Joint Theory Seminar of European XFEL, CFEL & University of Hamburg

How photons change the properties of matter

by Michael Ruggenthaler (MPSD, Hamburg)

E1.172 (XHQ)



In this talk I will present a brief overview of how the standard description of quantum chemistry and material sciences have to be adapted when photons become important in correlated light-matter problems [1,2], and possible ways to tackle such situations with ab-initio methods [3-6]. I will highlight that quantum-electrodynamical density-functional theory [3,5], an exact quantum-fluid reformulation of quantum electrodynamics, is a natural framework to determine equilibrium as well as non-equilibrium properties of coupled matter-photon systems, such as new composite (fermionic/bosonic) quasi-particles [1,2], changes in the Born-Oppenheimer surfaces and in chemical reactions [1,2], the emergence of collective effects or changes in the intrinsic lifetimes [7], from first principles. [1] M. Ruggenthaler, N. Tancogne-Dejean, J. Flick, H. Appel, and A. Rubio, "From a quantum-electrodynamical light-matter description to novel spectroscopies", Nature Reviews Chemistry 2, 0118 (2018). [2] J. Flick, M. Ruggenthaler, H. Appel, and A. Rubio, "Atoms and molecules in cavities, from weak to strong coupling in quantum-electrodynamics (QED) chemistry", Proceedings of the National Academy of Sciences 114 (12), 3026-3034 (2017). [3] M. Ruggenthaler, J. Flick, C. Pellegrini, H. Appel, I.V. Tokatly, and A. Rubio, "Quantum-electrodynamical density-functional theory: Bridging quantum optics and electronic-structure theory" Physical Review A 90 (1), 012508 (2014). [4] J. Flick, M. Ruggenthaler, H. Appel, and A. Rubio, "Kohn–Sham approach to quantum electrodynamical density-functional theory: Exact time-dependent effective potentials in real space", Proceedings of the National Academy of Sciences 112 (50), 15285-15290 (2015). [5] M. Ruggenthaler, "Ground-state quantum-electrodynamical density-functional theory", arXiv:1509.01417 (2017). [6] C. Schaefer, M. Ruggenthaler, and A. Rubio, "Insights from ab-initio non-relativistic quantum electrodynamics: Bridging quantum chemistry and quantum optics", arXiv:1804.00923 (2018). [7] J. Flick, D.M. Welakuh, M. Ruggenthaler, H. Appel, and A. Rubio, "Light-Matter Response Functions in Quantum-Electrodynamical Density-Functional Theory: Modifications of Spectra and of the Maxwell Equations", arXiv:1803.02519 (2018).