@article{WiessnerRodriguezLastraZiroffetal.2012,
  author    = {Wiessner, M. and Rodriguez Lastra, N. S. and Ziroff, J. and Forster, F. and Puschnig, P. and D{\"o}ssel, L. and M{\"u}llen, K. and Sch{\"o}ll, A. and Reinert, F.},
  title     = {Different views on the electronic structure of nanoscale graphene: aromatic molecule versus quantum dot},
  series = {New Journal of Physics},
  volume    = {14},
  journal   = {New Journal of Physics},
  number    = {113008},
  doi       = {10.1088/1367-2630/14/11/113008},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130184},
  pages     = {12},
  year      = {2012},
  abstract  = {Graphene's peculiar electronic band structure makes it of interest for new electronic and spintronic approaches. However, potential applications suffer from quantization effects when the spatial extension reaches the nanoscale. We show by photoelectron spectroscopy on nanoscaled model systems (disc-shaped, planar polyacenes) that the two-dimensional band structure is transformed into discrete states which follow the momentum dependence of the graphene Bloch states. Based on a simple model of quantum wells, we show how the band structure of graphene emerges from localized states, and we compare this result with ab initio calculations which describe the orbital structure.},
  language  = {en}
}
@article{SessiSilkinNechaevetal.2015,
  author    = {Sessi, Paolo and Silkin, Vyacheslav M. and Nechaev, Ilya A. and Bathon, Thomas and El-Kareh, Lydia and Chulkov, Evgueni V. and Echenique, Pedro M. and Bode, Matthias},
  title     = {Direct observation of many-body charge density oscillations in a two-dimensional electron gas},
  series = {Nature Communications},
  volume    = {6},
  journal   = {Nature Communications},
  number    = {8691},
  doi       = {10.1038/ncomms9691},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145246},
  year      = {2015},
  abstract  = {Quantum interference is a striking manifestation of one of the basic concepts of quantum mechanics: the particle-wave duality. A spectacular visualization of this effect is the standing wave pattern produced by elastic scattering of surface electrons around defects, which corresponds to a modulation of the electronic local density of states and can be imaged using a scanning tunnelling microscope. To date, quantum-interference measurements were mainly interpreted in terms of interfering electrons or holes of the underlying band-structure description. Here, by imaging energy-dependent standing-wave patterns at noble metal surfaces, we reveal, in addition to the conventional surface-state band, the existence of an 'anomalous' energy band with a well-defined dispersion. Its origin is explained by the presence of a satellite in the structure of the many-body spectral function, which is related to the acoustic surface plasmon. Visualizing the corresponding charge oscillations provides thus direct access to many-body interactions at the atomic scale.},
  language  = {en}
}
@article{SauerWiessnerSchoelletal.2015,
  author    = {Sauer, C and Wießner, M and Sch{\"o}ll, A and Reinert, F},
  title     = {Observation of a molecule-metal interface charge transfer related feature by resonant photoelectron spectroscopy},
  series = {New Journal of Physics},
  volume    = {17},
  journal   = {New Journal of Physics},
  number    = {043016},
  doi       = {10.1088/1367-2630/17/4/043016},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148672},
  year      = {2015},
  abstract  = {We report the discovery of a charge transfer (CT) related low binding energy feature at a molecule-metal interface by the application of resonant photoelectron spectroscopy (RPES). This interface feature is neither present for molecular bulk samples nor for the clean substrate. A detailed analysis of the spectroscopic signature of the low binding energy feature shows characteristics of electronic interaction not found in other electron spectroscopic techniques. Within a cluster model description this feature is assigned to a particular eigenstate of the photoionized system that is invisible in direct photoelectron spectroscopy but revealed in RPES through a relative resonant enhancement. Interpretations based on considering only the predominant character of the eigenstates explain the low binding energy feature by an occupied lowest unoccupied molecular orbital, which is either realized through CT in the ground or in the intermediate state. This reveals that molecule-metal CT is responsible for this feature. Consequently, our study demonstrates the sensitivity of RPES to electronic interactions and constitutes a new way to investigate CT at molecule-metal interfaces.},
  language  = {en}
}