Tim Wehling

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Low dimensional structures combine pronounced surface effects with distinct
many body interactions. Both affect material properties decisively, as they
determine excitations and boundaries between different electronic as well as
structural phases. Here, we discuss how the electronic structure of low
dimensional materials can be understood based on microscopic theory along
with three examples of how interactions affect material properties. First, we
consider chemically functionalized graphene and show how doping triggers
adsorbate phase transitions including tendencies towards sublattice symmetry
breaking. Regarding the electrons in layered materials, local "Hubbard
interactions" generally compete with large non-local Coulomb interactions. We
will discuss the "two-faced" nature of these non-local interactions: while they
contribute to strong renormalizations of electronic excitations, non-local
Coulomb terms turn out to weaken ground state electronic correlations
frequently. Finally, we will turn to quantum impurity problems and show how
electronic interactions shape excitation spectra in magnetic nanostructures.

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Universität Bremen
Seminarraum Theoretische Physik
Contact: not specified