Light-Matter Interactions.
Johannes’ research interest focuses on the interdisciplinary area of light-matter interactions. At the interface of material science, quantum optics, and quantum chemistry, exciting new phenomena have been recently experimentally realized. From the strong-coupling of chemical systems in optical cavities (QED Chemistry), the single-molecule strong-coupling to plasmonic nanocavities, single-molecule optomechanics, the condensation of exiton-polaritons, or correlated spectroscopy, a better theoretical understanding is necessary to fully understand and utilize the complex interplay of light and matter.

Single-molecule Strong Coupling.
By coupling molecular systems to plasmonic nanoparticles, single-molecule strong-couling light-matter coupling is archived. In this regime, the strong coupling gives rise to large Rabi splitting, optomechanical features, and can modify photochemistry.

Chemical Systems in Optical Cavities (QED Chemistry). To simulate chemical systems in optical cavities, we employ the cavity Born-Oppenheimer approach (CBOA) allowing for the simulation of the molecular dynamics (MD). Such simulations allow to understand the change of chemical reactions in optical cavities. By using the cavity as catalyst in the reaction novel reaction pathways become possible in the strong-coupling regime.

Quantum-electrodynamical density-functional theory (QEDFT).To simulate such systems, Johannes is interested in method development, where we e.g. contribute to QEDFT that combines traditional density-functional theory (DFT) with quantum photons. For QEDFT, we are interested in approximations for the exchange-correlation functionals, excitation energies using linear-response theory, and the semiclassical approximation.

High-performance Computing. We perform large-scale numerical calculations using ab-initio codes, e.g. octopus code, and CP2K and utilizing the power of graphical processing units (GPUs).