Electrondynamics of Ultrafast Energy Transfer Processes Induced by Long-Range Electron Correlation

It is widely known that electrons are indistinguishable particles and thus each electron can be in any position in an atom or molecule. Moreover, electrons know of each other, i.e. they are correlated. Electron correlation is a long-range effect which can couple two electrons with each other, even if they are located in different atoms or molecules separated by several nanometers.

In such case electron correlation can mediate energy transfer between the neighboring systems. In Förster energy transfer valence excitation energy is transferred from one system to its neighbor for example in proteins or in optical light emitting diodes. Higher energies are transferred after inner-valence ionization or excitation in one atom, leading to the ionization of its neighbor, a process known as the interatomic Coulombic decay (ICD). A related process is the interatomic Coulombic electron capture (ICEC) in which ionization of the neighbor is caused by electron capture of the initial atom. In our group we investigate these energy transfer processes with electron dynamics (ED) calculations. Thus we can trace the motion of all participating electrons on a pico- to femtosecond time scale and deduce from this information the velocity of the processes, the location the of electrons at every point in time, and the energies of each individual subsystem.

Currently we focus mainly on these processes being operative in arrays of quantum dots (QDs): Two neighboring semiconductor QDs can be theoretically described by two binding potentials containing a limited number of energetic levels and electrons. In such model potentials we observed ICD [1] and ICEC [2] with time resolution using electron dynamics calculations. We further postulate the use of the processes for next-generation QD infrared-photodetectors or QD solar cells as well as for the generation of monochromatic low-energy electrons.

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