Young Investigator Group Theory of Electron Dynamics and Spectroscopy

Young Investigator Group

Electrons connect atoms via physical long-range interaction or chemical bonding and define molecular properties including interaction with electromagnetic fields or adjacent electronic systems. Interaction strengths and time determine electronic excitation or ionization. Research focus is laid on quantum and nano-structured material. Method-wise, we employ time-dependent and time-independent theories in their conventional formulation and advance them by quantum computing and artificial intelligence techniques.

Photo- or auto-ionization processes are a hurdle for any theoretical description, because electrons can be bound or in the continuum. We use accurate wavefunction-based methods to investigate second-order ionization processes in which energy transfer among electrons on different subsystems anticipates the ionization (inter-particle Coulombic decay). We showed that it is operative in semiconductor quantum dot arrays as they are integral to quantum dot qubit networks or composite solar cells.

Adjacent chemical systems can also foster an electron transfer after photo-excitation. An example is photo-catalysis with semiconducting nanoparticles as used i.e. in the production of green hydrogen. The processes gains in complexity, when the electron transfer is coupled to a proton transfer or when the electron is solvated into water. Capturing the full situation requires typically multi-scale techniques.

The above processes sensitively depend on the chemical structure of the involved nanoparticles, which is most accurately probed by spectroscopy at different wave lengths, in particular by X-ray absorption and resonant inelastic X-ray scattering. Here we employ and extend linear-response techniques for application in large molecules, nanoparticles, and cluster in solids. Extension is among others by machine-learning techniques, which may find their application in digital twins of spectrometers.