Light–Matter Response in Nonrelativistic Quantum Electrodynamics

ACS Photonics 6,11, 2757 - 2778 (2019)

Light–Matter Response in Nonrelativistic Quantum Electrodynamics

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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Preprint - 3.73 MB
We would like to thank Christian Schäfer and Norah Hoffmann for insightful discussions and Sebastian Ohlmann for the help with the efficient massive parallel implementation. J.F. acknowledges financial support from the Deutsche Forschungsgemeinschaft (DFG) under Contract No. FL 997/1-1, and all of us acknowledge financial support from the European Research Council (ERC-2015-AdG-694097),the Cluster of Excellence ‘Advanced Imaging of Matter’ (AIM), Grupos Consolidados (IT1249-19) and SFB925 “Light induced dynamics and control of correlated quantum systems”.The Flatiron Institute is a division of the Simons Foundation.

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