientific Development Centre, Universidad del Pais Vasco UPV/EHU, E-20018 San Sebastian, Spain.|Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.|Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: Angel
authors.initials: A
authors.lastname: Rubio