QED Chemistry for Real Systems (QEDChem)
Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
Final Report Abstract
During the DFG Research Fellowship ”QED Chemistry for Real Systems” the research fellow Dr. Johannes Flick and his collaborators were able to develop computational first principle methods that describe the dynamics of strongly light-matter coupled systems for the field of QED (polaritonic) chemistry. The field of QED chemistry at the interface of chemistry, material science, condensed matter physics, and quantum optics has surged recently and now opens a new pathway to alter material properties. The strong light-matter coupling gives rise to several exciting phenomena, such as strongly correlated electron-photon bound states, changes in spectroscopic observables, and chemical reactivity and is experimentally realizable with nanoplasmonic setups or optical cavities. Prior computational developments in this field included the studies of effective Hamiltonians and static ab-initio methods. Since chemical reactions involve excited states of matter, it is important to correctly describe not only ground states and static properties, but also the excited-state manifold and the dynamics of the system. In five innovative studies, we extended computational methods to describe the dynamics of coupled light-matter systems from first principles for two important regimes, electronic and vibrational strong coupling, where an electronic or vibrational excitation is in resonance to a mode of the photon field. In the first study, we developed the linear-response framework for correlated matter-photon systems. We find that quantum-matter-mediated interactions among photons change the Maxwell’s equations and therefore first-principle calculations become applicable to situations in which such interactions become dominant. We can predict the intrinsic radiative lifetimes of molecular excitations without the need of artificial baths or post-processing. The formalism can be added in a straightforward way to existing TDDFT linear-response implementations that are available in most of the quantum chemistry codes in the community and has been implemented into the Octopus code, a open-source real-space density-functional theory code. In a second study, we used this framework to construct polaritonic potential-energy surfaces from first principles to study the modification of photochemical reactions under strong light-matter coupling. Potential applications of strong-light matter coupling could be to either directly enhance the efficiency of the reaction, or to quench undesired chemical pathways with the possibility to controllably alter and design potential-energy surfaces. In the third study, we introduce a computational method that can treat coupled electron, nuclear and photonic degrees of freedom from first principles, which is necessary to correctly describe vibrational strong coupling from first principles. In this work we show how to calculate the experimentally observed signatures of polaritonic states in infrared spectra and consider finite temperature effects. The method will be useful to describe the experiment in the field of QED chemistry and answer open questions such as how transition states become altered under strong light-matter coupling. In a fourth study, we introduce a variational wave function based method to calculate the eigenstates of light-matter coupled systems. Using this method, we get access to observables such as the modulation of the cavity mode. We demonstrate that this method serves as a good starting point to analyse systems from the weak to the ultra-strong coupling regime. In a fifth study, we extended our research from finite systems to condensed-matter systems. In this project, we demonstrated the possibilities of strong light-matter coupling to make energy transfer processes seen in the field on nonlinear phononics more efficient. These new concepts in cavity control of nonlinear processes enable a new pathway for quantum optical engineering of new states of matter. Ongoing follow-up projects include a cooperation with the Max Planck Institute for Structure and Dynamics of Matter and Harvard University on the ab-initio simulation of experimental systems and the exploration of utilizing dissipative processes to catalyze photochemical reactions with researchers from Harvard University.
Publications
- Excited-State Nanophotonic and Polaritonic Chemistry with Ab initio Potential-Energy Surfaces
J. Flick, P. Narang
- Light–Matter Response in Nonrelativistic Quantum Electrodynamics. ACS Photonics 6, 11, 2757-2778 (2019)
J. Flick, D. M. Welakuh, M. Ruggenthaler, H. Appel, A. Rubio
(See online at https://doi.org/10.1021/acsphotonics.9b00768) - Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems
N. Tancogne-Dejean, M. J. T. Oliveira, X. Andrade, H. Appel, C. H. Borca, G. Le Breton, F. Buchholz, A. Castro, S. Corni, A. A. Correa, U. De Giovannini, A. Delgado, F. G. Eich, J. Flick, G. Gil, A. Gomez, N. Helbig, H. Hübener, R. Jestädt, J. Jornet-Somoza, A. H. Larsen, I. V. Lebedeva, M. Lüders, M. A. L. Marques, S. T. Ohlmann, S. Pipolo, M. Rampp, C. A. Rozzi, D. A. Strubbe, S. A. Sato, C. Schäfer, I. Theophilou, A. Welden, A. Rubio
(See online at https://doi.org/10.1063/1.5142502) - Variational theory of non-relativistic quantum-electrodynamics. Phys. Rev. Lett. 122, 193603 (2019)
N. Rivera, J. Flick, P. Narang
(See online at https://doi.org/10.1103/PhysRevLett.122.193603)
