Research Areas
Quantum Dynamics at the Exponential Barrier
Quantum dynamics scales exponentially with respect to the number of degrees of freedom. In other words, using classical computers, one will eventually hit an exponential wall as the system size increases. There are different ways to cope with this situation, and in our group, we develop and/or apply the following strategies: Firstly, one can reduce the base of the scaling law by choosing optimised, compact basis sets for wave packet expansion (⇨ MCTDH). Secondly, one is often only interested in a few degrees of freedom, which can be targeted using spectroscopic methods, for example. In this case, density matrix theory can be used to describe the influence of the environment by means of dissipation operators (⇨ RDM). Thirdly, quantum-classical and trajectory-based quantum methods are not limited by exponential scaling, but retaining phase information poses a challenge (⇨ Trajectory).
Exciton Dynamics
In photosynthesis, light harvesting utilises electron-hole pairs (Frenkel excitons) to transport the energy of absorbed photons from pigment-protein antenna complexes to reaction centres, where charge separation occurs. The interaction with nuclear degrees of freedom is central to the process. Efficient transport is achieved through the intricate interplay of Frenkel exciton delocalisation and phase and energy relaxation due to exciton-vibrational interaction. Structure and function of photosynthetic light-harvesting complexes were tailored by evolution. Learning the underlying mechanistic principles, artifical solar-energy materials for efficient light-harvesting or exciton transport are being investigated.
Molecules at Interfaces
The interface between inorganic and organic materials provides opportunities by combining the best of both worlds into materials with improved or novel physical properties. One particular challenge in this regard is predicting and characterising the morphology of an organic layer when it interacts with inorganic surfaces via weak van der Waals forces. The photophysics of such hybrid interfaces reflects intricate electronic couplings that can be tuned by external parameters such as strain.
Environmental Physics
Soil is a critical component of our ecosystem. It is under increasing stress due to agricultural activities and environmental pollution. Understanding the physicochemical processes in soil at an atomistic level is challenging due to its heterogeneous, multi-component composition. Alongside experiments, well-characterised models are studied using classical statistical mechanics methods to capture real-life conditions. Our research addresses key questions such as the mobility and thus availability of phosphates (⇨ Phosphates), and the fate of pollutants such as POPs and nanoplastic (⇨ Pollutants).