Light–Matter Response in Nonrelativistic Quantum Electrodynamics
journal contributionposted on 29.10.2019, 19:03 by Johannes Flick, Davis M. Welakuh, Michael Ruggenthaler, Heiko Appel, Angel Rubio
We derive the full linear-response theory for nonrelativistic quantum electrodynamics in the long wavelength limit and provide a practical framework to solve the resulting equations by using quantum-electrodynamical density-functional theory. We highlight how the coupling between quantized light and matter changes the usual response functions and introduces cross-correlated light-matter response functions. These cross-correlation responses lead to measurable changes in Maxwell’s equations due to the quantum-matter-mediated photon–photon interactions. Key features of treating the combined matter-photon response are that natural lifetimes of excitations become directly accessible from first-principles, changes in the electronic structure due to strong light-matter coupling are treated fully nonperturbatively, and self-consistent solutions of the back-reaction of matter onto the photon vacuum and vice versa are accounted for. By introducing a straightforward extension of the random-phase approximation for the coupled matter-photon problem, we calculate the ab initio spectra for a real molecular system that is coupled to the quantized electromagnetic field. Our approach can be solved numerically very efficiently. The presented framework leads to a shift in paradigm by highlighting how electronically excited states arise as a modification of the photon field and that experimentally observed effects are always due to a complex interplay between light and matter. At the same time the findings provide a route to analyze as well as propose experiments at the interface between quantum chemistry, nanoplasmonics and quantum optics.
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random-phase approximationmatter-photon responseresponse functionsframeworkmatter changesphoton fieldquantum opticslinear-response theorywavelength limitquantum chemistrynonrelativistic quantum electrodynamicsNonrelativistic Quantum Electrodynamicscross-correlation responsesKey featuresab initio spectraquantized electromagnetic fieldmatter-photon problemquantized lightequationphoton vacuumquantum-electrodynamical density-functional theorycross-correlated light-matter response functions